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search.xml
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<?xml version="1.0" encoding="utf-8"?>
<search>
<entry>
<title>JavaEE课程踩坑记录</title>
<link href="/2020/12/21/solving-problem/"/>
<url>/2020/12/21/solving-problem/</url>
<content type="html"><![CDATA[<h2 id="踩坑记录"><a href="#踩坑记录" class="headerlink" title="踩坑记录"></a>踩坑记录</h2><h4 id="1-数据库时区有关异常"><a href="#1-数据库时区有关异常" class="headerlink" title="1. 数据库时区有关异常"></a>1. 数据库时区有关异常</h4><ul><li>解决方案：添加时区参数<code>jdbc:mysql://localhost:3306/DATABASE?serverTimezone=UTC</code></li></ul><h4 id="2-更换Maven源"><a href="#2-更换Maven源" class="headerlink" title="2. 更换Maven源"></a>2. 更换Maven源</h4><ul><li>解决方案：在setting.xml中加入国内源</li></ul><a id="more"></a><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta"><?xml version="1.0" encoding="UTF-8"?></span></span><br><span class="line"><span class="tag"><<span class="name">settings</span> <span class="attr">xmlns</span>=<span class="string">"http://maven.apache.org/SETTINGS/1.0.0"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">mirrors</span>></span></span><br><span class="line"> <span class="comment"><!-- mirror</span></span><br><span class="line"><span class="comment"> | Specifies a repository mirror site to use instead of a given repository. The repository that</span></span><br><span class="line"><span class="comment"> | this mirror serves has an ID that matches the mirrorOf element of this mirror. IDs are used</span></span><br><span class="line"><span class="comment"> | for inheritance and direct lookup purposes, and must be unique across the set of mirrors.</span></span><br><span class="line"><span class="comment"> |</span></span><br><span class="line"><span class="comment"> <mirror></span></span><br><span class="line"><span class="comment"> <id>mirrorId</id></span></span><br><span class="line"><span class="comment"> <mirrorOf>repositoryId</mirrorOf></span></span><br><span class="line"><span class="comment"> <name>Human Readable Name for this Mirror.</name></span></span><br><span class="line"><span class="comment"> <url>http://my.repository.com/repo/path</url></span></span><br><span class="line"><span class="comment"> </mirror></span></span><br><span class="line"><span class="comment"> --></span></span><br><span class="line"></span><br><span class="line"> <span class="tag"><<span class="name">mirror</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">id</span>></span>alimaven<span class="tag"></<span class="name">id</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">name</span>></span>aliyun maven<span class="tag"></<span class="name">name</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">url</span>></span>http://maven.aliyun.com/nexus/content/groups/public/<span class="tag"></<span class="name">url</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">mirrorOf</span>></span>central<span class="tag"></<span class="name">mirrorOf</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">mirror</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="tag"><<span class="name">mirror</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">id</span>></span>uk<span class="tag"></<span class="name">id</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">mirrorOf</span>></span>central<span class="tag"></<span class="name">mirrorOf</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">name</span>></span>Human Readable Name for this Mirror.<span class="tag"></<span class="name">name</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">url</span>></span>http://uk.maven.org/maven2/<span class="tag"></<span class="name">url</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">mirror</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="tag"><<span class="name">mirror</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">id</span>></span>CN<span class="tag"></<span class="name">id</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">name</span>></span>OSChina Central<span class="tag"></<span class="name">name</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">url</span>></span>http://maven.oschina.net/content/groups/public/<span class="tag"></<span class="name">url</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">mirrorOf</span>></span>central<span class="tag"></<span class="name">mirrorOf</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">mirror</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="tag"><<span class="name">mirror</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">id</span>></span>nexus<span class="tag"></<span class="name">id</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">name</span>></span>internal nexus repository<span class="tag"></<span class="name">name</span>></span></span><br><span class="line"> <span class="comment"><!-- <url>http://192.168.1.100:8081/nexus/content/groups/public/</url>--></span></span><br><span class="line"> <span class="tag"><<span class="name">url</span>></span>http://repo.maven.apache.org/maven2<span class="tag"></<span class="name">url</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">mirrorOf</span>></span>central<span class="tag"></<span class="name">mirrorOf</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">mirror</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="tag"></<span class="name">mirrors</span>></span></span><br><span class="line"><span class="tag"></<span class="name">settings</span>></span></span><br></pre></td></tr></table></figure><h4 id="3-AOP后置通知和最终通知的顺序颠倒"><a href="#3-AOP后置通知和最终通知的顺序颠倒" class="headerlink" title="3. AOP后置通知和最终通知的顺序颠倒"></a>3. AOP后置通知和最终通知的顺序颠倒</h4><ul><li>解决方案：将<code>spring-context</code>版本设为<code>5.2.7.RELEASE</code></li></ul><h4 id="4-有关MyBatis"><a href="#4-有关MyBatis" class="headerlink" title="4. 有关MyBatis"></a>4. 有关MyBatis</h4><p>在<code>Mybatis</code>中的<code>mapper</code>中的<code>xml</code>文件中写<code>SQL</code>语句时，小于号以及大于号要写成<code>&lt;</code>以及<code>&gt;</code>否则会与<code>xml</code>中的尖括号冲突。</p><h4 id="5-有关微信小程序"><a href="#5-有关微信小程序" class="headerlink" title="5. 有关微信小程序"></a>5. 有关微信小程序</h4><p>在微信小程序中，要求使用<code>https</code>协议。在这里采取的方法是将后台应用部署到服务器上，并使用<code>nginx</code>进行反向代理。最后申请域名，上<code>https</code>证书。</p><p><code>nginx</code>的配置如下：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">server {</span><br><span class="line"> listen 443 ssl; #配置HTTPS的默认访问端口号为443。此处如果未配置HTTPS的默认访问端口，可能会造成Nginx无法启动。Nginx 1.15.0以上版本请使用listen 443 ssl代替listen 443和ssl on。</span><br><span class="line"> server_name wwww.kuumtde.cn; #将www.certificatestests.com修改为您证书绑定的域名，例如：www.example.com。如果您购买的是通配符域名证书，要修改为通配符域名，例如：*.aliyun.com。</span><br><span class="line"> root html;</span><br><span class="line"> index index.html index.htm;</span><br><span class="line"> ssl_certificate cert/4683033_kuumtde.cn.pem; #将domain name.pem替换成您证书的文件名称。</span><br><span class="line"> ssl_certificate_key cert/4683033_kuumtde.cn.key; #将domain name.key替换成您证书的密钥文件名称。</span><br><span class="line"> ssl_session_timeout 5m;</span><br><span class="line"> ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE:ECDH:AES:HIGH:!NULL:!aNULL:!MD5:!ADH:!RC4; #使用此加密套件。</span><br><span class="line"> ssl_protocols TLSv1 TLSv1.1 TLSv1.2; #使用该协议进行配置。</span><br><span class="line"> ssl_prefer_server_ciphers on;</span><br><span class="line"></span><br><span class="line"> location / {</span><br><span class="line"> root html; #站点目录。</span><br><span class="line"> index index.html index.htm;</span><br><span class="line"> proxy_pass http://127.0.0.1:8080;</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure><p>配置完成后，重启<code>nginx</code>即可</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="built_in">cd</span> /usr/<span class="built_in">local</span>/nginx/sbin</span><br><span class="line">./nginx -s stop</span><br><span class="line">./nginx</span><br></pre></td></tr></table></figure><p>或者重新加载配置文件也可：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">./nginx -s reload</span><br></pre></td></tr></table></figure><h4 id="6-服务端上项目的打包以及部署"><a href="#6-服务端上项目的打包以及部署" class="headerlink" title="6. 服务端上项目的打包以及部署"></a>6. 服务端上项目的打包以及部署</h4><p>首先进入项目目录，然后编译、打包、运行</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">mvn clean</span><br><span class="line">mvn compile</span><br><span class="line">mvn package</span><br><span class="line">nohup java -jar XXX.jar</span><br></pre></td></tr></table></figure>]]></content>
<categories>
<category> Spring </category>
</categories>
<tags>
<tag> Spring </tag>
<tag> Linux </tag>
<tag> Java </tag>
</tags>
</entry>
<entry>
<title>Linux环境配置常见问题</title>
<link href="/2020/12/02/linux-env/"/>
<url>/2020/12/02/linux-env/</url>
<content type="html"><![CDATA[<h1 id="Linux环境配置常见问题"><a href="#Linux环境配置常见问题" class="headerlink" title="Linux环境配置常见问题"></a>Linux环境配置常见问题</h1><h2 id="1-换清华源"><a href="#1-换清华源" class="headerlink" title="1. 换清华源"></a>1. 换清华源</h2><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">$ cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup <span class="comment">#备份</span></span><br><span class="line">$ vim /etc/yum.repos.d/CentOS-Base.repo <span class="comment">#将内容修改如下</span></span><br></pre></td></tr></table></figure><a id="more"></a><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br></pre></td><td class="code"><pre><span class="line"># CentOS-Base.repo</span><br><span class="line">#</span><br><span class="line"># The mirror system uses the connecting IP address of the client and the</span><br><span class="line"># update status of each mirror to pick mirrors that are updated to and</span><br><span class="line"># geographically close to the client. You should use this for CentOS updates</span><br><span class="line"># unless you are manually picking other mirrors.</span><br><span class="line">#</span><br><span class="line"># If the mirrorlist= does not work for you, as a fall back you can try the</span><br><span class="line"># remarked out baseurl= line instead.</span><br><span class="line">#</span><br><span class="line">#</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">[base]</span><br><span class="line">name=CentOS-$releasever - Base</span><br><span class="line">baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos/$releasever/os/$basearch/</span><br><span class="line">#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os</span><br><span class="line">enabled=1</span><br><span class="line">gpgcheck=1</span><br><span class="line">gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-7</span><br><span class="line"></span><br><span class="line">#released updates</span><br><span class="line">[updates]</span><br><span class="line">name=CentOS-$releasever - Updates</span><br><span class="line">baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos/$releasever/updates/$basearch/</span><br><span class="line">#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates</span><br><span class="line">enabled=1</span><br><span class="line">gpgcheck=1</span><br><span class="line">gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-7</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">#additional packages that may be useful</span><br><span class="line">[extras]</span><br><span class="line">name=CentOS-$releasever - Extras</span><br><span class="line">baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos/$releasever/extras/$basearch/</span><br><span class="line">#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras</span><br><span class="line">enabled=1</span><br><span class="line">gpgcheck=1</span><br><span class="line">gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-7</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">#additional packages that extend functionality of existing packages</span><br><span class="line">[centosplus]</span><br><span class="line">name=CentOS-$releasever - Plus</span><br><span class="line">baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos/$releasever/centosplus/$basearch/</span><br><span class="line">#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus</span><br><span class="line">gpgcheck=1</span><br><span class="line">enabled=0</span><br><span class="line">gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-7</span><br></pre></td></tr></table></figure><p>这里是<a href="https://mirrors.tuna.tsinghua.edu.cn/help/centos/" target="_blank" rel="noopener">参考网址</a></p><h2 id="2-配置环境变量"><a href="#2-配置环境变量" class="headerlink" title="2. 配置环境变量"></a>2. 配置环境变量</h2><p>在<code>/etc/profile</code>下修改环境变量<br>举例：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">export CMAKE_HOME=/usr/local/cmake-3.18.4-Linux-x86_64</span><br><span class="line">export PATH=$CMAKE_HOME/bin:$PATH</span><br></pre></td></tr></table></figure><p>使用<code>source /etc/profile</code>命令更新环境变量</p><h2 id="3-网络配置"><a href="#3-网络配置" class="headerlink" title="3. 网络配置"></a>3. 网络配置</h2><p> 配置文件位置：<code>cd /etc/sysconfig/network-scripts</code></p><p>配置完成后，重启网络服务<br><code>systemctl restart network.service</code></p><h2 id="4-防火墙"><a href="#4-防火墙" class="headerlink" title="4. 防火墙"></a>4. 防火墙</h2><p>查看防火墙状态：<code>systemctl status firewalld</code></p><p>关闭防火墙：<code>systemctl stop firewalld.service</code></p><p>开放端口：<code>firewall-cmd --zone=public --add-port=5672/tcp --permanent</code></p><p>关闭端口：<code>firewall-cmd --zone=public --remove-port=5672/tcp --permanent</code></p><p>使配置立即生效：<code>firewall-cmd --reload</code></p><h2 id="5-赋予用户sudo权限"><a href="#5-赋予用户sudo权限" class="headerlink" title="5. 赋予用户sudo权限"></a>5. 赋予用户sudo权限</h2><p>修改<code>/etc/sudoers</code>文件 </p><p>加入以下内容</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">username ALL=(ALL) ALL</span><br></pre></td></tr></table></figure>]]></content>
<categories>
<category> Linux </category>
</categories>
<tags>
<tag> Linux </tag>
</tags>
</entry>
<entry>
<title>SpringMVC——文件上传、异常处理、拦截器</title>
<link href="/2020/11/11/springmvc2/"/>
<url>/2020/11/11/springmvc2/</url>
<content type="html"><![CDATA[<h1 id="SpringMVC——文件上传、异常处理、拦截器"><a href="#SpringMVC——文件上传、异常处理、拦截器" class="headerlink" title="SpringMVC——文件上传、异常处理、拦截器"></a>SpringMVC——文件上传、异常处理、拦截器</h1><h2 id="1-异常处理"><a href="#1-异常处理" class="headerlink" title="1. 异常处理"></a>1. 异常处理</h2><p>系统中异常包括两类：预期异常和运行时异常 <code>RuntimeException</code>，前者通过捕获异常从而获取异常信息， 后者主要通过规范代码开发、测试通过手段减少运行时异常的发生。 系统的 dao、service、controller 出现都通过 <code>throws Exception</code>向上抛出，最后由 <code>springmvc</code> 前端 控制器交由异常处理器进行异常处理。</p><h3 id="1-处理方式1"><a href="#1-处理方式1" class="headerlink" title="1. 处理方式1"></a>1. 处理方式1</h3><p>自定义异常处理类，并实现<code>HandlerExceptionResolver</code>接口。</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Component</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">SysExceptionResolver</span> <span class="keyword">implements</span> <span class="title">HandlerExceptionResolver</span> </span>{</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> ModelAndView <span class="title">resolveException</span><span class="params">(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e)</span> </span>{</span><br><span class="line"> <span class="comment">//获取异常</span></span><br><span class="line"> SysException ex = <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">if</span>(e <span class="keyword">instanceof</span> SysException){</span><br><span class="line"> ex = (SysException) e;</span><br><span class="line"> }<span class="keyword">else</span>{</span><br><span class="line"> ex = <span class="keyword">new</span> SysException(<span class="string">"系统正在维护"</span>);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//创建ModelAndView对象</span></span><br><span class="line"> ModelAndView mv= <span class="keyword">new</span> ModelAndView();</span><br><span class="line"> mv.addObject(<span class="string">"errorMsg"</span>,e.getMessage());</span><br><span class="line"> mv.setViewName(<span class="string">"error"</span>);</span><br><span class="line"> <span class="keyword">return</span> mv;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><a id="more"></a><h3 id="2-处理方式"><a href="#2-处理方式" class="headerlink" title="2. 处理方式"></a>2. 处理方式</h3><p>使用<code>@ExceptionHandler</code>注解加在方法上，处理异常。</p><p>另外，可以在异常处理类上加上<code>@ControllerAdvice</code>，用来处理控制器的全局配置。</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@ResponseBody</span></span><br><span class="line"><span class="meta">@ControllerAdvice</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">CustmomizeExceptionHandler</span> </span>{</span><br><span class="line"> <span class="meta">@ExceptionHandler</span>(Exception<span class="class">.<span class="keyword">class</span>)</span></span><br><span class="line"><span class="class"> <span class="title">Object</span> <span class="title">handleControllerException</span>(<span class="title">HttpServletRequest</span> <span class="title">request</span>, <span class="title">Throwable</span> <span class="title">e</span>, <span class="title">Model</span> <span class="title">model</span>) </span>{</span><br><span class="line"></span><br><span class="line"> String contentType = request.getContentType();</span><br><span class="line"></span><br><span class="line"> <span class="keyword">if</span> (<span class="string">"application/json"</span>.equals(contentType)) {</span><br><span class="line"> <span class="comment">//返回json</span></span><br><span class="line"> <span class="keyword">if</span> (e <span class="keyword">instanceof</span> CustomizeException) {</span><br><span class="line"> <span class="keyword">return</span> ResultDTO.errorOf((CustomizeException)e);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">return</span> ResultDTO.errorOf(CustomizeErrorCode.SYSTEM_ERROR);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">//错误页面详情</span></span><br><span class="line"> <span class="keyword">if</span> (e <span class="keyword">instanceof</span> CustomizeException) {</span><br><span class="line"> model.addAttribute(<span class="string">"message"</span>, e.getMessage());</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> model.addAttribute(<span class="string">"message"</span>, CustomizeErrorCode.SYSTEM_ERROR.getMessage());</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> ModelAndView(<span class="string">"error"</span>);</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure><h2 id="2-拦截器"><a href="#2-拦截器" class="headerlink" title="2. 拦截器"></a>2. 拦截器</h2><p>拦截器可以对控制器的方法进行预处理或后处理。</p><p><code>preHandler</code>：在<code>controller</code>方法前执行。如果返回<code>true</code>，放行执行控制器方法，否则不放行。</p><p><code>postHandler</code>：在<code>controller</code>方法执行后执行。</p><p><code>afterHandler</code>：前端控制器完全处理完请求后再执行。</p><p>编写代码时，需要实现<code>HandlerInterceptor</code>接口。</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">MyInterceptor1</span> <span class="keyword">implements</span> <span class="title">HandlerInterceptor</span> </span>{</span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> request</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> response</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> handler</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@return</span> 如果为true，放行，执行controller方法，否则不放行</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@throws</span> Exception</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">boolean</span> <span class="title">preHandle</span><span class="params">(HttpServletRequest request, HttpServletResponse response, Object handler)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> System.out.println(<span class="string">"MyInterceptor1执行了"</span>);</span><br><span class="line"> request.getRequestDispatcher(<span class="string">"/WEB-INF/pages/error.jsp"</span>).forward(request, response);</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">true</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * controller方法执行后</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> request</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> response</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> handler</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> modelAndView</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@throws</span> Exception</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">postHandle</span><span class="params">(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> System.out.println(<span class="string">"MyInterceptor1执行后"</span>);</span><br><span class="line"><span class="comment">// request.getRequestDispatcher("/WEB-INF/pages/error.jsp").forward(request, response);</span></span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * success.jsp页面执行后，该方法执行</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> request</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> response</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> handler</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> ex</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@throws</span> Exception</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">afterCompletion</span><span class="params">(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"> System.out.println(<span class="string">"最后"</span>);</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>配置拦截器时，可以在<code>xml</code>文件中配置：</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">mvc:interceptors</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">mvc:interceptor</span>></span></span><br><span class="line"> <span class="comment"><!--要拦截的具体方法--></span></span><br><span class="line"> <span class="tag"><<span class="name">mvc:mapping</span> <span class="attr">path</span>=<span class="string">"/user/*"</span>/></span></span><br><span class="line"> <span class="comment"><!--配置拦截器对象--></span></span><br><span class="line"> <span class="tag"><<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"myInterceptor1"</span> <span class="attr">class</span>=<span class="string">"com.billychen.interceptor.MyInterceptor1"</span>></span><span class="tag"></<span class="name">bean</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">mvc:interceptor</span>></span></span><br><span class="line"><span class="tag"></<span class="name">mvc:interceptors</span>></span></span><br></pre></td></tr></table></figure><p>也可以在<code>Java</code>配置类中配置</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">WebConfig</span> <span class="keyword">implements</span> <span class="title">WebMvcConfigurer</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Autowired</span></span><br><span class="line"> <span class="keyword">private</span> SessionInterceptor sessionInterceptor;</span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">addInterceptors</span><span class="params">(InterceptorRegistry registry)</span> </span>{</span><br><span class="line"> registry.addInterceptor(sessionInterceptor).addPathPatterns(<span class="string">"/**"</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h2 id="3-文件上传"><a href="#3-文件上传" class="headerlink" title="3. 文件上传"></a>3. 文件上传</h2><p><code>Spring MVC</code>可以为我们简化文件的上传，使用<code>MultipartFile</code>对象来获得上传的文件。</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping</span>(<span class="string">"/fileUpload2"</span>)</span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">fileUpload2</span><span class="params">(HttpServletRequest request, MultipartFile upload)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> System.out.println(<span class="string">"file upload2"</span>);</span><br><span class="line"> <span class="comment">//使用fileupload组件完成文件上传</span></span><br><span class="line"> <span class="comment">//上传位置</span></span><br><span class="line"> String path = request.getSession().getServletContext().getRealPath(<span class="string">"/upload/"</span>);</span><br><span class="line"> <span class="comment">//判断该路径是否存在</span></span><br><span class="line"> File file = <span class="keyword">new</span> File(path);</span><br><span class="line"> <span class="keyword">if</span> (!file.exists()) {</span><br><span class="line"> file.mkdirs();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> String filename = upload.getOriginalFilename();</span><br><span class="line"> <span class="comment">//把文件名称设置成唯一值</span></span><br><span class="line"> String uuid = UUID.randomUUID().toString().replace(<span class="string">"-"</span>, <span class="string">""</span>);</span><br><span class="line"> filename = uuid + <span class="string">"_"</span> + filename;</span><br><span class="line"> <span class="comment">//上传文件</span></span><br><span class="line"> upload.transferTo(<span class="keyword">new</span> File(path, filename));</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> <span class="string">"success"</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>在<code>xml</code>中需要配置文件解析器</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment"><!--配置文件解析器--></span></span><br><span class="line"><span class="comment"><!--id必须为multipartResolver--></span></span><br><span class="line"><span class="tag"><<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"multipartResolver"</span> <span class="attr">class</span>=<span class="string">"org.springframework.web.multipart.commons.CommonsMultipartResolver"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"maxUploadSize"</span> <span class="attr">value</span>=<span class="string">"10485760"</span>></span><span class="tag"></<span class="name">property</span>></span></span><br><span class="line"><span class="tag"></<span class="name">bean</span>></span></span><br></pre></td></tr></table></figure><p>注意：在<code>Spring Boot</code>中已经自动配置文件解析器，如果需要自动配置，可以在配置类中自行配置自定义的文件解析器。</p>]]></content>
<categories>
<category> Spring </category>
</categories>
<tags>
<tag> Spring </tag>
<tag> Java </tag>
<tag> SpringMVC </tag>
</tags>
</entry>
<entry>
<title>SpringMVC——参数和返回值</title>
<link href="/2020/11/11/springmvc1/"/>
<url>/2020/11/11/springmvc1/</url>
<content type="html"><![CDATA[<h1 id="Spring-MVC——参数和返回值"><a href="#Spring-MVC——参数和返回值" class="headerlink" title="Spring MVC——参数和返回值"></a>Spring MVC——参数和返回值</h1><h2 id="0-介绍"><a href="#0-介绍" class="headerlink" title="0. 介绍"></a>0. 介绍</h2><p>SpringMVC 是一种基于<code>Java</code>的实现MVC设计模型的请求驱动类型的轻量级 Web 框架，属于 <code>Spring FrameWork</code>的后续产品，已经融合在 <code>Spring Web Flow</code>里面。<code>Spring</code> 框架提供了构建 Web 应用程序的全功能 MVC 模块。</p><p>它通过一套注解，让一个简单的<code>Java</code>类成为处理请求的控制器，而无须实现任何接口。同时它还支<code>持RESTful</code>编程风格的请求。 </p><img src="/2020/11/11/springmvc1/springmvc.png" class="" title="SpringMVC"><p><code>Spring MVC</code>的执行流程如下</p><img src="/2020/11/11/springmvc1/process.png" class="" title="执行流程"><h2 id="1-常用注解"><a href="#1-常用注解" class="headerlink" title="1. 常用注解"></a>1. 常用注解</h2><p><code>@RequestMapping</code>：建立请求URL和处理方法之间的对应关系，作用在类或者方法上。</p><p><code>@RequestParam</code>：把请求中的指定名称的参数传递给控制器中的形参赋值</p><p>举例：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping</span>(<span class="string">"/useRequestParam"</span>)</span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">useRequestParam</span><span class="params">(@RequestParam(<span class="string">"name"</span>)</span>String username,</span></span><br><span class="line"><span class="function"> @<span class="title">RequestParam</span><span class="params">(value=<span class="string">"age"</span>,required=<span class="keyword">false</span>)</span> Integer age)</span>{</span><br><span class="line"> System.out.println(username+<span class="string">","</span>+age);</span><br><span class="line"> <span class="keyword">return</span> <span class="string">"success"</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p><code>@RequestBody</code>：直接以<code>key=value</code>的形式获取请求体内容（<code>String</code>类型）或者<code>Java</code>对象。用于<code>POST</code>请求。</p><p><code>@PathVaribale</code>：用于绑定 url中的占位符。例如：请求 url 中 <code>/delete/{id}</code>，这个<code>{id}</code>就是 url 占位符。</p><p><code>@ModelAttribute</code>：出现在方法上，表示当前方法会在控制器方法之前执行。也可以出现在参数上，获取指定的数据给参数赋值。</p><p>应用场景：当表单提交数据不是完整的实体类数据时，保证没有提交数据的字段使用数据库对象原来的数据。</p><a id="more"></a><p>举例：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="meta">@RequestMapping</span>(<span class="string">"modelAtrributionByObject"</span>)</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ModelAtrributionByObject</span> </span>{</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> <span class="meta">@ModelAttribute</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> User <span class="title">showModel</span><span class="params">(String userName)</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"showModel中接收的参数userName:"</span>+userName);</span><br><span class="line"> <span class="comment">//模拟去数据库查询</span></span><br><span class="line"> User user = findUserByName(userName);</span><br><span class="line"> System.out.println(<span class="string">"执行了 showModel 方法"</span> + user);</span><br><span class="line"> <span class="keyword">return</span> user;</span><br><span class="line"><span class="comment">// return;</span></span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 模拟修改用户方法</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> user</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@return</span></span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="meta">@RequestMapping</span>(<span class="string">"/updateUser"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">public</span> String <span class="title">testModelAttribute</span><span class="params">(User user)</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"控制器中处理请求的方法：修改用户："</span> + user);</span><br><span class="line"> <span class="keyword">return</span> <span class="string">"success"</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 模拟去数据库查询</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> userName</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@return</span></span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="function"><span class="keyword">private</span> User <span class="title">findUserByName</span><span class="params">(String userName)</span> </span>{</span><br><span class="line"> User user = <span class="keyword">new</span> User();</span><br><span class="line"> user.setUserName(<span class="string">"数据库中的姓名"</span>);</span><br><span class="line"> user.setAge(<span class="number">19</span>);</span><br><span class="line"> user.setPassword(<span class="string">"123456"</span>);</span><br><span class="line"> <span class="keyword">return</span> user;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="meta">@RequestMapping</span>(<span class="string">"modelAtrributionByMap"</span>)</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ModelAtrributionByMap</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="meta">@ModelAttribute</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">showModel</span><span class="params">(String userName, Map<String, User> map)</span> </span>{</span><br><span class="line"> <span class="comment">//模拟去数据库查询</span></span><br><span class="line"> User user = findUserByName(userName);</span><br><span class="line"> System.out.println(<span class="string">"执行了 showModel 方法"</span> + user);</span><br><span class="line"> map.put(<span class="string">"abc"</span>, user);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 模拟修改用户方法</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> user</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@return</span></span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="meta">@RequestMapping</span>(<span class="string">"/updateUser"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">public</span> String <span class="title">testModelAttribute</span><span class="params">(@ModelAttribute(<span class="string">"abc"</span>)</span> User user) </span>{</span><br><span class="line"> System.out.println(<span class="string">"控制器中处理请求的方法：修改用户："</span> + user);</span><br><span class="line"> <span class="keyword">return</span> <span class="string">"success"</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> User <span class="title">findUserByName</span><span class="params">(String userName)</span> </span>{</span><br><span class="line"> User user = <span class="keyword">new</span> User();</span><br><span class="line"> user.setUserName(userName);</span><br><span class="line"> user.setAge(<span class="number">19</span>);</span><br><span class="line"> user.setPassword(<span class="string">"123456"</span>);</span><br><span class="line"> <span class="keyword">return</span> user;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p><code>@SessionAttribute</code>：用于多次执行控制器方法间的参数共享。 <code>value</code>为存入属性的名称，<code>type</code>为存入属性的类型。</p><h2 id="2-数据响应"><a href="#2-数据响应" class="headerlink" title="2.数据响应"></a>2.数据响应</h2><h3 id="1-返回字符串"><a href="#1-返回字符串" class="headerlink" title="1. 返回字符串"></a>1. 返回字符串</h3><p><code>controller</code> 方法返回字符串可以指定逻辑视图名，通过视图解析器解析为物理视图地址。 </p><p>视图解析器的配置：</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment"><!-- 配置视图解析器 --></span></span><br><span class="line"> <span class="tag"><<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"viewResolver"</span> <span class="attr">class</span>=<span class="string">"org.springframework.web.servlet.view.InternalResourceViewResolver"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"prefix"</span> <span class="attr">value</span>=<span class="string">"/WEB-INF/pages/"</span>></span><span class="tag"></<span class="name">property</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"suffix"</span> <span class="attr">value</span>=<span class="string">".jsp"</span>></span><span class="tag"></<span class="name">property</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">bean</span>></span></span><br></pre></td></tr></table></figure><h3 id="2-返回空值（使用原生Servlet）"><a href="#2-返回空值（使用原生Servlet）" class="headerlink" title="2. 返回空值（使用原生Servlet）"></a>2. 返回空值（使用原生Servlet）</h3><ol><li>转发<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">request.getRequestDispatcher(<span class="string">"/WEB-INF/pages/success.jsp"</span>).forward(request,response);</span><br></pre></td></tr></table></figure>（此外，如果不使用原生<code>Servlet</code>，<code>SpringMVC</code>也提供了转发的方式）<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">return</span> <span class="string">"forward:/WEB-INF/pages/success.jsp"</span>;</span><br></pre></td></tr></table></figure></li><li>重定向<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">response.sendRedirect(request.getContextPath()+<span class="string">"/index.jsp"</span>);</span><br></pre></td></tr></table></figure>（此外，如果不使用原生<code>Servlet</code>，<code>SpringMVC</code>也提供了重定向的方式）<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">return</span> <span class="string">""</span>redirect:/index.jsp<span class="string">";</span></span><br></pre></td></tr></table></figure></li><li>通过<code>response</code>指定响应结果<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">response.setCharacterEncoding(<span class="string">"utf-8"</span>);</span><br><span class="line">response.setContentType(<span class="string">"application/json;charset=utf-8"</span>);</span><br><span class="line">response.getWriter().print(<span class="string">"你好"</span>);</span><br></pre></td></tr></table></figure></li></ol><h3 id="3-返回ModelAndView"><a href="#3-返回ModelAndView" class="headerlink" title="3. 返回ModelAndView"></a>3. 返回ModelAndView</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//加入数据</span></span><br><span class="line">modelAndView.addObject(<span class="string">"users"</span>,users);</span><br><span class="line">指定跳转页面的名字</span><br><span class="line">modelAndView.setViewName(<span class="string">"list"</span>);</span><br><span class="line"><span class="keyword">return</span> modelAndView;</span><br></pre></td></tr></table></figure><h3 id="4-返回Json（常用于前后端分离项目）"><a href="#4-返回Json（常用于前后端分离项目）" class="headerlink" title="4. 返回Json（常用于前后端分离项目）"></a>4. 返回Json（常用于前后端分离项目）</h3><p>使用<code>ResponseBody</code>注解，将<code>Java</code>对象转化为<code>Json</code>字符串</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping</span>(<span class="string">"/testAjax"</span>)</span><br><span class="line"><span class="meta">@ResponseBody</span> </span><br><span class="line"><span class="function"><span class="keyword">public</span> User <span class="title">testAjax</span><span class="params">(@RequestBody User user)</span></span>{</span><br><span class="line"> System.out.println(<span class="string">"testAjax方法执行了...."</span>);</span><br><span class="line"> System.out.println(user);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//做响应</span></span><br><span class="line"> user.setUsername(<span class="string">"feng"</span>);</span><br><span class="line"> user.setMoney(<span class="number">1000f</span>);</span><br><span class="line"> <span class="comment">//返回</span></span><br><span class="line"> <span class="keyword">return</span> user;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<categories>
<category> Spring </category>
</categories>
<tags>
<tag> Spring </tag>
<tag> Java </tag>
<tag> SpringMVC </tag>
</tags>
</entry>
<entry>
<title>Mybatis笔记</title>
<link href="/2020/11/11/mybatis-note/"/>
<url>/2020/11/11/mybatis-note/</url>
<content type="html"><![CDATA[<h1 id="MyBatis笔记"><a href="#MyBatis笔记" class="headerlink" title="MyBatis笔记"></a>MyBatis笔记</h1><h2 id="0-概述"><a href="#0-概述" class="headerlink" title="0. 概述"></a>0. 概述</h2><p><code>Mybatis</code>是一个优秀的基于<code>Java</code>的持久层框架，它内部封装了<code>jdbc</code>，使开发者只需要关注sql语句本身，而不需要花费精力去处理加载驱动、创建连接、创建 <code>statement</code>等繁杂的过程。</p><p><strong>官方网站</strong>：<a href="https://mybatis.org/mybatis-3/zh/index.html" target="_blank" rel="noopener">https://mybatis.org/mybatis-3/zh/index.html</a></p><p><code>Mybatis</code>通过<code>xml</code>或注解的方式将要执行的各种<code>statement</code>配置起来，并通过<code>Java</code>对象和<code>statement</code> 中 <code>sql</code>的动态参数进行映射生成最终执行的 <code>sql</code>语句，最后由 <code>Mybatis</code> 框架执行 <code>sql</code>并将结果映射为 <code>java</code> 对象并 返回。</p><h2 id="1-配置文件"><a href="#1-配置文件" class="headerlink" title="1. 配置文件"></a>1. 配置文件</h2><h2 id="1-主配置文件"><a href="#1-主配置文件" class="headerlink" title="1. 主配置文件"></a>1. 主配置文件</h2><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta"><?xml version="1.0" encoding="UTF-8"?></span></span><br><span class="line"><span class="meta"><!DOCTYPE <span class="meta-keyword">configuration</span></span></span><br><span class="line"><span class="meta"> <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Config 3.0//EN"</span></span></span><br><span class="line"><span class="meta"> <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-config.dtd"</span>></span></span><br><span class="line"><span class="tag"><<span class="name">configuration</span>></span></span><br><span class="line"> <span class="comment"><!--引入外部的properties文件，指定一些属性值--></span></span><br><span class="line"> <span class="tag"><<span class="name">properties</span> <span class="attr">resource</span>=<span class="string">"jdbcConfig.properties"</span>></span><span class="tag"></<span class="name">properties</span>></span></span><br><span class="line"> <span class="comment"><!--取类的别名--></span></span><br><span class="line"> <span class="tag"><<span class="name">typeAliases</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">typeAlias</span> <span class="attr">type</span>=<span class="string">"com.billychen.domain.User"</span> <span class="attr">alias</span>=<span class="string">"User"</span>></span><span class="tag"></<span class="name">typeAlias</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">typeAlias</span> <span class="attr">type</span>=<span class="string">"com.billychen.domain.Account"</span> <span class="attr">alias</span>=<span class="string">"Account"</span>></span><span class="tag"></<span class="name">typeAlias</span>></span></span><br><span class="line"> <span class="comment"><!--以下是批量别名方式，直接给出扫描包下的所有类，别名为类名--></span></span><br><span class="line"> <span class="tag"><<span class="name">package</span> <span class="attr">name</span>=<span class="string">"com.billychen.domain"</span>/></span> </span><br><span class="line"> <span class="tag"></<span class="name">typeAliases</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="comment"><!--配置环境--></span></span><br><span class="line"> <span class="tag"><<span class="name">environments</span> <span class="attr">default</span>=<span class="string">"mysql"</span>></span></span><br><span class="line"> <span class="comment"><!--配置mysql环境--></span></span><br><span class="line"> <span class="tag"><<span class="name">environment</span> <span class="attr">id</span>=<span class="string">"mysql"</span>></span></span><br><span class="line"> <span class="comment"><!--配置事务类型--></span></span><br><span class="line"> <span class="tag"><<span class="name">transactionManager</span> <span class="attr">type</span>=<span class="string">"JDBC"</span>></span><span class="tag"></<span class="name">transactionManager</span>></span></span><br><span class="line"> <span class="comment"><!--配置数据源（连接池）--></span></span><br><span class="line"> <span class="tag"><<span class="name">dataSource</span> <span class="attr">type</span>=<span class="string">"POOLED"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"driver"</span> <span class="attr">value</span>=<span class="string">"${jdbc.driver}"</span>/></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"url"</span> <span class="attr">value</span>=<span class="string">"${jdbc.url}"</span>/></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"username"</span> <span class="attr">value</span>=<span class="string">"${jdbc.username}"</span>/></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"password"</span> <span class="attr">value</span>=<span class="string">"${jdbc.password}"</span>/></span></span><br><span class="line"> <span class="tag"></<span class="name">dataSource</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">environment</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">environments</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="tag"><<span class="name">mappers</span>></span></span><br><span class="line"> <span class="comment"><!--<mapper resource="com/billychen/dao/IUserDao.xml"></mapper>--></span></span><br><span class="line"> <span class="comment"><!--指定dao接口所在的包，不需要再写mapper标签了--></span></span><br><span class="line"> <span class="tag"><<span class="name">package</span> <span class="attr">name</span>=<span class="string">"com.billychen.dao"</span>></span><span class="tag"></<span class="name">package</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">mappers</span>></span></span><br><span class="line"><span class="tag"></<span class="name">configuration</span>></span></span><br></pre></td></tr></table></figure><a id="more"></a><h2 id="2-和Dao类对应的XML文件"><a href="#2-和Dao类对应的XML文件" class="headerlink" title="2.和Dao类对应的XML文件"></a>2.和Dao类对应的XML文件</h2><p>此处给出一个例子，给出<code>IUserDao.java</code>和<code>IUserDao.xml</code>文件</p><p>以下是<code>Java</code>代码</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">IUserDao</span> </span>{</span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 查询所有,同时获取到用户的所有账户</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@return</span></span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="function">List<User> <span class="title">findAll</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 根据id查询用户</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@param</span> id</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@return</span></span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="function">User <span class="title">findById</span><span class="params">(Integer id)</span></span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>以下是对应的配置文件</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta"><?xml version="1.0" encoding="UTF-8" ?></span></span><br><span class="line"><span class="meta"><!DOCTYPE <span class="meta-keyword">mapper</span></span></span><br><span class="line"><span class="meta"> <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Mapper 3.0//EN"</span></span></span><br><span class="line"><span class="meta"> <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-mapper.dtd"</span>></span></span><br><span class="line"><span class="tag"><<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.billychen.dao.IUserDao"</span>></span></span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> <span class="comment"><!--resultMap标签用于实体类属性名和列名的对应--></span></span><br><span class="line"> <span class="comment"><!--如果使用resultMap 之后的resultType也要改为resultType--></span></span><br><span class="line"> <span class="comment"><!--<resultMap id="userMap" type="com.billychen.domain.User">--></span></span><br><span class="line"> <span class="comment"><!--</resultMap>--></span></span><br><span class="line"> <span class="tag"><<span class="name">resultMap</span> <span class="attr">id</span>=<span class="string">"userAccountMap"</span> <span class="attr">type</span>=<span class="string">"User"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">id</span> <span class="attr">property</span>=<span class="string">"id"</span> <span class="attr">column</span>=<span class="string">"id"</span>></span><span class="tag"></<span class="name">id</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">result</span> <span class="attr">property</span>=<span class="string">"username"</span> <span class="attr">column</span>=<span class="string">"username"</span>></span><span class="tag"></<span class="name">result</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">result</span> <span class="attr">property</span>=<span class="string">"birthday"</span> <span class="attr">column</span>=<span class="string">"birthday"</span>></span><span class="tag"></<span class="name">result</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">result</span> <span class="attr">property</span>=<span class="string">"sex"</span> <span class="attr">column</span>=<span class="string">"sex"</span>></span><span class="tag"></<span class="name">result</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">result</span> <span class="attr">property</span>=<span class="string">"address"</span> <span class="attr">column</span>=<span class="string">"address"</span>></span><span class="tag"></<span class="name">result</span>></span></span><br><span class="line"> <span class="comment"><!--配置User对象中accounts集合的映射--></span></span><br><span class="line"> <span class="comment"><!--ofType是集合中元素的类型--></span></span><br><span class="line"> <span class="comment"><!--一对一用association，一对多用collection--></span></span><br><span class="line"> <span class="tag"><<span class="name">collection</span> <span class="attr">property</span>=<span class="string">"accounts"</span> <span class="attr">ofType</span>=<span class="string">"Account"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">id</span> <span class="attr">property</span>=<span class="string">"id"</span> <span class="attr">column</span>=<span class="string">"aid"</span>></span><span class="tag"></<span class="name">id</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">result</span> <span class="attr">property</span>=<span class="string">"uid"</span> <span class="attr">column</span>=<span class="string">"UID"</span>></span><span class="tag"></<span class="name">result</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">result</span> <span class="attr">property</span>=<span class="string">"money"</span> <span class="attr">column</span>=<span class="string">"MONEY"</span>></span><span class="tag"></<span class="name">result</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">collection</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">resultMap</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="tag"><<span class="name">select</span> <span class="attr">id</span>=<span class="string">"findAll"</span> <span class="attr">resultMap</span>=<span class="string">"userAccountMap"</span>></span></span><br><span class="line"> select user.*,account.ID as aid,account.UID,account.MONEY from user left outer join account on account.UID=user.id</span><br><span class="line"> <span class="tag"></<span class="name">select</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="tag"><<span class="name">select</span> <span class="attr">id</span>=<span class="string">"findById"</span> <span class="attr">resultType</span>=<span class="string">"com.billychen.domain.User"</span> <span class="attr">parameterType</span>=<span class="string">"java.lang.Integer"</span>></span></span><br><span class="line"> select * from user where id=#{id};</span><br><span class="line"> <span class="tag"></<span class="name">select</span>></span></span><br><span class="line"><span class="tag"></<span class="name">mapper</span>></span></span><br></pre></td></tr></table></figure><h2 id="3-延迟加载"><a href="#3-延迟加载" class="headerlink" title="3. 延迟加载"></a>3. 延迟加载</h2><p>查询账户(<code>Account</code>)信息并且关联查询用户(<code>User</code>)信息。如果先查询账户(<code>Account</code>)信息即可满足要 求，当我们需要查询用户(<code>User</code>)信息时再查询用户(<code>User</code>)信息。把对用户(<code>User</code>)信息的按需去查询就是延迟加载。</p><p>比如，在查询账户时，需要连带查询其所属的用户。如果使用延迟加载，那么在需要用到用户的时候才进行查询。具体的配置在配置文件<code>association</code>标签中修改如下：</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">association</span> <span class="attr">property</span>=<span class="string">"user"</span> <span class="attr">javaType</span>=<span class="string">"User"</span> <span class="attr">select</span>=<span class="string">"com.billychen.dao.IUserDao.findById"</span> <span class="attr">column</span>=<span class="string">"uid"</span>></span> <span class="tag"></<span class="name">association</span>></span></span><br></pre></td></tr></table></figure><p>其含义是，根据用户的<code>uid</code>这一列的值，去查询所属账户的<code>id</code>。</p><p>为了使延迟加载生效，还需要在主配置文件中配置</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">settings</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"lazyLoadingEnabled"</span> <span class="attr">value</span>=<span class="string">"true"</span>/></span></span><br><span class="line"><span class="tag"></<span class="name">settings</span>></span></span><br></pre></td></tr></table></figure><h2 id="4-一级缓存和二级缓存"><a href="#4-一级缓存和二级缓存" class="headerlink" title="4. 一级缓存和二级缓存"></a>4. 一级缓存和二级缓存</h2><h3 id="1-一级缓存"><a href="#1-一级缓存" class="headerlink" title="1. 一级缓存"></a>1. 一级缓存</h3><p>一级缓存是 <code>SqlSession</code> 范围的缓存，当调用 <code>SqlSession</code> 的修改，添加，删除，<code>commit()</code>，<code>close()</code>等方法时，就会清空一级缓存</p><p>比如：</p><p>第一次发起查询用户 <code>id</code> 为 1 的用户信息，先去找缓存中是否有 <code>id</code> 为 1 的用户信息，如果没有，从数据库查询用户信息。</p><p>得到用户信息，将用户信息存储到一级缓存中。</p><p>如果 <code>sqlSession</code> 去执行 <code>commi</code>t 操作（执行插入、更新、删除），清空 <code>SqlSession</code> 中的一级缓存，这样 做的目的为了让缓存中存储的是最新的信息，避免脏读。 第二次发起查询用户 <code>id</code> 为 1</p><p>的用户信息，先去找缓存中是否有 <code>id</code> 为 1 的用户信息，缓存中有，直接从缓存 中获取用户信息。</p><h3 id="2-二级缓存"><a href="#2-二级缓存" class="headerlink" title="2. 二级缓存"></a>2. 二级缓存</h3><p>二级缓存是 <code>mapper</code> 映射级别的缓存，多个 <code>SqlSession</code> 去操作同一个 <code>Mapper</code> 映射的 <code>sql</code> 语句，多个 <code>SqlSession</code> 可以共用二级缓存，二级缓存是跨 <code>SqlSession</code> 的。 </p><p>开启二级缓存:</p><ol><li>在<code>SqlMapConfig.xml</code>中开启<figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">settings</span>></span> </span><br><span class="line"> <span class="comment"><!-- 开启二级缓存的支持 --></span> </span><br><span class="line"> <span class="tag"><<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"cacheEnabled"</span> <span class="attr">value</span>=<span class="string">"true"</span>/></span></span><br><span class="line"><span class="tag"></<span class="name">settings</span>></span></span><br></pre></td></tr></table></figure></li><li>配置响应的<code>mapper</code>文件<figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.itheima.dao.IUserDao"</span>></span></span><br><span class="line"> <span class="comment"><!-- 开启二级缓存的支持 --></span> </span><br><span class="line"> <span class="tag"><<span class="name">cache</span>></span><span class="tag"></<span class="name">cache</span>></span></span><br><span class="line"><span class="tag"></<span class="name">mapper</span>></span></span><br></pre></td></tr></table></figure></li><li>配置<code>statement</code>上的<code>useCache</code>属性<figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">select</span> <span class="attr">id</span>=<span class="string">"findById"</span> <span class="attr">resultType</span>=<span class="string">"user"</span> <span class="attr">parameterType</span>=<span class="string">"int"</span> <span class="attr">useCache</span>=<span class="string">"true"</span>></span> </span><br><span class="line"> select * from user where id = #{uid} </span><br><span class="line"><span class="tag"></<span class="name">select</span>></span></span><br></pre></td></tr></table></figure></li></ol>]]></content>
<tags>
<tag> Spring </tag>
<tag> Mybatis </tag>
</tags>
</entry>
<entry>
<title>Spring——事务</title>
<link href="/2020/09/21/spring-tx/"/>
<url>/2020/09/21/spring-tx/</url>
<content type="html"><![CDATA[<h1 id="Spring——事务"><a href="#Spring——事务" class="headerlink" title="Spring——事务"></a>Spring——事务</h1><h2 id="1-基于XML的声明式事务控制"><a href="#1-基于XML的声明式事务控制" class="headerlink" title="1. 基于XML的声明式事务控制"></a>1. 基于XML的声明式事务控制</h2><ol><li><p>配置事务管理器</p></li><li><p>配置事务的通知</p><p> 属性<br> <code>id</code>: 事务通知的唯一标识<br> <code>transaction-manager</code>给事务通知提供一个事务管理器的引用</p></li><li><p>配置AOP中的切入点表达式</p></li><li><p>建立事务通知和切入点表达式的关系</p></li><li><p>配置事务的属性(在事务通知tx:advice标签内部配置)</p></li></ol><a id="more"></a><blockquote><p><code>isolation</code>：事务隔离界别，默认值<code>DEFAULT</code>，表示使用数据库的默认隔离级别</p><p><code>propagation</code>：指定传播行为默认值为<code>REQUIRED</code>，表示一定有事务（增删改的选择，而查询方法可选择<code>SUPPORTS</code>）</p><p><code>read-only</code>：指定事务是否只读，只有查询方法才能设置为<code>true</code>，默认值为<code>false</code><br><code>timeout</code>：指定事务的超时时间 默认值-1 永不超时</p><p><code>rollback-for</code>：指定一个异常，产生该异常时事务回滚，产生其他异常时不回滚。没有默认值，表示任何异常都回滚</p><p><code>no-rollback-for</code>：指定一个异常，产生该异常时事务不回滚，产生其他异常时事务回滚。没有默认值，表示任何异常都回滚</p></blockquote><p>以下是一个配置的例子</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"transactionManager"</span> <span class="attr">class</span>=<span class="string">"org.springframework.jdbc.datasource.DataSourceTransactionManager"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"dataSource"</span> <span class="attr">ref</span>=<span class="string">"dataSource"</span>></span><span class="tag"></<span class="name">property</span>></span></span><br><span class="line"><span class="tag"></<span class="name">bean</span>></span></span><br><span class="line"></span><br><span class="line"><span class="tag"><<span class="name">tx:advice</span> <span class="attr">id</span>=<span class="string">"txAdvice"</span> <span class="attr">transaction-manager</span>=<span class="string">"transactionManager"</span>></span></span><br><span class="line"> <span class="comment"><!--配置事务属性--></span></span><br><span class="line"> <span class="tag"><<span class="name">tx:attributes</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">tx:method</span> <span class="attr">name</span>=<span class="string">"*"</span> <span class="attr">propagation</span>=<span class="string">"REQUIRED"</span> <span class="attr">read-only</span>=<span class="string">"false"</span>/></span></span><br><span class="line"> <span class="comment"><!--通配符指以find开头的所有方法--></span></span><br><span class="line"> <span class="tag"><<span class="name">tx:method</span> <span class="attr">name</span>=<span class="string">"find*"</span> <span class="attr">propagation</span>=<span class="string">"SUPPORTS"</span> <span class="attr">read-only</span>=<span class="string">"true"</span>/></span></span><br><span class="line"> <span class="tag"></<span class="name">tx:attributes</span>></span></span><br><span class="line"><span class="tag"></<span class="name">tx:advice</span>></span></span><br><span class="line"></span><br><span class="line"><span class="tag"><<span class="name">aop:config</span>></span></span><br><span class="line"> <span class="comment"><!--配置切入点表达式--></span></span><br><span class="line"> <span class="tag"><<span class="name">aop:pointcut</span> <span class="attr">id</span>=<span class="string">"pt1"</span> <span class="attr">expression</span>=<span class="string">"execution(* com.billychen.service.impl.*.*(..))"</span>></span><span class="tag"></<span class="name">aop:pointcut</span>></span></span><br><span class="line"> <span class="comment"><!--建立切入点和事务通知的关系--></span></span><br><span class="line"> <span class="tag"><<span class="name">aop:advisor</span> <span class="attr">advice-ref</span>=<span class="string">"txAdvice"</span> <span class="attr">pointcut-ref</span>=<span class="string">"pt1"</span>></span><span class="tag"></<span class="name">aop:advisor</span>></span></span><br><span class="line"><span class="tag"></<span class="name">aop:config</span>></span></span><br></pre></td></tr></table></figure><h2 id="2-基于注解的配置"><a href="#2-基于注解的配置" class="headerlink" title="2.基于注解的配置"></a>2.基于注解的配置</h2><ol><li>配置事务管理器</li><li>开启<code>Spring</code>对注解事务的支持<figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">tx:annotation-driven</span> <span class="attr">transaction-manager</span>=<span class="string">"transactionManager"</span>></span><span class="tag"></<span class="name">tx:annotation-driven</span>></span></span><br></pre></td></tr></table></figure></li><li>在需要支持事务的地方（类或方法前）使用<code>@Transactional</code>注解。注解中的属性可以设置事务的属性（隔离级别、传播行为、只读等）</li></ol><h2 id="3-事务隔离级别和传播行为"><a href="#3-事务隔离级别和传播行为" class="headerlink" title="3.事务隔离级别和传播行为"></a>3.事务隔离级别和传播行为</h2><h3 id="1-隔离级别"><a href="#1-隔离级别" class="headerlink" title="1. 隔离级别"></a>1. 隔离级别</h3><ol><li>未提交读：可以读取未提交的数据</li><li>读写提交：只能读取已提交的数据，解决脏读问题（<code>Oracle</code>默认级别）</li><li>可重复读：只能读取其他事务提交修改后的数据，解决不可重复读问题（<code>MySQL</code>默认级别）</li><li>串行化：解决幻读问题</li></ol><h2 id="2-传播行为"><a href="#2-传播行为" class="headerlink" title="2.传播行为"></a>2.传播行为</h2><ol><li><code>REQUIRED</code>:如果当前没有事务，就新建一个事务，如果已经存在一个事务中，加入到这个事务中。一般的选择（默认值）</li><li><code>SUPPORTS</code>:支持当前事务，如果当前没有事务，就以非事务方式执行（没有事务）</li><li><code>MANDATORY</code>：使用当前的事务，如果当前没有事务，就抛出异常</li><li><code>REQUERS_NEW</code>:新建事务，如果当前在事务中，把当前事务挂起。</li><li><code>NOT_SUPPORTED</code>:以非事务方式执行操作，如果当前存在事务，就把当前事务挂起</li><li><code>NEVER</code>:以非事务方式运行，如果当前存在事务，抛出异常</li><li><code>NESTED</code>:如果当前存在事务，则在嵌套事务内执行。如果当前没有事务，则执行 <code>REQUIRED</code> 类似的操作。</li></ol>]]></content>
<categories>
<category> Spring </category>
</categories>
<tags>
<tag> Spring </tag>
<tag> Java </tag>
</tags>
</entry>
<entry>
<title>Spring——AOP</title>
<link href="/2020/09/17/spring-aop/"/>
<url>/2020/09/17/spring-aop/</url>
<content type="html"><![CDATA[<h1 id="Spring-AOP"><a href="#Spring-AOP" class="headerlink" title="Spring AOP"></a>Spring AOP</h1><h2 id="0-思想"><a href="#0-思想" class="headerlink" title="0. 思想"></a>0. 思想</h2><p>运用动态代理的方式对核心业务类的方法进行增强，对核心逻辑和非核心逻辑进行隔离，把非核心逻辑织入到核心业务逻辑之中。开发人员在开发时可以专注于核心业务逻辑，使各个业务逻辑之间的耦合度降低，提高程序的可复用性。</p><h2 id="1-AOP的术语和细节"><a href="#1-AOP的术语和细节" class="headerlink" title="1. AOP的术语和细节"></a>1. AOP的术语和细节</h2><ol><li><p><code>Jointpoint</code>（连接点）</p><p> 被拦截的方法，通常是业务层的所有方法。</p></li><li><p><code>Pointcut</code>（切入点）</p><p> 并不是所有业务层的方法都需要被拦截增强。那些需要被增强的方法是切入点。</p></li><li><p><code>Advice</code>（通知/增强）</p><p> 指拦截到的<code>Jointpoint</code>之后需要做的事情。通知包括前置通知、后置通知、异常通知、最终通知、环绕通知。</p></li><li><p><code>Taeget</code>（目标对象）</p><p> 被代理的对象。</p></li><li><p><code>Weaving</code>（织入）</p><p> 是指把增强应用到目标对象来创建代理对象的过程。</p></li><li><p><code>Proxy</code>（代理）</p><p> 一个类被<code>AOP</code>织入增强后，产生的一个结果代理类。</p></li><li><p><code>Aspect</code>（切面）</p><p> 是切入点和通知的结合。（需要手动配置）</p></li></ol><a id="more"></a><h2 id="2-XML配置AOP步骤"><a href="#2-XML配置AOP步骤" class="headerlink" title="2. XML配置AOP步骤"></a>2. XML配置AOP步骤</h2><ol><li><p>把通知<code>bean</code>交给<code>spring</code>管理</p></li><li><p>使用<code>app:config</code>标签表明开始<code>AOP</code>配置</p></li><li><p>使用<code>aop:aspect</code>标签表明开始配置切面</p><p> <code>id</code>:切面的唯一标识<br> <code>ref</code>:指定通知类bean的id</p></li><li><p>在<code>aop:aspect</code>标签内部使用对应标签来配置通知的类型,比如<code>aop:before</code>表示配置前置通知。<br><code>method</code>属性用于指定通知类中哪个方法是前置通知<br><code>pointcut</code>属性用于指定切入点表达式，表示对业务层哪些方法增强</p></li><li><p>切入点表达式写法：</p><ul><li><p>关键字：<code>execution(表达式)</code></p></li><li><p>表达式：访问修饰符 返回值 全限定类名.方法名(参数列表)</p></li><li><p>标准写法：<code>public void com.billychen.service.impl.AccountServiceImpl.saveAccount()</code></p></li><li><p>访问修饰符可以省略 <code>void com.billychen.service.impl.AccountServiceImpl.saveAccount()</code></p></li><li><p>返回值可以使用通配符，表示任意返回值 <code>* com.billychen.service.impl.AccountServiceImpl.saveAccount()</code></p></li><li><p>包名可以使用通配符表示任意包，但是有几个包就要写几个<code>*.</code> 比如<code>* *.*.*.*.AccountServiceImpl.saveAccount()</code></p></li><li><p>包名可以使用..表示当前包及其子包 <code>* *..AccountServiceImpl.saveAccount()</code></p></li><li><p>类名和方法名均可以使用<code>*</code>实现通配</p></li><li><p>参数列表写数据类型或全限定类名</p></li><li><p>可以使用通配符表示任意参数类型，但必须有参数。也可以使用<code>..</code>表示有无参数均可以<br>全通配写法：<code>* *..*.*(..)</code></p></li><li><p>实际开发的通常写法是切到业务层实现类的所有方法<code>* com.billychen.service.impl.*.*(..)</code></p></li></ul></li></ol><p>以下是一个实例：</p><p>在该实例中，<code>Logger</code>是一个通知类，<code>AccountServiceImpl</code>是一个核心业务的类。</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta"><?xml version="1.0" encoding="UTF-8"?></span></span><br><span class="line"><span class="tag"><<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xmlns:aop</span>=<span class="string">"http://www.springframework.org/schema/aop"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="tag"><span class="string"> https://www.springframework.org/schema/beans/spring-beans.xsd</span></span></span><br><span class="line"><span class="tag"><span class="string"> http://www.springframework.org/schema/aop</span></span></span><br><span class="line"><span class="tag"><span class="string"> https://www.springframework.org/schema/aop/spring-aop.xsd"</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="comment"><!--配置service对象--></span></span><br><span class="line"> <span class="tag"><<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"accountService"</span> <span class="attr">class</span>=<span class="string">"com.billychen.service.impl.AccountServiceImpl"</span>></span></span><br><span class="line"> <span class="comment"><!-- instructs the container to proxy the surrounding bean --></span></span><br><span class="line"> <span class="tag"><<span class="name">aop:scoped-proxy</span>/></span></span><br><span class="line"> <span class="tag"></<span class="name">bean</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="comment"><!--配置Logger对象--></span></span><br><span class="line"> <span class="tag"><<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"logger"</span> <span class="attr">class</span>=<span class="string">"com.billychen.utils.Logger"</span>></span><span class="tag"></<span class="name">bean</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="comment"><!--配置AOP--></span></span><br><span class="line"> <span class="tag"><<span class="name">aop:config</span>></span></span><br><span class="line"> <span class="comment"><!--配置切面--></span></span><br><span class="line"> <span class="tag"><<span class="name">aop:aspect</span> <span class="attr">id</span>=<span class="string">"logAdvice"</span> <span class="attr">ref</span>=<span class="string">"logger"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">aop:before</span> <span class="attr">method</span>=<span class="string">"beforePrintLog"</span> <span class="attr">pointcut-ref</span>=<span class="string">"ptl"</span>></span><span class="tag"></<span class="name">aop:before</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">aop:after-returning</span> <span class="attr">method</span>=<span class="string">"afterReturningPrintLog"</span> <span class="attr">pointcut-ref</span>=<span class="string">"ptl"</span>></span><span class="tag"></<span class="name">aop:after-returning</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">aop:after-throwing</span> <span class="attr">method</span>=<span class="string">"afterThrowingPrintLog"</span> <span class="attr">pointcut-ref</span>=<span class="string">"ptl"</span>></span><span class="tag"></<span class="name">aop:after-throwing</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">aop:after</span> <span class="attr">method</span>=<span class="string">"afterPrintLog"</span> <span class="attr">pointcut-ref</span>=<span class="string">"ptl"</span>></span><span class="tag"></<span class="name">aop:after</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="comment"><!--仅限当前切面使用</span></span><br><span class="line"><span class="comment"> 如果写在切面之外，则可以供所有切面使用（要写在切面定义之前）--></span></span><br><span class="line"> <span class="tag"><<span class="name">aop:pointcut</span> <span class="attr">id</span>=<span class="string">"ptl"</span> <span class="attr">expression</span>=<span class="string">"execution(* com.billychen.service.impl.*.*(..))"</span>></span><span class="tag"></<span class="name">aop:pointcut</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">aop:aspect</span>></span></span><br><span class="line"> <span class="tag"></<span class="name">aop:config</span>></span></span><br><span class="line"></span><br><span class="line"><span class="tag"></<span class="name">beans</span>></span></span><br></pre></td></tr></table></figure><h2 id="3-使用注解"><a href="#3-使用注解" class="headerlink" title="3.使用注解"></a>3.使用注解</h2><p>配置类如下：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.billychen.config;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.context.annotation.ComponentScan;</span><br><span class="line"><span class="keyword">import</span> org.springframework.context.annotation.Configuration;</span><br><span class="line"><span class="keyword">import</span> org.springframework.context.annotation.EnableAspectJAutoProxy;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 配置类</span></span><br><span class="line"><span class="comment"> * 开启AOP注解</span></span><br><span class="line"><span class="comment"> * 指定创建IoC容器时需要扫描的包</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="meta">@EnableAspectJAutoProxy</span></span><br><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="meta">@ComponentScan</span>(basePackages = <span class="string">"com.billychen"</span>)</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">SpringConfig</span> </span>{</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p><code>Logger</code>类如下（即通知类）</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.billychen.utils;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.aspectj.lang.JoinPoint;</span><br><span class="line"><span class="keyword">import</span> org.aspectj.lang.ProceedingJoinPoint;</span><br><span class="line"><span class="keyword">import</span> org.aspectj.lang.annotation.*;</span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Component;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 模拟记录日志的工具类，提供了共用代码（通知）</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="meta">@Component</span></span><br><span class="line"><span class="meta">@Aspect</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Logger</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="comment">//指定切入点方法</span></span><br><span class="line"> <span class="meta">@Pointcut</span>(<span class="string">"execution(* com.billychen.service.impl.*.*(..))"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">ptl</span><span class="params">()</span> </span>{</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 前置</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="comment">//可以获取切点方法的参数</span></span><br><span class="line"> <span class="meta">@Before</span>(<span class="string">"ptl() && args(i)"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">beforePrintLog</span><span class="params">(JoinPoint joinPoint, <span class="keyword">int</span> i)</span> </span>{</span><br><span class="line"> Object[] args = joinPoint.getArgs();</span><br><span class="line"> System.out.println(<span class="string">"参数为"</span> + args[<span class="number">0</span>]);</span><br><span class="line"> System.out.println(<span class="string">"前置：Logger类中的BeforePrintLog方法开始记录日志！"</span>);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 后置</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="meta">@AfterReturning</span>(<span class="string">"ptl()"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">afterReturningPrintLog</span><span class="params">()</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"后置：Logger类中的AfterReturningPrintLog方法开始记录日志！"</span>);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 异常</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="meta">@AfterThrowing</span>(<span class="string">"ptl()"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">afterThrowingPrintLog</span><span class="params">()</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"异常：Logger类中的AfterThrowingPrintLog方法开始记录日志！"</span>);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 最终</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="meta">@After</span>(<span class="string">"ptl()"</span>)</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">afterPrintLog</span><span class="params">()</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"最终：Logger类中的AfterPrintLog方法开始记录日志！"</span>);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 环绕</span></span><br><span class="line"><span class="comment"> * ProceedingJoinPoint的方法proceed()可以明确调用切入点的方法</span></span><br><span class="line"><span class="comment"> * 环绕通知 是spring提供的一种可以在代码中手动控制增强方法何时执行的方式</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="comment">//@Around("ptl()")</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> Object <span class="title">aroundPrintLog</span><span class="params">(ProceedingJoinPoint joinPoint)</span> </span>{</span><br><span class="line"> <span class="comment">//明确调用业务层方法</span></span><br><span class="line"> Object returnValue = <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//得到方法执行的参数</span></span><br><span class="line"> Object[] args = joinPoint.getArgs();</span><br><span class="line"> System.out.println(<span class="string">"环绕通知——前置"</span>);</span><br><span class="line"> returnValue = joinPoint.proceed(args);</span><br><span class="line"> System.out.println(<span class="string">"环绕通知——后置"</span>);</span><br><span class="line"> <span class="keyword">return</span> returnValue;</span><br><span class="line"> } <span class="keyword">catch</span> (Throwable throwable) {</span><br><span class="line"> System.out.println(<span class="string">"环绕通知——异常"</span>);</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> RuntimeException(throwable);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> System.out.println(<span class="string">"环绕通知——最终"</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<categories>
<category> Spring </category>
</categories>
<tags>
<tag> Spring </tag>
<tag> Java </tag>
</tags>
</entry>
<entry>
<title>Spring——IoC容器</title>
<link href="/2020/09/10/spring-ioc/"/>
<url>/2020/09/10/spring-ioc/</url>
<content type="html"><![CDATA[<h1 id="Spring-IoC容器"><a href="#Spring-IoC容器" class="headerlink" title="Spring IoC容器"></a>Spring IoC容器</h1><h2 id="1-思想"><a href="#1-思想" class="headerlink" title="1.思想"></a>1.思想</h2><p><code>bean</code>对象的创建、依赖关系交给<code>Ioc</code>容器来管理，无需手动<code>new</code>对象，方便解耦，便于开发。</p><h2 id="2-IoC容器"><a href="#2-IoC容器" class="headerlink" title="2.IoC容器"></a>2.IoC容器</h2><p><code>Spring</code>容器的最顶层接口是<code>BeanFactory</code>，实际开发中常用<code>ApplicationContext</code>。</p><p>两个接口的区别：</p><ul><li><code>ApplicationContext</code>：立即加载。读取配置文件后马上创建对象放入容器。</li><li><code>BeanFactory</code>：延迟加载。什么时候根据<code>id</code>获取对象，什么时候才真正创建对象。</li></ul><p><code>ApplicationContext</code>的三个常用实现类</p><ul><li><p><code>ClassPathApplicationContext</code>：加载类路径下的配置文件。</p></li><li><p><code>FileSystemXmlApplicationContext</code>：加载磁盘任意路径下的配置文件。</p></li><li><p><code>AnnotationConfigApplicationContext</code>：读取注解 创建容器。</p></li></ul><h2 id="3-Bean"><a href="#3-Bean" class="headerlink" title="3.Bean"></a>3.Bean</h2><h3 id="1-创建bean的三种方式"><a href="#1-创建bean的三种方式" class="headerlink" title="1.创建bean的三种方式"></a>1.创建bean的三种方式</h3><ol><li>使用默认的无参构造器（如果没有无参构造器，则报错）</li><li>使用静态工厂的静态方法创建对象</li><li>使用实例工厂的方法创建对象</li></ol><a id="more"></a><h3 id="2-bean对象的生命周期"><a href="#2-bean对象的生命周期" class="headerlink" title="2.bean对象的生命周期"></a>2.bean对象的生命周期</h3><ol><li>单例<ul><li>出生：当容器创建时对象出生</li><li>活着：只要容器还在，对象一直活着</li><li>死亡：容器销毁，对象消亡</li><li>总结：单例对象的生命周期与容器相同</li></ul></li><li>多例<ul><li>出生：使用对象时才创建（延迟加载）</li><li>活着：对象只要在使用过程中就一直活着</li><li>死亡：当对象长时间不用且无其他对象引用时，由<code>GC</code>回收</li></ul></li></ol><h3 id="3-依赖注入"><a href="#3-依赖注入" class="headerlink" title="3.依赖注入"></a>3.依赖注入</h3><p> 依赖关系的管理交给Spring来维护在当前类需要用到其他类的对象时，由Spring为我们提供，只需在配置文件中说明。</p><p>依赖注入的数据有三类：</p><ol><li>基本类型和<code>String</code></li><li>其他<code>bean</code>类型（在配置文件中或注解中配置过的bean）</li><li>复杂类型（集合类型）</li></ol><p>注入的方式有三种：</p><ol><li>使用构造方法</li><li>使用<code>set</code>方法</li><li>使用注解</li></ol><h3 id="4-常用注解"><a href="#4-常用注解" class="headerlink" title="4.常用注解"></a>4.常用注解</h3><ol><li>用于创建对象的注解（作用类似于<code>bean</code>标签）</li></ol><ul><li><code>@Component</code></li></ul><blockquote><p><strong>作用</strong>：写在类之前，把当前类的对象注入到容器中</p><p><strong>属性</strong>：value 指定bean的id 默认值是当前类名首字母改为小写</p></blockquote><ul><li><p><code>@Controller</code>：一般用在表现层</p></li><li><p><code>@Serive</code>：一般用在业务层</p></li><li><p><code>@Repository</code>：一般用在持久层</p><p> 以上三个注解的作用与属性和<code>Component</code>一样，<br>他们三个是<code>Spring</code>框架提供的明确的三层使用的注解，使三层对象更加清晰。</p></li></ul><hr><ol start="2"><li>用于注入数据的注解（作用相当于<code>properties</code>标签）</li></ol><ul><li><p><code>@Autowired</code>:</p><blockquote><p><strong>作用</strong>：自动按照类型注入。只要容器中有唯一的一个bean对象类型和要注入的变量类型匹配，就可以注入成功</p><p><strong>使用的位置</strong>：变量上或方法上</p><p><strong>注意</strong>：如果容器中没有任何bean的类型匹配，则报错。<br>如果容器中有多个<code>bean</code>的类型和要注入的变量类型匹配，如果要注入的变量名称和<code>bean</code>的<code>id</code>相匹配，则注入之，否则报错。<br>另外，使用注解的方法注入时，set方法不是必须的</p></blockquote></li><li><p><code>@Qualifier</code></p><blockquote><p><strong>作用</strong>：在按照类中注入的基础上再按名称注入。</p><p><strong>注意</strong>：它给类成员注入时不能单独使用，必须和<code>Autowired</code>配合使用，但是在给方法参数注入时可以单独使用。</p><p><strong>属性</strong>：<code>value</code> 用于指定注入<code>bean</code>的<code>id</code></p></blockquote></li><li><p><code>@Resource</code></p><blockquote><p><strong>作用</strong>：直接按照<code>bean</code>的id注入，可以独立使用，不需要再和<code>Autowired</code>一起使用</p><p><strong>属性</strong>：name 用于指定注入<code>bean</code>的<code>id</code></p><p><strong>注意</strong>：以上三个注解只能注入其他<code>bean</code>类型的数据，而基本类型和<code>String</code>类型无法使用上述注解</p></blockquote></li></ul><p>另外，集合类型注入只能使用xml</p><ul><li><code>@Value</code><blockquote><p><strong>作用</strong>：用于注入基本类型和<code>String</code>类型的数据</p><p><strong>属性</strong>：<code>value</code>：用于指定数据的值</p><p>它可以使用<code>Spring</code>中的<code>SpEL</code>。<code>SpEL</code>写法：<code>${表达式}</code></p></blockquote></li></ul><hr><ol start="3"><li>一些和配置有关的注解</li></ol><ul><li><p>可以使用配置类以代替<code>bean.xml</code>配置文件的作用</p></li><li><p><code>@Configuration</code></p><blockquote><p><strong>作用</strong>：指定当前类是一个配置类</p><p><strong>细节</strong>：当配置类作为<code>AnnotationConfigApplicationContext</code>对象创建的参数时，可以不写。</p></blockquote></li><li><p><code>@ComponentScan</code></p><blockquote><p><strong>作用</strong>：指定创建容器时要扫描的包</p></blockquote></li><li><p><code>@Bean</code></p><blockquote><p><strong>作用</strong>：用在方法前，将方法的返回值作为<code>bean</code>对象存入<code>IoC</code>容器</p><p><strong>属性</strong>：<code>name</code> 用于指定<code>bean</code>的<code>id</code> 默认值为当前方法名</p><p><strong>细节</strong>：使用注解配置方法时，如果方法有参数，<code>Spring</code>框架会去容器中查找是否有该类型的<code>bean</code>，查找方式和<code>Autowired</code>相同</p></blockquote></li><li><p><code>@Import</code></p><blockquote><p><strong>作用</strong>：用于导入其他配置类</p><p><strong>属性</strong>：<code>value</code> 用于指定其他配置类的字节码</p></blockquote></li><li><p><code>@PropertySource</code></p><blockquote><p><strong>作用</strong>：用于指定properties文件的位置</p><p><strong>属性</strong>：<code>value</code> 指定文件名称和路径<br>关键字<code>classpath</code>表示类路径下</p></blockquote></li></ul>]]></content>
<categories>
<category> Spring </category>
</categories>
<tags>
<tag> Spring </tag>
<tag> Java </tag>
</tags>
</entry>
<entry>
<title>Git学习</title>
<link href="/2020/01/30/learngit/"/>
<url>/2020/01/30/learngit/</url>
<content type="html"><![CDATA[<h2 id="基本结构"><a href="#基本结构" class="headerlink" title="基本结构"></a>基本结构</h2><p>Git是一个分布式版本控制系统，分为工作区，版本库和远程仓库。</p><p>工作区是本地能看到的目录，版本库可分为暂存区和本地仓库，远程仓库被置于远程，可由Github托管。</p><p>把本地文件放入本地仓库分两步进行：</p><p>第一步：<code>git add</code>将工作区的文件添加到暂存区；</p><p>第二步：<code>git commit</code>将暂存区的所有内容提交到本地仓库（当前分支）</p><p>接下来，在本地仓库和远程仓库已经关联的条件下，即可使用<code>git push</code>推送当前分支到远程。</p><a id="more"></a><hr><h2 id="多人协作开发"><a href="#多人协作开发" class="headerlink" title="多人协作开发"></a>多人协作开发</h2><p><code>master</code>分支是主分支，用于发布版本；</p><p><code>dev</code>分支是开发分支。每个成员都在各自<code>dev</code>分支上开发，并时不时地推送到远程；</p><p><code>feature</code>分支可用于开发新功能，开发完成后，合并到<code>dev</code>分支，最后删除<code>dev</code>分支；</p><p><code>bug</code>分支可以被临时建立来修改bug，修改后，合并分支，删除<code>bug</code>分支。</p><p>总之，<code>master</code>分支用于发布版本，每个人在各自的<code>dev</code>分支上开发，时不时往远程的<code>dev</code>进行提交，合并。如果向远程提交<code>dev</code>分支时出现冲突（即你的同伴和你对同一份文件进行了修改），则需要先<code>git pull</code>，在本地解决冲突后再提交(<code>git commit</code>、<code>git push</code>)</p><hr><h2 id="常用命令"><a href="#常用命令" class="headerlink" title="常用命令"></a>常用命令</h2><ul><li><p>将指定文件添加进入暂存区</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git add <filename></span><br></pre></td></tr></table></figure><p>（<code>git add .</code>表示将所有文件加入暂存区）</p></li><li><p>删除版本库中暂存区指定文件</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git rm <filename></span><br></pre></td></tr></table></figure></li></ul><ul><li><p>将暂存区的修改提交到本地仓库</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git commit -m <span class="string">"your change"</span></span><br></pre></td></tr></table></figure></li><li><p>本地仓库与远程仓库建立联系（确保SSH Key已经配置好）</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git remote add origin https://github.com/YOUR_NAME/REPO_NAME.git</span><br></pre></td></tr></table></figure></li><li><p>将远程分支拉到工作区（出现冲突时需要进行这一步，因为要在本地进行合并）</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git pull</span><br></pre></td></tr></table></figure></li><li><p>提交到远程仓库</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git push origin <branch></span><br></pre></td></tr></table></figure><p>如果远程仓库为空，则</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git push -u origin <branch></span><br></pre></td></tr></table></figure></li><li><p>从远程仓库克隆（会自动把本地仓库与远程仓库关联起来）</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git <span class="built_in">clone</span> https://github.com/YOUR_NAME/REPO_NAME.git</span><br></pre></td></tr></table></figure></li><li><p>创建并进入分支</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git checkout -b <branch></span><br></pre></td></tr></table></figure><p>或者</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git switch -c <branch></span><br></pre></td></tr></table></figure></li><li><p>切换分支</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git switch <branch></span><br></pre></td></tr></table></figure></li><li><p>将目标分支合并到当前分支</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git merge <branch></span><br></pre></td></tr></table></figure></li><li><p>删除分支</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git branch -d <branch></span><br></pre></td></tr></table></figure></li><li><p>查看分支情况</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git <span class="built_in">log</span> --pretty=oneline --graph</span><br></pre></td></tr></table></figure></li><li><p>查看以往提交的版本</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git reflog</span><br></pre></td></tr></table></figure></li><li><p>版本回退<br>回退指定次数</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git reset --hard HEAD~<<span class="built_in">times</span>></span><br></pre></td></tr></table></figure><p>回退指定commit_id的版本（id可在log或reflog中找到）</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git reset --hard <commit_id></span><br></pre></td></tr></table></figure></li><li><p>改乱了工作区内的内容，想丢弃工作区的修改（返回到版本库的状态）</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git checkout -- <filename></span><br></pre></td></tr></table></figure></li><li><p>改乱了工作区的内容并且提交到暂存区，以下命令可将修改回退到工作区，此时就回到了上一个场景的情况</p><pre><code class="bash">git reset HEAD <filename></code></pre></li></ul>]]></content>
<categories>
<category> Git </category>
</categories>
<tags>
<tag> Git </tag>
</tags>
</entry>
<entry>
<title>Win10 + Ubuntu 16.04 双系统安装步骤以及问题的解决</title>
<link href="/2020/01/19/windows-ubuntu/"/>
<url>/2020/01/19/windows-ubuntu/</url>
<content type="html"><![CDATA[<h1 id="Win10-Ubuntu-16-04-双系统安装步骤以及问题的解决"><a href="#Win10-Ubuntu-16-04-双系统安装步骤以及问题的解决" class="headerlink" title="Win10 + Ubuntu 16.04 双系统安装步骤以及问题的解决"></a>Win10 + Ubuntu 16.04 双系统安装步骤以及问题的解决</h1><h2 id="双系统安装步骤"><a href="#双系统安装步骤" class="headerlink" title="双系统安装步骤"></a>双系统安装步骤</h2><h3 id="步骤一：Ubuntu-16-04系统盘的制作"><a href="#步骤一：Ubuntu-16-04系统盘的制作" class="headerlink" title="步骤一：Ubuntu 16.04系统盘的制作"></a>步骤一：Ubuntu 16.04系统盘的制作</h3><ol><li>下载Ubuntu镜像<br> 推荐使用<a href="https://mirrors.tuna.tsinghua.edu.cn/ubuntu-releases/16.04/" target="_blank" rel="noopener">清华大学开源软件镜像站</a>,选择ubuntu-16.04.6-desktop-amd64.iso下载即可</li><li>下载UltraSO，使用U盘制作启动盘<ol><li>选择<em>文件->打开</em>，打开Ubuntu的iso镜像。</li><li>在左下角区域选择U盘，点击<em>启动->写入硬盘映像</em>。</li><li>在弹出的对话框中选择写入方式为hdd或hdd+，对硬盘格式化后再点击写入。</li><li>写入完毕后启动盘制作完成。</li></ol></li></ol><h3 id="步骤二：分区与安装"><a href="#步骤二：分区与安装" class="headerlink" title="步骤二：分区与安装"></a>步骤二：分区与安装</h3><ol><li>使用Windows磁盘管理进行分区。<br> 通过<em>WIN + X</em>进入磁盘管理，右键点击有空余空间的磁盘，选择<em>压缩卷</em>，一般大小可设置为50G。此后的Ubuntu系统便安装在此区域。</li><li>关闭Win10系统的快速启动和安全启动。<br> 具体操作可参考<a href="https://www.jianshu.com/p/38e6be8efecf" target="_blank" rel="noopener">win10安装ubuntu18.04 LTS双系统</a></li><li>将启动盘插入电脑，重启电脑，进入BIOS，将U盘设置为第一启动项。</li><li>按照提示信息进行安装。<ul><li><strong>注意</strong>：在分区时，选择自定义模式。一般来说，只需要划分两个区，即swap区(充当虚拟内存，分区格式为swap)和主分区(挂载点/，安装系统和软件，分区格式为ext4)</li></ul></li><li>安装完成后，拔下U盘，重启电脑，选择进入Ubuntu系统。至此，双系统安装已经完成。</li></ol><a id="more"></a><hr><h2 id="遇到的问题以及解决方案"><a href="#遇到的问题以及解决方案" class="headerlink" title="遇到的问题以及解决方案"></a>遇到的问题以及解决方案</h2><h3 id="双系统安装在logo界面卡死"><a href="#双系统安装在logo界面卡死" class="headerlink" title="双系统安装在logo界面卡死"></a>双系统安装在logo界面卡死</h3><p><strong>解决方案：</strong> 问题的原因可能是Ubuntu系统对双显卡支持不友好，可以在安装过程中选中install ubuntu选项，按e键进入编辑</p><p>将<code>quite splash ---</code>改为<code>quite splash nomodeset</code></p><p>显卡被禁止后默认分辨率为800x600，所以窗口可能显示不全，此时只需要按住<em>alt + s</em>（或者<em>alt + F7</em>）拖动窗口即可。</p><p>重启电脑后，进入Ubuntu系统仍需要进行上述修改。</p><p>进入Ubuntu系统后，如果无线网络连接正常（如果无法连接无线网，则需要接网线使用有线网），可以在<em>系统设置->软件和更新->附加驱动</em>中找到NVDIA相关选项，选择<em>应用更改</em>后重新启动即可解决显卡问题。</p><h3 id="无线网卡问题"><a href="#无线网卡问题" class="headerlink" title="无线网卡问题"></a>无线网卡问题</h3><p> 进入Ubuntu系统后，可能无法找到无线网络。原因可能是系统对硬件支持不友好，无法直接找到无线网卡驱动。</p><p> <strong>解决方案：</strong> 网络上最常用的解决方法是在终端输入以下命令（当然需要确保有线网络已连接）：</p> <figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">$ sudo apt-get update</span><br><span class="line">$ sudo apt-get install bcmwl-kernal-source</span><br></pre></td></tr></table></figure><p> 如果问题仍然无法解决，那么就需要手动下载对应你的无线网卡型号的驱动软件。</p><p> 以我为例，我的网卡型号为rtl8821ce。</p><ol><li><p>下载网卡驱动。</p> <figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ git <span class="built_in">clone</span> https://github.com/endlessm/linux/tree/master/drivers/net/wireless/rtl8821ce</span><br></pre></td></tr></table></figure></li><li><p>修改Makefile文件<br> 将<code>export TopDIR ?=</code>之后的内容改为当前目录地址，例如：</p> <figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">export TopDIR ?= /home/chenqiming/rtl8821ce/</span><br></pre></td></tr></table></figure></li><li><p>在当前目录下打开终端，进行：</p> <figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">$ make</span><br><span class="line">$ sudo make install</span><br><span class="line">$ sudo modprobe -a 8821ce</span><br></pre></td></tr></table></figure><p>至此，驱动已经安装完成，重新启动后即可寻找到无线wifi。</p></li></ol>]]></content>
<categories>
<category> Linux </category>
</categories>
<tags>
<tag> Linux </tag>
<tag> Windows </tag>
<tag> Ubuntu </tag>
</tags>
</entry>
</search>