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<a class="post-title-link" href="/2016/05/18/effetive-ruby-tldr-part2/" itemprop="url">
effetive-ruby-tldr-part2
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<h2 id="11-Create-namespace-by-nesting-code-in-Module"><a href="#11-Create-namespace-by-nesting-code-in-Module" class="headerlink" title="#11. Create namespace by nesting code in Module"></a>#11. Create namespace by nesting code in Module</h2><ul>
<li>Use modules to create namespece by nesting definiton inside them.</li>
<li>Mirror you namesapece structure to your dir structure.</li>
<li>Use <code>::</code> to fully qualify a top-level constant.</li>
</ul>
<h2 id="12-Understand-the-Different-Flavors-of-Equality"><a href="#12-Understand-the-Different-Flavors-of-Equality" class="headerlink" title="#12. Understand the Different Flavors of Equality"></a>#12. Understand the Different Flavors of Equality</h2><ul>
<li>Use <code>==</code> to test if two obejcts represent the same value.</li>
</ul>
<figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1</span> == <span class="string">`1.0`</span> <span class="comment"># true</span></span><br></pre></td></tr></table></figure>
<ul>
<li>Use <code>eql?</code> to test if two objects represent the same value and also the same<br>type.</li>
</ul>
<figure class="highlight ruby"><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"><span class="number">1</span> == <span class="string">`1.0`</span> <span class="comment"># false</span></span><br><span class="line"><span class="number">1</span> == <span class="number">1</span> <span class="comment"># true</span></span><br></pre></td></tr></table></figure>
<ul>
<li><p>Use <code>equal?</code> to test if two objects are the same object (with same object_id),<br>so <strong>never</strong> override this method.</p>
</li>
<li><p><code>===</code> - <code>== || =~ || is_a?</code></p>
</li>
</ul>
<figure class="highlight ruby"><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="string">'a'</span>===<span class="string">'a'</span> <span class="comment">#true - 'a'=='a'</span></span><br><span class="line">/a/i===<span class="string">'Abc'</span> <span class="comment">#0 - /a/i =~ 'Abc'</span></span><br><span class="line"><span class="constant">String</span>===<span class="string">'a'</span> <span class="comment">#true - 'a'.is_a? String</span></span><br></pre></td></tr></table></figure>
<h2 id="13-Implement-Comparison-via-lt-gt-and-the-Comparable-Module"><a href="#13-Implement-Comparison-via-lt-gt-and-the-Comparable-Module" class="headerlink" title="#13. Implement Comparison via <=> and the Comparable Module"></a>#13. Implement Comparison via <=> and the Comparable Module</h2><ul>
<li>Implement object ordering by defining a “<=>” operator and including the Comparable module.</li>
<li>The “<=>” operator should return nil if the left operand can’t be compared with the right.</li>
<li>If you implement “<=>” for a class you should consider aliasing eql? to “==”, especially if you want instances to be usable as hash keys. In which case you should also override the hash method. NOTE. <code>==</code> does <strong>NOT</strong> test type equity.</li>
</ul>
<h2 id="14-Share-Private-State-Through-Protected-Methods"><a href="#14-Share-Private-State-Through-Protected-Methods" class="headerlink" title="#14. Share Private State Through Protected Methods"></a>#14. Share Private State Through Protected Methods</h2><ul>
<li>Protected methods can be called with an explicit receiver from objects of the same class</li>
</ul>
<h2 id="15-Prefer-Class-Instance-Variables-to-Class-Variables"><a href="#15-Prefer-Class-Instance-Variables-to-Class-Variables" class="headerlink" title="#15. Prefer Class Instance Variables to Class Variables"></a>#15. Prefer Class Instance Variables to Class Variables</h2><h2 id="16-Duplicate-Collections-Passed-as-Arguments-Before-Mutating-Them"><a href="#16-Duplicate-Collections-Passed-as-Arguments-Before-Mutating-Them" class="headerlink" title="#16. Duplicate Collections Passed as Arguments Before Mutating Them"></a>#16. Duplicate Collections Passed as Arguments Before Mutating Them</h2><ul>
<li>Method arguments in Ruby are passed as references, not values</li>
<li>The dup and clone methods only create shallow copies.</li>
</ul>
<figure class="highlight ruby"><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></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">User</span></span></span><br><span class="line"> <span class="keyword">attr_accessor</span> <span class="symbol">:name</span></span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">def</span> <span class="title">initialize</span><span class="params">(name)</span></span></span><br><span class="line"> <span class="variable">@name</span> = name</span><br><span class="line"> <span class="keyword">end</span></span><br><span class="line"><span class="keyword">end</span></span><br><span class="line"></span><br><span class="line">u1 = <span class="constant">User</span>.new <span class="string">'kevin'</span></span><br><span class="line">u2 = <span class="constant">Use</span>.new <span class="string">'others'</span></span><br><span class="line"></span><br><span class="line">arr = [u1, u2]</span><br><span class="line">arr2 = arr.dup</span><br><span class="line"></span><br><span class="line">u2.name = <span class="string">'new name'</span></span><br><span class="line"></span><br><span class="line">arr == arr2 <span class="comment"># true</span></span><br></pre></td></tr></table></figure>
<ul>
<li>For most objects, Marshal can be used to create deep copies when needed.</li>
</ul>
<figure class="highlight ruby"><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">arr3 = <span class="constant">Marshal</span>.load <span class="constant">Marshal</span>.dump arr</span><br><span class="line"></span><br><span class="line">u2.name = <span class="string">'new new'</span></span><br><span class="line"></span><br><span class="line">arr == arr3 <span class="comment">#false</span></span><br></pre></td></tr></table></figure>
<h2 id="17-Use-the-Array-Method-to-Convert-nil-and-Scalar-Objects-into-Arrays"><a href="#17-Use-the-Array-Method-to-Convert-nil-and-Scalar-Objects-into-Arrays" class="headerlink" title="#17. Use the Array Method to Convert nil and Scalar Objects into Arrays"></a>#17. Use the Array Method to Convert nil and Scalar Objects into Arrays</h2><figure class="highlight ruby"><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="constant">Array</span>(<span class="keyword">nil</span>) <span class="comment"># []</span></span><br><span class="line"><span class="constant">Array</span>([<span class="keyword">nil</span>, <span class="symbol">:a</span>]) <span class="comment"># [nil, :a]</span></span><br><span class="line"><span class="constant">Array</span>({<span class="symbol">a:</span><span class="number">12</span>,<span class="symbol">b:</span><span class="number">323</span>} <span class="comment">#[:a, :b]</span></span><br><span class="line"></span><br><span class="line"><span class="comment"># Array() - First tries to call Array#to_ary on arg, then Array#to_a.</span></span><br></pre></td></tr></table></figure>
<h2 id="18-Consider-Set-for-Efficient-Element-Inclusion-Checking"><a href="#18-Consider-Set-for-Efficient-Element-Inclusion-Checking" class="headerlink" title="#18. Consider Set for Efficient Element Inclusion Checking"></a>#18. Consider Set for Efficient Element Inclusion Checking</h2><ul>
<li><code>require 'set'</code> before you use it.</li>
</ul>
<h2 id="19-Know-How-to-Fold-Collections-with-reduce"><a href="#19-Know-How-to-Fold-Collections-with-reduce" class="headerlink" title="#19. Know How to Fold Collections with reduce"></a>#19. Know How to Fold Collections with reduce</h2><ul>
<li>Always use a starting value for the accumulator.</li>
</ul>
<figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">[<span class="number">1</span>,<span class="number">2</span>,<span class="number">3</span>].reduce(<span class="number">0</span>,<span class="symbol">:+</span>) <span class="comment">#6</span></span><br></pre></td></tr></table></figure>
<ul>
<li>The block given to reduce should always return an accumulator. It’s fine to mutate the current accumulator, just remember to return it from the block”.</li>
</ul>
<figure class="highlight ruby"><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="number">1</span>,<span class="number">2</span>,<span class="number">3</span>].reduce({}) <span class="keyword">do</span> |map, e|</span><br><span class="line"> map[e.to_s] = e</span><br><span class="line"> map</span><br><span class="line"><span class="keyword">end</span></span><br></pre></td></tr></table></figure>
<h2 id="20-Consider-Using-a-Default-Hash-Value"><a href="#20-Consider-Using-a-Default-Hash-Value" class="headerlink" title="#20. Consider Using a Default Hash Value"></a>#20. Consider Using a Default Hash Value</h2><h2 id="21-Prefer-Delegation-to-Inheriting-from-Collection-Classes"><a href="#21-Prefer-Delegation-to-Inheriting-from-Collection-Classes" class="headerlink" title="#21. Prefer Delegation to Inheriting from Collection Classes"></a>#21. Prefer Delegation to Inheriting from Collection Classes</h2>
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<a class="post-title-link" href="/2016/05/12/effetive-ruby-tldr-part1/" itemprop="url">
Effetive Ruby TLDR - part1
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2016-05-12
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<h2 id="“Accustoming-Yourself-to-Ruby”"><a href="#“Accustoming-Yourself-to-Ruby”" class="headerlink" title="“Accustoming Yourself to Ruby”"></a>“Accustoming Yourself to Ruby”</h2><h3 id="1-Understand-What-Ruby-Considers-To-Be-True"><a href="#1-Understand-What-Ruby-Considers-To-Be-True" class="headerlink" title="#1. Understand What Ruby Considers To Be True"></a>#1. Understand What Ruby Considers To Be True</h3><ul>
<li>Every value is <code>true</code>expect <code>false</code> and <code>nil</code>.</li>
<li>The number <code>0</code> is <code>ture</code> in Ruby.</li>
<li>Check if a value is nil with <code>value#nil?</code>.</li>
</ul>
<h3 id="2-Treat-All-Objects-As-If-They-Could-Be-nil"><a href="#2-Treat-All-Objects-As-If-They-Could-Be-nil" class="headerlink" title="#2. Treat All Objects As If They Could Be nil"></a>#2. Treat All Objects As If They Could Be nil</h3><ul>
<li>Only <code>nil.nil?</code> returns <code>true</code>.</li>
<li>You can cast a nil to a empty string with <code>nil.to_s</code> or to a int with<br><code>nil.to_i</code>.</li>
</ul>
<h3 id="3-Avoid-Ruby’s-Cryptic-Perlisms"><a href="#3-Avoid-Ruby’s-Cryptic-Perlisms" class="headerlink" title="#3. Avoid Ruby’s Cryptic Perlisms"></a>#3. Avoid Ruby’s Cryptic Perlisms</h3><ul>
<li>Prefer <code>String#match</code> to <code>str =~</code>.</li>
<li>Don’t modify global variables unless you must do.</li>
</ul>
<h3 id="4-Be-Aware-That-Constants-Are-Mutable"><a href="#4-Be-Aware-That-Constants-Are-Mutable" class="headerlink" title="#4. Be Aware That Constants Are Mutable"></a>#4. Be Aware That Constants Are Mutable</h3><ul>
<li>Always <code>freeze</code> constant values to prevent them to be mutated.</li>
<li>To prevent assigning new values to existing constants, freeze the module they<br>are defined in.</li>
</ul>
<h3 id="5-Pay-attention-to-runtime-warnings"><a href="#5-Pay-attention-to-runtime-warnings" class="headerlink" title="#5. Pay attention to runtime warnings"></a>#5. Pay attention to runtime warnings</h3><ul>
<li>Use the <code>-w</code> CLI option to enable compile and runtime warnings. Or make it<br>part of the <code>RUBYOPT</code> env variable.</li>
</ul>
<h2 id="Classes-Objects-and-Modules"><a href="#Classes-Objects-and-Modules" class="headerlink" title="Classes, Objects and Modules"></a>Classes, Objects and Modules</h2><h3 id="6-Know-how-ruby-build-inheritance-hierarchies"><a href="#6-Know-how-ruby-build-inheritance-hierarchies" class="headerlink" title="#6. Know how ruby build inheritance hierarchies"></a>#6. Know how ruby build inheritance hierarchies</h3><ul>
<li>Method lookup algo - move right, then go up, that means when you clll a method<br><code>foo.bar</code>, you move to the right, find the class of the object <code>foo</code>, if you<br>find <code>bar</code> in <code>foo</code>‘s class, then invoke it, or move to <code>foo</code>‘s superclass, do<br>the same thing.</li>
<li>If no method has been found, <code>method_missing</code> will be called with the same<br>algo as above.</li>
<li>Module are classes too. Including modules silently creates singleton classes<br>which are inserted into the hierarchy above the including class.</li>
<li>Class methods are just instance methods of the class’s metaclass</li>
</ul>
<h3 id="7-Be-Aware-of-the-Different-Behaviors-of-super"><a href="#7-Be-Aware-of-the-Different-Behaviors-of-super" class="headerlink" title="#7. Be Aware of the Different Behaviors of super"></a>#7. Be Aware of the Different Behaviors of super</h3><ul>
<li>Use <code>super</code> to call the overridden method.</li>
<li>Use <code>super</code> with no args and no parentheses is equivalent to passing it all of<br>the arguments which were given to the enclosing method.</li>
<li>Use to <code>super()</code> to call overriden method withoug passing any arguments.</li>
</ul>
<h3 id="8-Invoke-super-When-Initializing-Sub-classes"><a href="#8-Invoke-super-When-Initializing-Sub-classes" class="headerlink" title="#8. Invoke super When Initializing Sub-classes"></a>#8. Invoke super When Initializing Sub-classes</h3><ul>
<li>Ruby doesn’t automatically call the <code>initialize</code> method in the superclass when<br>creating objects from a subclass</li>
<li>Call the overriden <code>initialize</code> method explicitly with <code>super</code></li>
</ul>
<h3 id="9-Be-Alert-for-Ruby’s-Most-Vexing-Parse"><a href="#9-Be-Alert-for-Ruby’s-Most-Vexing-Parse" class="headerlink" title="#9. Be Alert for Ruby’s Most Vexing Parse"></a>#9. Be Alert for Ruby’s Most Vexing Parse</h3><ul>
<li>Setter method must have a reciever, inside the class that defines it, the<br>receiver should be <code>self</code></li>
<li>Avoid using <code>self</code> when call other methods inside a class.</li>
</ul>
<h3 id="10-Prefer-Struct-to-Hash-for-Structured-Data"><a href="#10-Prefer-Struct-to-Hash-for-Structured-Data" class="headerlink" title="#10. Prefer Struct to Hash for Structured Data"></a>#10. Prefer Struct to Hash for Structured Data</h3><ul>
<li>When dealing with structured data which doesn’t quite justify a new class<br>prefer using Struct to Hash.</li>
<li>Assign the return value of Struct::new to a constant and treat that constant<br>like a class.</li>
</ul>
<h4 id="Demo"><a href="#Demo" class="headerlink" title="Demo"></a>Demo</h4><figure class="highlight ruby"><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="constant">User</span> = <span class="constant">Struct</span>.new(<span class="symbol">:name</span>, <span class="symbol">:age</span>) <span class="comment"># User.class = Class</span></span><br><span class="line">user = <span class="constant">User</span>.new(<span class="string">'kevin'</span>, <span class="number">18</span>)</span><br><span class="line">puts user.name</span><br><span class="line">user.age = <span class="number">22</span></span><br></pre></td></tr></table></figure>
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<a class="post-title-link" href="/2016/04/13/hexo-plus-ghpages/" itemprop="url">
Hexo + Github Pages = 你的博客
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<h3 id="曾经的故事"><a href="#曾经的故事" class="headerlink" title="曾经的故事"></a>曾经的故事</h3><p>最近又想搞搞博客了，之前使用过 <code>Hexo</code>，印象不错，但是唯一有一个问题就是我当时是使用<code>hexo d</code>来把<code>hexo g</code>生成的<code>public</code>目录下的内容放到github 上的，后来因为换电脑等等原因，源文件已经找不到了。</p>
<h3 id="有时候也很笨"><a href="#有时候也很笨" class="headerlink" title="有时候也很笨"></a>有时候也很笨</h3><p>因此，觉得这个东西不好用，<code>hexo d</code>只是部署生成的表态文件到 github，而不会把源文件也放到 github，这样如果我换电脑或者使用其它电脑时就很不方便，我还得再建一个 repo 去维护这个东西，所以决定尝试一下<code>jekyll</code></p>
<h3 id="为什么放弃jekyll"><a href="#为什么放弃jekyll" class="headerlink" title="为什么放弃jekyll"></a>为什么放弃<code>jekyll</code></h3><p>首先我得说下我对静态博客工具的态度：</p>
<ul>
<li>不要很难上手，因为我不想在这上面花太多功夫</li>
<li>可以与github pages集成</li>
<li>支持主题，并且主题要很容易切换 （虽然博客的重点是内容而非表面，但是人都有爱美之心，并且容易喜新厌旧）</li>
</ul>
<p>我想<code>jekyll</code>与 github pages 是天然集成的，并且它还有无数非常美丽的主题，但是，它的主题切换就不像<code>hexo</code>那么的方便了，当然有可能是我没有搞清楚，但是， anyway，我不想在这上面花太多功夫，所以，决定回归<code>hexo</code>.</p>
<h3 id="如何重回-hexo"><a href="#如何重回-hexo" class="headerlink" title="如何重回 hexo"></a>如何重回 <code>hexo</code></h3><h4 id="versoin-control你的源代码"><a href="#versoin-control你的源代码" class="headerlink" title="versoin control你的源代码"></a>versoin control你的源代码</h4><p>对于上面我说的<code>hexo</code>的源代码如何保存的问题，我现在的做法是这样的<br>建立一个新的分支<code>blog/hexo</code>， 这里面就放着从<code>hexo init</code>到后面各种修改的内容，但是下面这几个文件我觉得是没有必要提交的，所以，可以把它们加到<code>.gitignore</code>文件中</p>
<figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">.deploy_git/ node_modules/ public/ themes/ db.json</span><br></pre></td></tr></table></figure>
<p>这里特别要注意的是<code>themes</code>，因为这下面放了你下载的主题，你是很有可能对这些主题进行自定义配置的，所以我的想法是创建一个相对应主题的配置文件，然后把<code>themes/bla-theme/bla.file</code> 链接到你新建的配置文件。（当然了，我还没来得及弄）</p>
<h4 id="部署你的网站"><a href="#部署你的网站" class="headerlink" title="部署你的网站"></a>部署你的网站</h4><p><code>hexo</code>提供了<code>hexo-deployer-git</code>可以让你只用一句命令<code>hexo d</code>就可以将你的网站部署到 github pages 上, 具体请看<a href="https://hexo.io/docs/deployment.html" target="_blank" rel="external">官方文档</a></p>
<p>在使用这个工具之前，你需要确保</p>
<ol>
<li><p>你已经配置了你的 git repo 信息到<code>_config.yml</code>中，示例如下：</p>
<figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">deploy: type: git repo: git@github.com:kevinjom/kevinjom.github.io.git branch: master</span><br></pre></td></tr></table></figure>
</li>
<li><p>先执行<code>hexo g</code></p>
</li>
</ol>
<p>当然了，如果嫌麻烦，你可以写一个简单的脚本。下面是一个例子</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><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="shebang">#!/bin/bash</span><br><span class="line"></span></span><br><span class="line"><span class="built_in">set</span> <span class="operator">-e</span></span><br><span class="line"></span><br><span class="line">PROG=$(basename <span class="variable">$0</span>)</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="title">usage</span></span>() {</span><br><span class="line"> <span class="built_in">echo</span> <span class="string">"<span class="variable">$PROG</span> <commit message>"</span></span><br><span class="line"> <span class="built_in">exit</span> <span class="number">1</span></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">[[ -n <span class="variable">$1</span> ]] || usage</span><br><span class="line"></span><br><span class="line">git stash</span><br><span class="line">git pull origin blog/hexo --rebase</span><br><span class="line">git stash pop || <span class="built_in">echo</span> <span class="string">"no stash to pop"</span></span><br><span class="line">git add .</span><br><span class="line">git commit -m <span class="string">"<span class="variable">$1</span>"</span></span><br><span class="line"></span><br><span class="line">hexo g</span><br><span class="line">hexo d</span><br></pre></td></tr></table></figure>
<h3 id="自定义域名过期了怎么办"><a href="#自定义域名过期了怎么办" class="headerlink" title="自定义域名过期了怎么办"></a>自定义域名过期了怎么办</h3><p>如果曾经配置过<code>CNAME</code>，但是域名过期了，又没有新域名使用，你想使用<code>bla.github.io</code>来访问，但你会发现 github还是会跳转至你曾经的域名，解决办法是将 <code>CNAME</code>的内容更新为<code>bla.github.io</code></p>
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Spring AOP 实现原理
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<h2 id="什么是AOP"><a href="#什么是AOP" class="headerlink" title="什么是AOP"></a>什么是AOP</h2><p>AOP（Aspect-OrientedProgramming，面向方面编程），可以说是OOP（Object-Oriented Programing，面向对象编程）的补充和完善。OOP引入封装、继承和多态性等概念来建立一种对象层次结构，用以模拟公共行为的一个集合。当我们需要为分散的对象引入公共行为的时候，OOP则显得无能为力。也就是说，OOP允许你定义从上到下的关系，但并不适合定义从左到右的关系。例如日志功能。日志代码往往水平地散布在所有对象层次中，而与它所散布到的对象的核心功能毫无关系。对于其他类型的代码，如安全性、异常处理和透明的持续性也是如此。这种散布在各处的无关的代码被称为横切（cross-cutting）代码，在OOP设计中，它导致了大量代码的重复，而不利于各个模块的重用。</p>
<p>而AOP技术则恰恰相反，它利用一种称为“横切”的技术，剖解开封装的对象内部，并将那些影响了多个类的公共行为封装到一个可重用模块，并将其名为“Aspect”，即方面。所谓“方面”，简单地说，就是将那些与业务无关，却为业务模块所共同调用的逻辑或责任封装起来，便于减少系统的重复代码，降低模块间的耦合度，并有利于未来的可操作性和可维护性。AOP代表的是一个横向的关系，如果说“对象”是一个空心的圆柱体，其中封装的是对象的属性和行为；那么面向方面编程的方法，就仿佛一把利刃，将这些空心圆柱体剖开，以获得其内部的消息。而剖开的切面，也就是所谓的“方面”了。然后它又以巧夺天功的妙手将这些剖开的切面复原，不留痕迹。</p>
<p>使用“横切”技术，AOP把软件系统分为两个部分：核心关注点和横切关注点。业务处理的主要流程是核心关注点，与之关系不大的部分是横切关注点。横切关注点的一个特点是，他们经常发生在核心关注点的多处，而各处都基本相似。比如权限认证、日志、事务处理。Aop 的作用在于分离系统中的各种关注点，将核心关注点和横切关注点分离开来。正如Avanade公司的高级方案构架师Adam Magee所说，AOP的核心思想就是“将应用程序中的商业逻辑同对其提供支持的通用服务进行分离。”</p>
<p>实现AOP的技术，主要分为两大类：一是采用动态代理技术，利用截取消息的方式，对该消息进行装饰，以取代原有对象行为的执行；二是采用静态织入的方式，引入特定的语法创建“方面”，从而使得编译器可以在编译期间织入有关“方面”的代码。</p>
<h2 id="AOP使用场景"><a href="#AOP使用场景" class="headerlink" title="AOP使用场景"></a>AOP使用场景</h2><p>AOP用来封装横切关注点，具体可以在下面的场景中使用:</p>
<ul>
<li>Authentication 权限</li>
<li>Caching 缓存</li>
<li>Context passing 内容传递</li>
<li>Error handling 错误处理</li>
<li>Lazy loading 懒加载</li>
<li>Debugging 调试</li>
<li>logging, tracing, profiling and monitoring 记录跟踪 优化 校准</li>
<li>Performance optimization 性能优化</li>
<li>Persistence 持久化</li>
<li>Resource pooling 资源池</li>
<li>Synchronization 同步</li>
<li>Transactions 事务</li>
</ul>
<h2 id="AOP相关概念"><a href="#AOP相关概念" class="headerlink" title="AOP相关概念"></a>AOP相关概念</h2><ul>
<li>方面（Aspect）：一个关注点的模块化，这个关注点实现可能另外横切多个对象。事务管理是J2EE应用中一个很好的横切关注点例子。方面用Spring的 Advisor或拦截器实现。</li>
<li>连接点（Joinpoint）: 程序执行过程中明确的点，如方法的调用或特定的异常被抛出。</li>
<li>通知（Advice）: 在特定的连接点，AOP框架执行的动作。各种类型的通知包括“around”、“before”和“throws”通知。通知类型将在下面讨论。许多AOP框架包括Spring都是以拦截器做通知模型，维护一个“围绕”连接点的拦截器链。Spring中定义了四个advice: BeforeAdvice, AfterAdvice, ThrowAdvice和DynamicIntroductionAdvice</li>
<li>切入点（Pointcut）: 指定一个通知将被引发的一系列连接点的集合。AOP框架必须允许开发者指定切入点：例如，使用正则表达式。 Spring定义了Pointcut接口，用来组合MethodMatcher和ClassFilter，可以通过名字很清楚的理解， MethodMatcher是用来检查目标类的方法是否可以被应用此通知，而ClassFilter是用来检查Pointcut是否应该应用到目标类上</li>
<li>引入（Introduction）: 添加方法或字段到被通知的类。 Spring允许引入新的接口到任何被通知的对象。例如，你可以使用一个引入使任何对象实现 IsModified接口，来简化缓存。Spring中要使用Introduction, 可有通过DelegatingIntroductionInterceptor来实现通知，通过DefaultIntroductionAdvisor来配置Advice和代理类要实现的接口</li>
<li>目标对象（Target Object）: 包含连接点的对象。也被称作被通知或被代理对象。POJO</li>
<li>AOP代理（AOP Proxy）: AOP框架创建的对象，包含通知。 在Spring中，AOP代理可以是JDK动态代理或者CGLIB代理。</li>
<li>织入（Weaving）: 组装方面来创建一个被通知对象。这可以在编译时完成（例如使用AspectJ编译器），也可以在运行时完成。Spring和其他纯Java AOP框架一样，在运行时完成织入。</li>
</ul>
<h2 id="Spring-AOP组件"><a href="#Spring-AOP组件" class="headerlink" title="Spring AOP组件"></a>Spring AOP组件</h2><p>下面这种类图列出了Spring中主要的AOP组件<br><img src="/images/spring-aop.jpg" alt=""></p>
<h2 id="如何使用Spring-AOP"><a href="#如何使用Spring-AOP" class="headerlink" title="如何使用Spring AOP"></a>如何使用Spring AOP</h2><p>可以通过配置文件或者编程的方式来使用Spring AOP。</p>
<p>配置可以通过xml文件来进行，大概有四种方式：</p>
<ol>
<li>配置ProxyFactoryBean，显式地设置advisors, advice, target等</li>
<li>配置AutoProxyCreator，这种方式下，还是如以前一样使用定义的bean，但是从容器中获得的其实已经是代理对象</li>
<li>通过<aop:config>来配置</aop:config></li>
<li>通过<aop: aspectj-autoproxy="">来配置，使用AspectJ的注解来标识通知及切入点</aop:></li>
</ol>
<p>也可以直接使用ProxyFactory来以编程的方式使用Spring AOP，通过ProxyFactory提供的方法可以设置target对象, advisor等相关配置，最终通过 getProxy()方法来获取代理对象</p>
<p>具体使用的示例可以google. 这里略去</p>
<h2 id="Spring-AOP代理对象的生成"><a href="#Spring-AOP代理对象的生成" class="headerlink" title="Spring AOP代理对象的生成"></a>Spring AOP代理对象的生成</h2><p>Spring提供了两种方式来生成代理对象: JDKProxy和Cglib，具体使用哪种方式生成由AopProxyFactory根据AdvisedSupport对象的配置来决定。默认的策略是如果目标类是接口，则使用JDK动态代理技术，否则使用Cglib来生成代理。下面我们来研究一下Spring如何使用JDK来生成代理对象，具体的生成代码放在JdkDynamicAopProxy这个类中，直接上相关代码：</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><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * <ol></span><br><span class="line"> * <li>获取代理类要实现的接口,除了Advised对象中配置的,还会加上SpringProxy, Advised(opaque=false)</span><br><span class="line"> * <li>检查上面得到的接口中有没有定义 equals或者hashcode的接口</span><br><span class="line"> * <li>调用Proxy.newProxyInstance创建代理对象</span><br><span class="line"> * </ol></span><br><span class="line"> */</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> Object <span class="title">getProxy</span><span class="params">(ClassLoader classLoader)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (logger.isDebugEnabled()) {</span><br><span class="line"> logger.debug(<span class="string">"Creating JDK dynamic proxy: target source is "</span> +<span class="keyword">this</span>.advised.getTargetSource());</span><br><span class="line"> }</span><br><span class="line"> Class[] proxiedInterfaces =AopProxyUtils.completeProxiedInterfaces(<span class="keyword">this</span>.advised);</span><br><span class="line"> findDefinedEqualsAndHashCodeMethods(proxiedInterfaces);</span><br><span class="line"> <span class="keyword">return</span> Proxy.newProxyInstance(classLoader, proxiedInterfaces, <span class="keyword">this</span>);</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>那这个其实很明了，注释上我也已经写清楚了，不再赘述。</p>
<p>下面的问题是，代理对象生成了，那切面是如何织入的？<br>我们知道<code>InvocationHandler</code>是JDK动态代理的核心，生成的代理对象的方法调用都会委托到<code>InvocationHandler.invoke()</code>方法。而通过<code>JdkDynamicAopProxy</code>的签名我们可以看到这个类其实也实现了<code>InvocationHandler</code>，下面我们就通过分析这个类中实现的<code>invoke()</code>方法来具体看下Spring AOP是如何织入切面的。</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></pre></td><td class="code"><pre><span class="line"><span class="function">publicObject <span class="title">invoke</span><span class="params">(Object proxy, Method method, Object[] args)</span> throwsThrowable </span>{</span><br><span class="line"> MethodInvocation invocation = <span class="keyword">null</span>;</span><br><span class="line"> Object oldProxy = <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">boolean</span> setProxyContext = <span class="keyword">false</span>;</span><br><span class="line"></span><br><span class="line"> TargetSource targetSource = <span class="keyword">this</span>.advised.targetSource;</span><br><span class="line"> Class targetClass = <span class="keyword">null</span>;</span><br><span class="line"> Object target = <span class="keyword">null</span>;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//eqauls()方法，具目标对象未实现此方法</span></span><br><span class="line"> <span class="keyword">if</span> (!<span class="keyword">this</span>.equalsDefined && AopUtils.isEqualsMethod(method)){</span><br><span class="line"> <span class="keyword">return</span> (equals(args[<span class="number">0</span>])? Boolean.TRUE : Boolean.FALSE);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//hashCode()方法，具目标对象未实现此方法</span></span><br><span class="line"> <span class="keyword">if</span> (!<span class="keyword">this</span>.hashCodeDefined && AopUtils.isHashCodeMethod(method)){</span><br><span class="line"> <span class="keyword">return</span> newInteger(hashCode());</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//Advised接口或者其父接口中定义的方法,直接反射调用,不应用通知</span></span><br><span class="line"> <span class="keyword">if</span> (!<span class="keyword">this</span>.advised.opaque &&method.getDeclaringClass().isInterface()</span><br><span class="line"> &&method.getDeclaringClass().isAssignableFrom(Advised.class)) {</span><br><span class="line"> <span class="comment">// Service invocations onProxyConfig with the proxy config...</span></span><br><span class="line"> <span class="keyword">return</span> AopUtils.invokeJoinpointUsingReflection(<span class="keyword">this</span>.advised,method, args);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> Object retVal = <span class="keyword">null</span>;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">if</span> (<span class="keyword">this</span>.advised.exposeProxy) {</span><br><span class="line"> <span class="comment">// Make invocation available ifnecessary.</span></span><br><span class="line"> oldProxy = AopContext.setCurrentProxy(proxy);</span><br><span class="line"> setProxyContext = <span class="keyword">true</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//获得目标对象的类</span></span><br><span class="line"> target = targetSource.getTarget();</span><br><span class="line"> <span class="keyword">if</span> (target != <span class="keyword">null</span>) {</span><br><span class="line"> targetClass = target.getClass();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//获取可以应用到此方法上的Interceptor列表</span></span><br><span class="line"> List chain = <span class="keyword">this</span>.advised.getInterceptorsAndDynamicInterceptionAdvice(method,targetClass);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//如果没有可以应用到此方法的通知(Interceptor)，此直接反射调用 method.invoke(target, args)</span></span><br><span class="line"> <span class="keyword">if</span> (chain.isEmpty()) {</span><br><span class="line"> retVal = AopUtils.invokeJoinpointUsingReflection(target,method, args);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">//创建MethodInvocation</span></span><br><span class="line"> invocation = newReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);</span><br><span class="line"> retVal = invocation.proceed();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">// Massage return value if necessary.</span></span><br><span class="line"> <span class="keyword">if</span> (retVal != <span class="keyword">null</span> && retVal == target &&method.getReturnType().isInstance(proxy)</span><br><span class="line"> &&!RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {</span><br><span class="line"> <span class="comment">// Special case: it returned"this" and the return type of the method</span></span><br><span class="line"> <span class="comment">// is type-compatible. Notethat we can't help if the target sets</span></span><br><span class="line"> <span class="comment">// a reference to itself inanother returned object.</span></span><br><span class="line"> retVal = proxy;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> retVal;</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="keyword">if</span> (target != <span class="keyword">null</span> && !targetSource.isStatic()) {</span><br><span class="line"> <span class="comment">// Must have come fromTargetSource.</span></span><br><span class="line"> targetSource.releaseTarget(target);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (setProxyContext) {</span><br><span class="line"> <span class="comment">// Restore old proxy.</span></span><br><span class="line"> AopContext.setCurrentProxy(oldProxy);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<p>主流程可以简述为：获取可以应用到此方法上的通知链（Interceptor Chain）,如果有,则应用通知,并执行joinpoint; 如果没有,则直接反射执行joinpoint。而这里的关键是通知链是如何获取的以及它又是如何执行的，下面逐一分析下。</p>
<p>首先，从上面的代码可以看到，通知链是通过<code>Advised.getInterceptorsAndDynamicInterceptionAdvice()</code>这个方法来获取的,我们来看下这个方法的实现:</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></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> List<Object>getInterceptorsAndDynamicInterceptionAdvice(Method method, Class targetClass) {</span><br><span class="line"> MethodCacheKeycacheKey = <span class="keyword">new</span> MethodCacheKey(method);</span><br><span class="line"> List<Object>cached = <span class="keyword">this</span>.methodCache.get(cacheKey);</span><br><span class="line"> <span class="keyword">if</span>(cached == <span class="keyword">null</span>) {</span><br><span class="line"> cached= <span class="keyword">this</span>.advisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice(</span><br><span class="line"> <span class="keyword">this</span>,method, targetClass);</span><br><span class="line"> <span class="keyword">this</span>.methodCache.put(cacheKey,cached);</span><br><span class="line"> }</span><br><span class="line"> returncached;</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<p>可以看到实际的获取工作其实是由<code>AdvisorChainFactory. getInterceptorsAndDynamicInterceptionAdvice()</code>这个方法来完成的，获取到的结果会被缓存。<br>下面来分析下这个方法的实现：</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></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * 从提供的配置实例config中获取advisor列表,遍历处理这些advisor.如果是IntroductionAdvisor,</span><br><span class="line"> * 则判断此Advisor能否应用到目标类targetClass上.如果是PointcutAdvisor,则判断</span><br><span class="line"> * 此Advisor能否应用到目标方法method上.将满足条件的Advisor通过AdvisorAdaptor转化成Interceptor列表返回.</span><br><span class="line"> */</span></span><br><span class="line"> <span class="function">publicList <span class="title">getInterceptorsAndDynamicInterceptionAdvice</span><span class="params">(Advised config, Methodmethod, Class targetClass)</span> </span>{</span><br><span class="line"> <span class="comment">// This is somewhat tricky... we have to process introductions first,</span></span><br><span class="line"> <span class="comment">// but we need to preserve order in the ultimate list.</span></span><br><span class="line"> List interceptorList = <span class="keyword">new</span> ArrayList(config.getAdvisors().length);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//查看是否包含IntroductionAdvisor</span></span><br><span class="line"> <span class="keyword">boolean</span> hasIntroductions = hasMatchingIntroductions(config,targetClass);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//这里实际上注册一系列AdvisorAdapter,用于将Advisor转化成MethodInterceptor</span></span><br><span class="line"> AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();</span><br><span class="line"></span><br><span class="line"> Advisor[] advisors = config.getAdvisors();</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i <advisors.length; i++) {</span><br><span class="line"> Advisor advisor = advisors[i];</span><br><span class="line"> <span class="keyword">if</span> (advisor <span class="keyword">instanceof</span> PointcutAdvisor) {</span><br><span class="line"> <span class="comment">// Add it conditionally.</span></span><br><span class="line"> PointcutAdvisor pointcutAdvisor= (PointcutAdvisor) advisor;</span><br><span class="line"> <span class="keyword">if</span>(config.isPreFiltered() ||pointcutAdvisor.getPointcut().getClassFilter().matches(targetClass)) {</span><br><span class="line"> <span class="comment">//<span class="doctag">TODO:</span> 这个地方这两个方法的位置可以互换下</span></span><br><span class="line"> <span class="comment">//将Advisor转化成Interceptor</span></span><br><span class="line"> MethodInterceptor[]interceptors = registry.getInterceptors(advisor);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//检查当前advisor的pointcut是否可以匹配当前方法</span></span><br><span class="line"> MethodMatcher mm =pointcutAdvisor.getPointcut().getMethodMatcher();</span><br><span class="line"></span><br><span class="line"> <span class="keyword">if</span> (MethodMatchers.matches(mm,method, targetClass, hasIntroductions)) {</span><br><span class="line"> <span class="keyword">if</span>(mm.isRuntime()) {</span><br><span class="line"> <span class="comment">// Creating a newobject instance in the getInterceptors() method</span></span><br><span class="line"> <span class="comment">// isn't a problemas we normally cache created chains.</span></span><br><span class="line"> <span class="keyword">for</span> (intj = <span class="number">0</span>; j < interceptors.length; j++) {</span><br><span class="line"> interceptorList.add(<span class="keyword">new</span> InterceptorAndDynamicMethodMatcher(interceptors[j],mm));</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> interceptorList.addAll(Arrays.asList(interceptors));</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (advisor <span class="keyword">instanceof</span> IntroductionAdvisor){</span><br><span class="line"> IntroductionAdvisor ia =(IntroductionAdvisor) advisor;</span><br><span class="line"> <span class="keyword">if</span>(config.isPreFiltered() || ia.getClassFilter().matches(targetClass)) {</span><br><span class="line"> Interceptor[] interceptors= registry.getInterceptors(advisor);</span><br><span class="line"> interceptorList.addAll(Arrays.asList(interceptors));</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> Interceptor[] interceptors =registry.getInterceptors(advisor);</span><br><span class="line"> interceptorList.addAll(Arrays.asList(interceptors));</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> interceptorList;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>这个方法执行完成后，Advised中配置能够应用到连接点或者目标类的Advisor全部被转化成了MethodInterceptor.</p>
<p>接下来我们再看下得到的拦截器链是怎么起作用的。</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></pre></td><td class="code"><pre><span class="line"><span class="keyword">if</span> (chain.isEmpty()) {</span><br><span class="line"> retVal = AopUtils.invokeJoinpointUsingReflection(target,method, args);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">//创建MethodInvocation</span></span><br><span class="line"> invocation = newReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);</span><br><span class="line"> retVal = invocation.proceed();</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<p> 从这段代码可以看出，如果得到的拦截器链为空，则直接反射调用目标方法，否则创建MethodInvocation，调用其proceed方法，触发拦截器链的执行，来看下具体代码</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><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="function"><span class="keyword">public</span> Object <span class="title">proceed</span><span class="params">()</span> <span class="keyword">throws</span> Throwable </span>{</span><br><span class="line"> <span class="comment">// We start with an index of -1and increment early.</span></span><br><span class="line"> <span class="keyword">if</span> (<span class="keyword">this</span>.currentInterceptorIndex == <span class="keyword">this</span>.interceptorsAndDynamicMethodMatchers.size()- <span class="number">1</span>) {</span><br><span class="line"> <span class="comment">//如果Interceptor执行完了，则执行joinPoint</span></span><br><span class="line"> <span class="keyword">return</span> invokeJoinpoint();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> Object interceptorOrInterceptionAdvice =</span><br><span class="line"> <span class="keyword">this</span>.interceptorsAndDynamicMethodMatchers.get(++<span class="keyword">this</span>.currentInterceptorIndex);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//如果要动态匹配joinPoint</span></span><br><span class="line"> <span class="keyword">if</span> (interceptorOrInterceptionAdvice <span class="keyword">instanceof</span> InterceptorAndDynamicMethodMatcher){</span><br><span class="line"> <span class="comment">// Evaluate dynamic method matcher here: static part will already have</span></span><br><span class="line"> <span class="comment">// been evaluated and found to match.</span></span><br><span class="line"> InterceptorAndDynamicMethodMatcher dm =</span><br><span class="line"> (InterceptorAndDynamicMethodMatcher)interceptorOrInterceptionAdvice;</span><br><span class="line"> <span class="comment">//动态匹配：运行时参数是否满足匹配条件</span></span><br><span class="line"> <span class="keyword">if</span> (dm.methodMatcher.matches(<span class="keyword">this</span>.method, <span class="keyword">this</span>.targetClass,<span class="keyword">this</span>.arguments)) {</span><br><span class="line"> <span class="comment">//执行当前Intercetpor</span></span><br><span class="line"> returndm.interceptor.invoke(<span class="keyword">this</span>);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">//动态匹配失败时,略过当前Intercetpor,调用下一个Interceptor</span></span><br><span class="line"> <span class="keyword">return</span> proceed();</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">// It's an interceptor, so we just invoke it: The pointcutwill have</span></span><br><span class="line"> <span class="comment">// been evaluated statically before this object was constructed.</span></span><br><span class="line"> <span class="comment">//执行当前Intercetpor</span></span><br><span class="line"> <span class="keyword">return</span> ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(<span class="keyword">this</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>代码也比较简单，这里不再赘述。</p>
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jdk动态代理实现原理
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<p>写在前面:</p>
<ul>
<li>大神和diao炸天的亲请绕道..</li>
<li>关于代理模式的概念这里省去,大家可以放鸟尽情搜..</li>
<li>关于为什么叫动态代理,个人理解是代理的类是在运行时动态生成的,大家也可以参考网上的理解..</li>
<li>文笔很差,所以文字较少,都在代码和注释中..</li>
</ul>
<p>=======一点不华丽的分割线————————-</p>
<p>开门见山,lets go..</p>
<p>java中可以通过jdk提供的 Proxy.newProxyInstance静态方法来创建动态代理对象,下面先来看看这个方法的实现</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></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> Object <span class="title">newProxyInstance</span><span class="params">(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h)</span></span><br><span class="line"> <span class="keyword">throws</span> IllegalArgumentException </span>{</span><br><span class="line"> <span class="comment">//InvocationHandler不能为空,因为对代理对象的所有方法调用实际上都会委托到InvocationHandler的invoke方法,</span></span><br><span class="line"> <span class="comment">//这个我们后面通过查看产生的代理类的源代码便会一目了然</span></span><br><span class="line"> <span class="keyword">if</span> (h == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> NullPointerException();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//这个是核心的地方,通过提供的ClassLoader和interface列表来产生代理类,具体的实现可以参考getProxyClass这个方法的实现,</span></span><br><span class="line"> <span class="comment">//真正的工作是由sun.misc.ProxyGenerator这个类来完成的,可以google查看具体的逻辑.在我们的程序中通过设置</span></span><br><span class="line"> <span class="comment">//System.setProperty("sun.misc.ProxyGenerator.saveGeneratedFiles", "true")可以查看产生的类文件</span></span><br><span class="line"> Class cl = getProxyClass(loader, interfaces);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//因为代理类继承了Proxy类.而Proxy中定义了构造函数protected Proxy(InvocationHandler h),所以可以反射得到Constructer实例</span></span><br><span class="line"> <span class="comment">//创建代理对象</span></span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> Constructor cons = cl.getConstructor(constructorParams);</span><br><span class="line"> <span class="keyword">return</span> (Object) cons.newInstance(<span class="keyword">new</span> Object[] { h });</span><br><span class="line"> } <span class="keyword">catch</span> (NoSuchMethodException e) {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> InternalError(e.toString());</span><br><span class="line"> } <span class="keyword">catch</span> (IllegalAccessException e) {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> InternalError(e.toString());</span><br><span class="line"> } <span class="keyword">catch</span> (InstantiationException e) {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> InternalError(e.toString());</span><br><span class="line"> } <span class="keyword">catch</span> (InvocationTargetException e) {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> InternalError(e.toString());</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>下面通过个例子来说明下:<br>先来定义一个接口,jdk的动态代理基于接口来创建代理类,不能基于类的原因是java不支持多重继承,而代理类都会继承Proxy类(个人理解).</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="comment">/**</span><br><span class="line"> * Subject</span><br><span class="line"> *</span><br><span class="line"> * <span class="doctag">@author</span> Kevin Fan</span><br><span class="line"> * <span class="doctag">@since</span> 2013-9-13 下午2:43:33</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">Subject</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">pub</span><span class="params">(String key, String content)</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="function">String <span class="title">sub</span><span class="params">(String key)</span></span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>再来一个具体的实现,在代理模式中可以叫它的实例可以叫target,这个是真正执行操作的对象</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></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * SimpleSubject</span><br><span class="line"> *</span><br><span class="line"> * <span class="doctag">@author</span> Kevin Fan</span><br><span class="line"> * <span class="doctag">@since</span> 2013-9-13 下午2:45:03</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">SimpleSubject</span> <span class="keyword">implements</span> <span class="title">Subject</span> </span>{</span><br><span class="line"> <span class="keyword">private</span> Map<String, String> msg = <span class="keyword">new</span> ConcurrentHashMap<String, String>();</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">pub</span><span class="params">(String key, String content)</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"pub msg: key is "</span> + key + <span class="string">", content is "</span> + content);</span><br><span class="line"> msg.put(key, content);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> String <span class="title">sub</span><span class="params">(String key)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (msg.containsKey(key)) {</span><br><span class="line"> String ret = msg.get(key);</span><br><span class="line"> System.out.println(<span class="string">"sub msg: key is "</span> + key + <span class="string">", result is "</span> + ret);</span><br><span class="line"> <span class="keyword">return</span> ret;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>好,接下来我们来写个动态代理工厂,根据 不同的target来创建动态代理对象</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="comment">/**</span><br><span class="line"> * SubjectProxyFactory</span><br><span class="line"> *</span><br><span class="line"> * <span class="doctag">@author</span> Kevin Fan</span><br><span class="line"> * <span class="doctag">@since</span> 2013-9-13 下午2:47:24</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">SubjectProxyFactory</span> </span>{</span><br><span class="line"> <span class="comment">//<span class="doctag">TODO:</span> cache</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> Subject <span class="title">getSubject</span><span class="params">(<span class="keyword">final</span> Subject realSubject)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> (Subject) Proxy.newProxyInstance(realSubject.getClass().getClassLoader(), <span class="keyword">new</span> Class[] { Subject.class },</span><br><span class="line"> <span class="keyword">new</span> InvocationHandler() {</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> Object <span class="title">invoke</span><span class="params">(Object proxy, Method method, Object[] args)</span> <span class="keyword">throws</span> Throwable </span>{</span><br><span class="line"> System.out.println(<span class="string">"\naction before method invocation...."</span>);</span><br><span class="line"> Object retVal = method.invoke(realSubject, args);</span><br><span class="line"> System.out.println(<span class="string">"action after method invocation....\n"</span>);</span><br><span class="line"> <span class="keyword">return</span> retVal;</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>
<p>可以看到这是一个简单的实现,只是在真实对象执行前后各打一句信息..</p>
<p>接下来用一个 main函数来把这些结合起来</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></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Demo</span><br><span class="line"> *</span><br><span class="line"> * <span class="doctag">@author</span> Kevin Fan</span><br><span class="line"> * <span class="doctag">@since</span> 2013-9-13 下午2:50:28</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Demo</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>{</span><br><span class="line"> <span class="comment">//设置此系统属性,以查看代理类文件</span></span><br><span class="line"> System.setProperty(<span class="string">"sun.misc.ProxyGenerator.saveGeneratedFiles"</span>, <span class="string">"true"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//创建真实对象</span></span><br><span class="line"> Subject subj = <span class="keyword">new</span> SimpleSubject();</span><br><span class="line"> subj.pub(<span class="string">"name"</span>, <span class="string">"kevin.fan"</span>);</span><br><span class="line"> subj.sub(<span class="string">"name"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//创建代理对象</span></span><br><span class="line"> Subject proxy = SubjectProxyFactory.getSubject(subj);</span><br><span class="line"> proxy.pub(<span class="string">"hobby"</span>, <span class="string">"r&b music"</span>);</span><br><span class="line"> proxy.sub(<span class="string">"name"</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>ok,小手抖一下,走你,看下执行结果</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">pub msg: key is name, content is kevin.fan</span><br><span class="line">sub msg: key is name, result is kevin.fan</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">action before method invocation....</span><br><span class="line">pub msg: key is hobby, content is r&b music</span><br><span class="line">action after method invocation....</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">action before method invocation....</span><br><span class="line">sub msg: key is name, result is kevin.fan</span><br><span class="line">action after method invocation....</span><br></pre></td></tr></table></figure>
<p>可以看到在调用代理对象的方法时,添加的额外动作已经生效,接下来我们看下生成的代理类的代码..</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><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 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class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br><span class="line">119</span><br><span class="line">120</span><br><span class="line">121</span><br><span class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br><span class="line">128</span><br><span class="line">129</span><br><span class="line">130</span><br><span class="line">131</span><br><span class="line">132</span><br><span class="line">133</span><br><span class="line">134</span><br><span class="line">135</span><br><span class="line">136</span><br><span class="line">137</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> com.aliyun.demo.kevin.coder.lang.proxy.Subject;</span><br><span class="line"><span class="keyword">import</span> java.lang.reflect.InvocationHandler;</span><br><span class="line"><span class="keyword">import</span> java.lang.reflect.Method;</span><br><span class="line"><span class="keyword">import</span> java.lang.reflect.Proxy;</span><br><span class="line"><span class="keyword">import</span> java.lang.reflect.UndeclaredThrowableException;</span><br><span class="line"></span><br><span class="line"><span class="comment">//这里很清楚了,代理类继承了Proxy类,并且实现了Proxy.newProxyInstance这个方法中传入的接口</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">final</span> <span class="class"><span class="keyword">class</span> $<span class="title">Proxy0</span> <span class="keyword">extends</span> <span class="title">Proxy</span></span><br><span class="line"><span class="keyword">implements</span> <span class="title">Subject</span></span><br><span class="line"></span>{</span><br><span class="line"></span><br><span class="line"> <span class="comment">//这些方法在下面的static init block中进行初始化</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> Method m4;</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> Method m1;</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> Method m3;</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> Method m0;</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> Method m2;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">static</span></span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">try</span></span><br><span class="line"> {</span><br><span class="line"> m4 = Class.forName(<span class="string">"com.aliyun.demo.kevin.coder.lang.proxy.Subject"</span>).getMethod(<span class="string">"sub"</span>, <span class="keyword">new</span> Class[] { Class.forName(<span class="string">"java.lang.String"</span>) });</span><br><span class="line"> m1 = Class.forName(<span class="string">"java.lang.Object"</span>).getMethod(<span class="string">"equals"</span>, <span class="keyword">new</span> Class[] { Class.forName(<span class="string">"java.lang.Object"</span>) });</span><br><span class="line"> m3 = Class.forName(<span class="string">"com.aliyun.demo.kevin.coder.lang.proxy.Subject"</span>).getMethod(<span class="string">"pub"</span>, <span class="keyword">new</span> Class[] { Class.forName(<span class="string">"java.lang.String"</span>), Class.forName(<span class="string">"java.lang.String"</span>) });</span><br><span class="line"> m0 = Class.forName(<span class="string">"java.lang.Object"</span>).getMethod(<span class="string">"hashCode"</span>, <span class="keyword">new</span> Class[<span class="number">0</span>]);</span><br><span class="line"> m2 = Class.forName(<span class="string">"java.lang.Object"</span>).getMethod(<span class="string">"toString"</span>, <span class="keyword">new</span> Class[<span class="number">0</span>]);</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (NoSuchMethodException localNoSuchMethodException)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> NoSuchMethodError(localNoSuchMethodException.getMessage());</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (ClassNotFoundException localClassNotFoundException)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> NoClassDefFoundError(localClassNotFoundException.getMessage());</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//构造函数,接收一个 InvocationHandler作为参数,这就是为什么Proxy.newProxyInstance方法里可以</span></span><br><span class="line"> <span class="comment">//通过InvocationHandler实例作为参数来反射获取Constructer实例</span></span><br><span class="line"> <span class="keyword">public</span> $Proxy0 paramInvocationHandler)</span><br><span class="line"> <span class="keyword">throws</span></span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">super</span>(paramInvocationHandler);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//下面通过这个来看下代理对象中方法是怎样调用的</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">final</span> String <span class="title">sub</span><span class="params">(String paramString)</span></span><br><span class="line"> <span class="keyword">throws</span></span><br><span class="line"> </span>{</span><br><span class="line"> <span class="keyword">try</span></span><br><span class="line"> {</span><br><span class="line"> <span class="comment">//全部是通过调用InvocationHandler的invoke方法,传入对应的方法和参数</span></span><br><span class="line"> <span class="keyword">return</span> (String)<span class="keyword">this</span>.h.invoke(<span class="keyword">this</span>, m4, <span class="keyword">new</span> Object[] { paramString });</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (Error|RuntimeException localError)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> localError;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (Throwable localThrowable)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> UndeclaredThrowableException(localThrowable);</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">public</span> <span class="keyword">final</span> <span class="keyword">boolean</span> <span class="title">equals</span><span class="params">(Object paramObject)</span></span><br><span class="line"> <span class="keyword">throws</span></span><br><span class="line"> </span>{</span><br><span class="line"> <span class="keyword">try</span></span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">return</span> ((Boolean)<span class="keyword">this</span>.h.invoke(<span class="keyword">this</span>, m1, <span class="keyword">new</span> Object[] { paramObject })).booleanValue();</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (Error|RuntimeException localError)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> localError;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (Throwable localThrowable)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> UndeclaredThrowableException(localThrowable);</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">public</span> <span class="keyword">final</span> <span class="keyword">void</span> <span class="title">pub</span><span class="params">(String paramString1, String paramString2)</span></span><br><span class="line"> <span class="keyword">throws</span></span><br><span class="line"> </span>{</span><br><span class="line"> <span class="keyword">try</span></span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">this</span>.h.invoke(<span class="keyword">this</span>, m3, <span class="keyword">new</span> Object[] { paramString1, paramString2 });</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (Error|RuntimeException localError)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> localError;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (Throwable localThrowable)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> UndeclaredThrowableException(localThrowable);</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">public</span> <span class="keyword">final</span> <span class="keyword">int</span> <span class="title">hashCode</span><span class="params">()</span></span><br><span class="line"> <span class="keyword">throws</span></span><br><span class="line"> </span>{</span><br><span class="line"> <span class="keyword">try</span></span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">return</span> ((Integer)<span class="keyword">this</span>.h.invoke(<span class="keyword">this</span>, m0, <span class="keyword">null</span>)).intValue();</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (Error|RuntimeException localError)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> localError;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (Throwable localThrowable)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> UndeclaredThrowableException(localThrowable);</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">public</span> <span class="keyword">final</span> String <span class="title">toString</span><span class="params">()</span></span><br><span class="line"> <span class="keyword">throws</span></span><br><span class="line"> </span>{</span><br><span class="line"> <span class="keyword">try</span></span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">return</span> (String)<span class="keyword">this</span>.h.invoke(<span class="keyword">this</span>, m2, <span class="keyword">null</span>);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (Error|RuntimeException localError)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> localError;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">catch</span> (Throwable localThrowable)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> UndeclaredThrowableException(localThrowable);</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>
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<a class="post-title-link" href="/2012/11/29/junit-test-java-io-speed/" itemprop="url">
Java IO读取速度测试
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2012-11-29
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<p>不知道是什么情况，今天喜欢上了看IO这个东东。。回来码了几行简单的不能再简单的代码 ，跑了一把，得了几个 数据 ，放到这里跟大家分享下。。<br>先把测试的结果截图摆上来欣赏一下：有一点需要说明的是，前四个方法是以字节流的形式读取一个大小为11M左右的rar文件，后面两个 方法是以字符流的形式读取在小在1M~2M之间的一个文本文件~</p>
<p><img src="/images/java-io-speed.jpg" alt=""></p>
<p>具体每个方法是怎么实现 的，代码简单到了什么程度，常用到了什么程度 。。。。。。<br>话不多说，元芳，代码在这里，你怎么看？</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><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</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">IOSpeedTest</span> </span>{</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> String file = <span class="string">"G:\\pt.rar"</span>;</span><br><span class="line"></span><br><span class="line"> <span class="annotation">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">testWithoutBuf</span><span class="params">()</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> <span class="keyword">int</span> line = <span class="number">0</span>;</span><br><span class="line"> FileInputStream in = <span class="keyword">new</span> FileInputStream(file);</span><br><span class="line"> <span class="keyword">int</span> bit = -<span class="number">1</span>;</span><br><span class="line"> <span class="keyword">while</span> ((bit = in.read()) != -<span class="number">1</span>) {</span><br><span class="line"> <span class="keyword">if</span> (bit == <span class="string">'\n'</span>) {</span><br><span class="line"> ++line;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (in != <span class="keyword">null</span>) {</span><br><span class="line"> in.close();</span><br><span class="line"> }</span><br><span class="line"> System.out.println(line);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="annotation">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">testWithBufferedIn</span><span class="params">()</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> BufferedInputStream in = <span class="keyword">new</span> BufferedInputStream(<span class="keyword">new</span> FileInputStream(file));</span><br><span class="line"> <span class="keyword">int</span> line = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">int</span> bit = -<span class="number">1</span>;</span><br><span class="line"> <span class="keyword">while</span> ((bit = in.read()) != -<span class="number">1</span>) {</span><br><span class="line"> <span class="keyword">if</span> (bit == <span class="string">'\n'</span>) {</span><br><span class="line"> ++line;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (in != <span class="keyword">null</span>) {</span><br><span class="line"> in.close();</span><br><span class="line"> }</span><br><span class="line"> System.out.println(line);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="annotation">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">testWithFixedBuf</span><span class="params">()</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> <span class="keyword">int</span> bufSize = <span class="number">8196</span>;</span><br><span class="line"> FileInputStream in = <span class="keyword">new</span> FileInputStream(file);</span><br><span class="line"> <span class="keyword">int</span> line = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">byte</span>[] buf = <span class="keyword">new</span> <span class="keyword">byte</span>[bufSize];</span><br><span class="line"> <span class="keyword">while</span> (in.read(buf) != -<span class="number">1</span>) {</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">byte</span> element : buf) {</span><br><span class="line"> <span class="keyword">if</span> (element == <span class="string">'\n'</span>) {</span><br><span class="line"> ++line;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (in != <span class="keyword">null</span>) {</span><br><span class="line"> in.close();</span><br><span class="line"> }</span><br><span class="line"> System.out.println(line);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="annotation">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">testWithWholeFile</span><span class="params">()</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> FileInputStream in = <span class="keyword">new</span> FileInputStream(file);</span><br><span class="line"> <span class="keyword">int</span> line = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">byte</span>[] buf = <span class="keyword">new</span> <span class="keyword">byte</span>[file.length()];</span><br><span class="line"> in.read(buf);</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">byte</span> element : buf) {</span><br><span class="line"> <span class="keyword">if</span> (element == <span class="string">'\n'</span>) {</span><br><span class="line"> ++line;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (in != <span class="keyword">null</span>) {</span><br><span class="line"> in.close();</span><br><span class="line"> }</span><br><span class="line"> System.out.println(line);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> String txt = <span class="string">"G:\\cy.txt"</span>;</span><br><span class="line"></span><br><span class="line"> <span class="annotation">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">testWithBf</span><span class="params">()</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> BufferedReader bf = <span class="keyword">new</span> BufferedReader(<span class="keyword">new</span> InputStreamReader(<span class="keyword">new</span> FileInputStream(txt)));</span><br><span class="line"> <span class="keyword">while</span> (bf.readLine() != <span class="keyword">null</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 class="annotation">@Test</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">testWithFixedBf</span><span class="params">()</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> <span class="keyword">int</span> bufSize = <span class="number">8196</span>;</span><br><span class="line"> InputStreamReader reader = <span class="keyword">new</span> InputStreamReader(<span class="keyword">new</span> FileInputStream(txt));</span><br><span class="line"> <span class="keyword">char</span>[] buf = <span class="keyword">new</span> <span class="keyword">char</span>[bufSize];</span><br><span class="line"> <span class="keyword">while</span> (reader.read(buf) != -<span class="number">1</span>) {</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"> reader.close();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>好长时间没有自己写过文章了，今天写这么水的东西出来，求轻喷。。~~<br>kevin 11/29/2012</p>
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