isis-module-freemarker

Table of Contents

• How to configure/use
  • "Out-of-the-box"
  • "Out-of-the-box" (-SNAPSHOT)
  • Forking the repo
• API
  • FreeMarker’s Design
  • FreeMarkerService
• Example Usage
• Change Log
• Legal Stuff
  • License
• Maven deploy notes
  • Release to Sonatype’s Snapshot Repo
  • Release an Interim Build
  • Release to Maven Central

This module, intended for use with Apache Isis, provides a wrapper around Freemarker templating engine.

How to configure/use

You can either use this module "out-of-the-box", or you can fork this repo and extend to your own requirements.

"Out-of-the-box"

To use "out-of-the-box":

• update your classpath by adding this dependency in your dom project’s pom.xml:
  

  <dependency>
      <groupId>org.isisaddons.module.freemarker</groupId>
      <artifactId>isis-module-freemarker-dom</artifactId>
      <version>1.14.0</version>
  </dependency>

• update the getModules() method of your AppManifest:
  

  @Override
  public List<Class<?>> getModules() {
      return Arrays.asList(
              ...
              org.isisaddons.module.freemarker.dom.FreeMarkerModule.class,
              ...
      );
  }

• optionally, enable/disable JODA support using a configuration property (in isis.properties, or in the AppManifest):
  

  isis.services.addons.freemarker.jodaSupport=true

  If not specified, then JODA support is enabled.

"Out-of-the-box" (-SNAPSHOT)

If you want to use the current -SNAPSHOT, then the steps are the same as above, except:

• when updating the classpath, specify the appropriate -SNAPSHOT version:
  

  <version>1.15.0-SNAPSHOT</version>

• add the repository definition to pick up the most recent snapshot (we use the Cloudbees continuous integration service). We suggest defining the repository in a <profile>:
  

  <profile>
      <id>cloudbees-snapshots</id>
      <activation>
          <activeByDefault>true</activeByDefault>
      </activation>
      <repositories>
          <repository>
              <id>snapshots-repo</id>
              <url>http://repository-estatio.forge.cloudbees.com/snapshot/</url>
              <releases>
                  <enabled>false</enabled>
              </releases>
              <snapshots>
                  <enabled>true</enabled>
              </snapshots>
          </repository>
      </repositories>
  </profile>

Forking the repo

If instead you want to extend this module’s functionality, then we recommend that you fork this repo. The repo is structured as follows:

• pom.xml - parent pom

• dom - the module implementation, depends on Isis applib

API

In order to understand the API of the service provided by this module (FreeMarkService), it’s necessary to understand a little of the API/SPI exposed by FreeMarker itself.

FreeMarker’s Design

Freemarker’s design is that templates are identified by a template name and a version. Freemarker’s TemplateLoader SPI is used to lookup the template text and to check whether that template text is stale; Freemarker automatically caches any template text and only reads in new text if a "lastModified" property has changed. The sequence is:

• calls `TemplateLoader#findTemplateSource(templateName)
  

  to look up an object that can act as the source of the template text (can return a reader). For example, this templateName might just be a file name.

• then calls TemplateLoader#getLastModified(templateSource)
  

  to determine the time (ie versoin) of this particular source. For example, if the template source is a file, then this would be the lastModified timestamp on this file.

• if necessary, then calls TemplateLoader#getReader(templateSource, encoding).
  

  Freemarker automatically caches template text, so it will only make this call if the templateSource returns a newer lastModified timestamp than cached.

When FreeMarker passes in the templateName to #findTemplateSource(.) it also appends a locale, eg "_en_GB". The idea, obviously, is that locale-specific versions of templates can be returned.

FreeMarkerService

This module provides a single service, called FreeMarkerService. It has the following API:

@DomainService(nature = NatureOfService.DOMAIN)
public class FreeMarkerService {
    public String render(
            String templateName,                        // (1)
            long version,                               // (2)
            String templateChars,                       // (3)
            Object dataModel)                           // (4)
        throws IOException, TemplateException;
}

1. the name/version of the template, corresponding directly to FreeMarker’s "templateName".

2. the templateChars is the actual template text itself

3. the dataModel is the object whose values are interpolated by Freemarker into the template. This can either be a strongly typed DTO or just a simple Map.

This method takes parameters that (from FreeMarker’s point of view) represent both the input to finding a template and also the output (the text of that template):

• the templateName broadly corresponds directly to FreeMarker’s "templateName".
  

  To support multiple versions of a template over time, just create a composite name. Similarly, if multiple versions of a template are needed for different app tenancies, combine that into the composite name also.
  

  For example, to support two versions of an "InvoiceTemplate" for France and for Italy, each published on 1 Dec 2015, one could pass in a template of "Invoice:/FRA:2015-12-01" or "Invoice:/ITA:2015-12-01".

• the templateChars is the template text that is used to return a StringReader if and when FreeMarker calls #getReader(…​).

Internally FreeMarker caches the template characters; it uses the templateName and the version as a way to determine whether its internal cache is invalid. As a small wrinkle, it also performs the caching on a per-locale basis; the templateName used internally will have a locale appended to it (eg "_en_GB").

All this caching is irrelevant to the FreeMarkerService, because it passes in the template characters irrespective; these are simply made available on a thread-local. The responsibility for caching therefore moves outside of FreeMarker, and to the calling application. Thus, the intended usage is that the template characters will be stored in an entity (let’s call it DocumentTemplate, say) which could be identified by documentType and atPath, say, and which also is versioned. The documentType and atPath can simply be joined together to create the logical template name.

Note

FreeMarker also supports the notion of versioned templates (the TemplateSourc#getLastModified() API), however there’s clearly a subtlety going on somewhere because in an earlier design of this service (which took in a version parameter for the template) it didn’t seem to work. Since in most cases the templateName is likely to be a composite anyway (for application tenancy), the decision is simply to also include the version number as well in this "template name".

Example Usage

From the unit tests:

// given
 Map<String, String> properties = ImmutableMap.of("user", "John Doe");

// when
String merged = service.render("WelcomeUserTemplate:/GBR:2015-12-01:", "<h1>Welcome ${user}!</h1>",  properties);

// then
assertThat(merged, is("<h1>Welcome John Doe!</h1>"));

Change Log

• 1.14.0 - released against Isis 1.14.0

• 1.13.2 - released against Isis 1.13.2. Fixes #1 - automatic support for JODA dates and time (can be disabled using configuration property)

• 1.13.1 - released against Isis 1.13.0. NB: this is a breaking change, with a simpler API.

• 1.13.0 - released against Isis 1.13.0

Legal Stuff

License

Copyright 2016-2017 Dan Haywood

Licensed under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.

Maven deploy notes

Only the dom module is deployed, and is done so using Sonatype’s OSS support (see user guide).

Release to Sonatype’s Snapshot Repo

To deploy a snapshot, use:

pushd dom
mvn clean deploy
popd

The artifacts should be available in Sonatype’s Snapshot Repo.

Release an Interim Build

If you have commit access to this project (or a fork of your own) then you can create interim releases using the interim-release.sh script.

The idea is that this will - in a new branch - update the dom/pom.xml with a timestamped version (eg 1.14.0.20170227-0738). It then pushes the branch (and a tag) to the specified remote.

A CI server such as Jenkins can monitor the branches matching the wildcard origin/interim/* and create a build. These artifacts can then be published to a snapshot repository.

For example:

sh interim-release.sh 1.14.0 origin

where

• 1.14.0 is the base release

• origin is the name of the remote to which you have permissions to write to.

Release to Maven Central

The release.sh script automates the release process. It performs the following:

• performs a sanity check (mvn clean install -o) that everything builds ok

• bumps the pom.xml to a specified release version, and tag

• performs a double check (mvn clean install -o) that everything still builds ok

• releases the code using mvn clean deploy

• bumps the pom.xml to a specified release version

For example:

sh release.sh 1.14.0 \
              1.15.0-SNAPSHOT \
              dan@haywood-associates.co.uk \
              "this is not really my passphrase"

where

• $1 is the release version

• $2 is the snapshot version

• $3 is the email of the secret key (~/.gnupg/secring.gpg) to use for signing

• $4 is the corresponding passphrase for that secret key.

Other ways of specifying the key and passphrase are available, see the `pgp-maven-plugin’s documentation).

If the script completes successfully, then push changes:

git push origin master && git push origin 1.14.0

If the script fails to complete, then identify the cause, perform a git reset --hard to start over and fix the issue before trying again. Note that in the dom’s `pom.xml the nexus-staging-maven-plugin has the autoReleaseAfterClose setting set to true (to automatically stage, close and the release the repo). You may want to set this to false if debugging an issue.

According to Sonatype’s guide, it takes about 10 minutes to sync, but up to 2 hours to update search.