Creating Plugins to extend Plugins

For Liferay plugins, you can create a new plugin that extends an existing one. By extending a plugin, you can use all its features in your new plugin while keeping your changes/extensions separate from the existing plugin’s source code.

To create a plugin which extends another, follow these steps:

1. Create a new empty plugin in the Plugins SDK.

2. Remove all the auto-generated files except build.xml and the docroot folder, which should be empty.

3. Copy the original WAR file of the plugin you’d like to extend (for example, social-networking-portlet-6.1.10.1-ee-ga1.war) to the root folder of your new plugin.

4. Add the following line to your build.xml inside of the <project> tag to reference the original WAR file you are going to extend:

   <property
       name="original.war.file"
       value="social-networking-portlet-6.1.10.1-ee-ga1.war"
   />
   

5. Copy any files from the original plugin that you’re overwriting to your new plugin (using the same folder structure) and run the Ant target merge. Please note that the merge target is called whenever the plugin is compiled. All you have to do is to check the Ant output:

   dsanz@host:~/sdk/portlets/my-social-networking-portlet$ ant war
   Buildfile: /home/dsanz/sdk/portlets/my-social-networking-portlet/build.xml
   
   compile:
   
   merge:
   [mkdir] Created dir: /home/dsanz/sdk/portlets/my-social-networking-portlet/tmp
   [mkdir] Created dir:
   /home/dsanz/sdk/portlets/my-social-networking-portlet/tmp/WEB-INF/classes 
   [mkdir] Created dir:
   /home/dsanz/sdk/portlets/my-social-networking-portlet/tmp/WEB-INF/lib 
   
   merge-unzip:
   [unzip] Expanding:
   /home/dsanz/sdk/portlets/my-social-networking-portlet/social-networking-portlet-
   6.1.10.1-ee-ga1.war into /home/dsanz/sdk/portlets/my-social-networking-portlet/t
   mp 
   [copy] Copying 2 files to
   /home/dsanz/sdk/portlets/my-social-networking-portlet/tmp 
   [mkdir] Created dir:
   /home/dsanz/sdk/portlets/my-social-networking-portlet/docroot/WEB-INF/classes 
   
   ...
   

6. If the plugin that you’re extending contains a service, you need to overwrite the ClpSerializer.java file. The Service Builder-generated ClpSerializer.java file contains a hard-coded project for _servletContextName. You need to change this to the name of your plugin.

This generates a plugin (you can find the WAR file in the /dist folder of your plugins SDK) which combines the original one with your changes.

In summary, if localization is important for your portlets, always consider statements in a localization plan, since some portlets in your plugin and hard customer requests can make a mess in your localization files and keys. If possible, reuse Liferay core language keys since they’re already translated for you.

If there’s no key you can use, you can create your own, as described in this chapter. Liferay gives you the tools to make localization possible, and uses a web service to provide rudimentary translations.