How to Add custom JAR to the "eclipse-pmd" plugin?

Question

Installed the Eclipse PMD plugin (written by Philip Graf) from here. I tried to associate a custom PMD rule classes JAR but couldn't find a provision for it. This JAR contains custom rule classes (that extends AbstractJavaRule indirectly).

So is there any way to configure eclipse-pmd plugin to accept this custom JAR?

My custompmd.jar has this structure:

custompmd.jar
└─com/pmd/custom
             └─AvoidHardcodingRule.class
             └─AvoidCatchWithoutLogErrorRule.class
             └─etc...

Simply putting it in plugins directory didn't help. One of the SO question suggests a solution but that's for a different plugin.

[UPDATE]
I am currently thinking of editing one of the eclipse\plugins\ch.acanda.eclipse.pmd.BLAHBLAH.jar, add custompmd.jar into the lib folder and updating META-INF\MANIFEST.MF file by appending the JAR information in the Bundle-ClassPath: section. Is it the right practice as patching the plugin JAR seems ugly to me?

[UPDATE]
The above approach didn't work.

Any of you Eclipse gurus know how to crack it?

[UPDATE]
I cracked it by myself.

[UPDATE]
Although the below solution works, it is a maintenance nightmare. Whenever, I change the custompmd.jar, I have to update the plugin JAR as well everytime, which is tedious. Is there a clean and neat solution?

Answer 1

You can use your custom rule classes if you add your jar as an Eclipse plug-in fragment to your Eclipse installation. The host of the plug-in fragment must be ch.acanda.eclipse.pmd.core.

To convert the jar to a plug-in fragment you have to modify the file MANIFEST.MF file and add a few manifest headers. The following is a complete manifest of an Eclipse plug-in fragment:

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: Custom PMD Rules
Bundle-SymbolicName: org.example.customrules
Bundle-Version: 1.0.0
Fragment-Host: ch.acanda.eclipse.pmd.core;bundle-version="1.4.1"
Bundle-RequiredExecutionEnvironment: JavaSE-1.7

You can choose your own values for the headers Bundle-Name, Bundle-SymbolicName and Bundle-Version. The value of the header Bundle-ManifestVersion must be 2. Fragment-Host must contain the symbolic name of the host bundle ch.acanda.eclipse.pmd.core and optionally the version of eclipse-pmd you have installed. Bundle-RequiredExecutionEnvironment specifies the minimum execution environment the plug-in fragment requires. Its value is JavaSE-1.7 if you compiled it with Java 7 or JavaSE-1.8 if you used Java 8.

Once you changed the manifest of your jar you can copy it into the folder dropins of your eclipse installation. Your plug-in fragment is installed when you start Eclipse.

Answer 2

Finally figured it out myself !

(I should've got it working in my previous attempt itself, but due to a stale custompmd.jar because of failed ANT task, it didn't work that time).

Step-by-step:

1. Copy the ch.acanda.eclipse.pmd.core_<blahblah#>.jar from plugins directory into a temp directory.
2. Open the JAR in temp directory using 7-Zip software
3. Add custompmd.jar into the lib directory.
4. Edit META-INF/MANIFEST.MF file, append this string ,lib/custompmd.jar at the end of Bundle-Classpath:
5. Close 7-Zip (and accept the Save dialog).
6. Take a backup of the existing /plugins/ch.acanda.eclipse.pmd.core_<blahblah#>.jar and replace it with this temp jar.
7. Exit Eclipse and Restart