How to ensure loading of classes of external jars when called from an eclipse plugin?

Question

Hi All,

I have developed an eclipse plugin which references an external jar present in a external installation directory. So I have added an entry to my bundle classpath as below:

Bundle-ClassPath: external:C:\mylib.jar

My class loads properly - and the plugin is able to detect a class MyClass present in this external lib.
However, the method a() - I am calling in the class MyClass is failing.

Method a() is as follows :

public void a()
{
  URL url = this.class.getClassLoader().getResource("META-INF/startup-jar ");
  ...
}

so the URL which is returned is that of the eclipse plugin directory C:\eclipse3.4\test and not of the physical location of the external jar which is C:\mylib.jar

This is causing method a() to fail. Now, my question is -
As I don't have the external jar copied to my plugin directory (it is only present on the plugin classpath)

how can I ensure the classloader gets the URL path of my external jar and not of my plugin directory?

Note : I cannot change the classloading mechanism in the external jar as it is a third party dependency and I have no control over the code. So please suggest a solution which would help me to load the external jar class correctly so I can get the correct URL.

Thanks a lot for your help - in advance

To explain a bit more on the problem I am facing :: My external jar is present inside the installation directory of my server installation.

When the class in my external jar calls the URL url = this.class.getClassLoader().getResource("startup-jar")

it returns the URL relative to the eclipse bundle path - Something like C:\eclipse3.4...

and this URL is used for getting the boot directory (installation directory of the server) .

So it should have returned a path which is relative to the server installation directory, but instead returns a path relative to the eclipse installation directory.

Because of this, I am not able to call any APIs on the server as the server installation directory which it tries to use is incorrect.

So I wanted to know what is the best way I can handle this, so that this method call returns the server installation dir and not eclipse bundle path.

Answer 1

Can't you wrap this 3rd party dependency with the correct OSGI metadata and install it as a plug-in/bundle? We did this for all 3rd-party dependencies, including problematic ones such as Hibernate and made them work.

If it's a popular open source library, you can probably find it with the OSGi metadata added at Spring's repository: www.springsource.com/repository/app

In general, I wouldn't recommend the pattern of referencing external JARs as you describe in your question.