Use of ClassLoader for resolve incompatible dependencies ?

Question

Hi,
I'm relatively new to Java but I have a problem that I think need some expertise I dont have yet. I'm developing a module in an application that uses an API from a third party. My module and the application that contains it depend on commons-httpclient-3.1 but the third party API depends on commons-httpclient-2.0.2. The third party API cannot be updated to be compatible with the last version. I've been looking around and found ClassLoader may help me, but I'm not familiar with its use.
What I assume is that I can have a class in my code where all access to the third party API will be done and this class and all other classes from the API will be loaded with a class loader that will have a complete set of jars dependencies (including httpclient-2.0.2) so the main application and this "module" will not interfere each other and have their dependencies solved in the proper way. I'm in the correct path to solve my problem ? Does anybody have any ideas to help me ?
Thanks in advance,
Regards, Dismer

Answer 1

This is the code I implemented to solve my problem. I created the third_party_stub.jar where I have a class that make all calls to third_party.jar
Hope it will be useful to someone.
Any comments are very welcome !
Greetings, Dismer
import java.net.URLClassLoader;
import java.net.URL;
import java.net.MalformedURLException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class Main
       public static void main( String[] args )
          try
               URL URLs[] =
                    new URL( "jar:file:/opt/bob/instances/es/lib/third_party.jar!/" ),
                    new URL( "jar:file:/opt/bob/instances/es/lib/third_party_stub.jar!/" ),
                    new URL( "jar:file:/opt/bob/instances/es/lib/commons-httpclient-2.0.2.jar!/" )
               URLClassLoader loader = new URLClassLoader( URLs, null );
               Class stub_class = loader.loadClass( "com.thirdparty.Stub" );
               Method stub_method = stub_class.getDeclaredMethod( "Test", new Class[] { String.class } );
               Object stub_object = stub_class.newInstance();
               System.out.println( stub_method.invoke( stub_object, new Object[] { "test parameter" } ) );
          catch ( MalformedURLException e )
               System.out.println( "MalformedURLException " + e.toString() );
          catch (IllegalAccessException e)
               System.out.println( "IllegalAccessException " + e.toString() );
          catch (InvocationTargetException e)
               System.out.println( "InvocationTargetException " + e.toString() );
               System.out.println( "InvocationTargetException " + e.getTargetException().toString() );
          catch (ClassNotFoundException e)
               System.out.println( "ClassNotFoundException " + e.toString() );
          catch (InstantiationException e)
               System.out.println( "InstantiationException " + e.toString() );
          catch (SecurityException e)
               System.out.println( "SecurityException " + e.toString() );
          catch (NoSuchMethodException e)
               System.out.println( "NoSuchMethodException " + e.toString() );
}