修改现有的Eclipse插件并正确安装它

I downloaded the source code for the EMF based UML2 Plugin and changed a class in the org.eclipse.uml2.uml.edit project to remove special characters when returning string representations. Now when I export the projects and place the jar files either in the dropins directory or replace my current uml2 plugin jar files in plugins directory, The UML files are no longer recognized, in short my modified plugin does not install correctly (no error is thrown and I can see the files being picked up under Plugins->Target Platform) .I downloaded the source code for the EMF based