Question

The Java OpenGL GL interface contains about 2000 methods, for debugging purposes I would like to wrap an instance and delegate calls to it while doing some logging. The logging code can be pushed to the same method in each case, so the task of writing out the method implementations looks like it could be automated. An example of what I am trying to do:

import javax.media.opengl.GL;

public class GLErrorLogger implements GL {
  private final GL backing;

  public GLErrorLogger(GL delegateToMe) {
    backing = delegateToMe;
  }

  private void checkErrorCode() {
    // Log frame and thread details depending on gl state
  }

  /**
   * Example of a method
   */
  @Override
  public int glGenLists(int arg0) {
    checkErrorCode();
    int retVal = backing.glGenLists(arg0);
    checkErrorCode();
    return retVal;
  }

  // rest of methods here...
}

In other words copy the method name and parameters (minus their types) into a call on the backing object, surround with calls to the logging method, and if there is a return type then assign the result to a variable of this type and return it at the end of the method.

I looked at creating a one shot eclipse code template to autogenerate the methods, but there wasn’t an immediately obvious way to do pattern matching on the return type. Can anyone suggest a way to do this in Eclipse or any of its code generation tools to save me pulling out the regex toolkit?

Answer 1

You might want to use an Aspect to create the necessary bytecode for you instead of producing all the source code. Take a look at the Traceing Aspect example here: Traceing Aspect Example.

As an Alternative, you can create a Java Dynamic Proxy, if you do not want to use AspectJ as Thrid party Library. Please refer to Dynamic Proxy Tutorial