LoggerInterceptor for final method not working about byte-buddy

[raphw]

Are you subclassing a class with a final method? It is not possible to override such a method, you would need to use a Java agent or some other sort of class redefinition. I once blogged about this: http://mydailyjava.blogspot.no/2015/01/make-agents-not-frameworks.html

[Pasupathi-Rajamanickam]

I don't do such. Have look at my code pls.

public class Hello {
  public final String sayHello() {
    return "hello";
  }
}

That's it. I cannot use byte-buddy to log this 'sayHello' function?

[raphw]

Can you post a running example that uses Byte Buddy to instrument your class?

[Pasupathi-Rajamanickam]

Ya here is that. I have these 3 classes in 3 different files.

Main class - To create bytebuddy class and run it.

public class ByteEx {

  public static void main(String[] d) throws Exception{
    new ByteEx().loadclassDD();
  }

  public void loadclassDD() throws Exception{
    Hello loggingDatabase = new ByteBuddy() 
      .subclass(Hello.class)
      .method(named("sayHello")).intercept(MethodDelegation.to(LoggerInterceptor.class))
      .make()
      .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER)
      .getLoaded()
      .newInstance();
    System.out.println(loggingDatabase.sayHello());
  }
}

Logger class. - This will return upper case of original string data if my method is called.

public class LoggerInterceptor {
    public static String log(@SuperCall Callable<String> zuper)
        throws Exception {
    System.out.println("Calling database");
    try {
      return  zuper.call().toUpperCase();
    } finally {
      System.out.println("Returned from database");
    }
  }
}

Target class which have a method will return lower case data

public class Hello {
  public final String sayHello() {
    return "hello";
  }
}

[raphw]

Hi, as I said, it is not possible to *subclass and override a final method. Not with Byte Buddy and not on the Java platform in general. You would need to use a Java agent and redefine the class as I described in the linked blog posting.

[Pasupathi-Rajamanickam]

You mean to say I should remove the final from the class?
I've seen the blog, but still this cannot be achieved for final method right?

[raphw]

No, it is simply not possible to override a final method, any (generated) class that would override such a method would be rejected with a verification error by the Java virtual machine. For this reason, Byte Buddy does not even consider overriding such a class.

[Pasupathi-Rajamanickam]

OK. Ya I think you are correct. I tried couple of interceptor, but no luck. OK. Thanks for the response. Good luck for your project. It's really awesome and simple.

[raphw]

Thanks!