Simple example of a custom annotation for log

Question

Please help me write me my custom annotations. I like to use them to provide log ,security etc . I did not find articles where I can write my annotation to change the behaviour. Suppoe I decare annotation on a method , I want jvm to call code in my annotation where I can control the behaviour of the method similar to aop stuff ,
here is what i need
MyClass {
  @MyCustomAnnotation
   void myMethod(){
}now I want MyCustomAnnotation to log that this method is begin called can I do this ?

Answer 1

I can think of only one way to do something like this, and it's messy:
Let's say your code looks like this:
public class MyClass
    @MyLogging
    public void myMethod(String arg)
}Have your @MyLogging annotation processing generate a new Class source that extends your original class and overrides the methods that you've annotated with code that looks something like this:
public class MyClassGenerated extends MyClass
   Log log = ... // create a logger
    @Override
    public void myMethod(String arg)
        log.info("myMethod called");
        super.myMethod(arg);
}Now you'll have to change your code to use MyClassGenerated instead of MyClass, which presents its own problems... you may be able to add in some kind of factory mechanism or something to make that work easier.