Getting info about invoking class

Question

Hello everybody. Is it possible to get information about class that invoking the other one?

class Bar{
    public Bar{}

    public String getInvokingClassInfo(){
        return "...";
    }
}

class Foo{
    public Foo(){
       Bar bar = new Bar();
       System.out.println("Invoking class is: "+bar.getInvokingClassInfo());
    }
}

How to get in the place:

System.out.println(bar.getInvokingClassInfo());

info about class that invoking (Foo) this one (Bar):

Invoking class: Foo

Answer 1

 StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
 String callerClassName = stackTrace[index].getClassName();

This is getting the stacktrace for the current thread. As noted in the comments, there are implementation differences, so if you fear such, you can implement something like this:

• loop through the StackTraceElement array (using a counter variable declared outside the loop)
• whenever you encounter the current class name and the current method, break
• get the next element of the array - it will be the invoker. (that's what index stands for in the above code)
• if the above doesn't provide relevant information you can always fall back to new Exception().getStackTrace()

Answer 2

The best (though contorted and ugly) solution I could think of would be to throw an exception inside Bar and catch it right away, then extract the caller info from its stack trace.

Update based on others' comments: you don't even need to throw and catch the exception, new Exception().getStackTrace() will do the trick.

Answer 3

The most robust way I can imagine is to pass "this" as an argument to B from inside A. Then B can have a look at the object, and print out its class.

Everything that fiddles with stack traces relies on things which are not guaranteed to work. The "pass-this" approach will.