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During the Spring Workshop, Rod Johnson started a brief discussion on how to find out in a Java Class who invoked the method currently being executed. The best trick: create a new Throwable and inspect the stacktrace. In Java 1.3 you had to use the printstackTrace() method and parse the String, in Java 1.4 there is the StackTraceElement[] that you can inspect. A simple utility class that informs any caller about his own caller could look like this:
public static String whoCalledMe()
{
Throwable t = new Throwable();
return t.getStackTrace()[2].toString();
}or:
public static Class whoCalledMe()
{
Throwable t = new Throwable();
return t.getStackTrace()[2].getClass(); // that is: Class, not Object!
}example code:
/*
* Created on Jun 10, 2005
*
*/
package nl.amis.util;
/**
* @author Lucas
*
*/
public class CallStackUtils {
public static String whoCalledMe()
{
Throwable t = new Throwable();
return t.getStackTrace()[2].toString();
}
public String getCall() {
return whoCalledMe();
}
public String inBetween() {
return getCall();
}
public static void main(String[] args) {
CallStackUtils call = new CallStackUtils();
System.out.println(call.inBetween());
}
}The output of running main is: nl.amis.util.CallStackUtils.inBetween(CallStackUtils.java:24)
Methods on StackTraceElement include: isNativeMethod() getLineNumber() getClass() getMethodName() getFileName() getClassName()
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Hi!
I blogged about this more than 2 years ago, and was then told by someone that it was an old well known trick. I guess there’s always someone else ahead…
http://www.jroller.com/page/matsh/20030221#how_to_do_c_friends
In Java 1.5 you don’t need to create Throwable anymore (expensive operation), use Thread.getStackTrace() instead.