Comments on: Interesting trick to finding Java caller

By: Brian

Brian — Thu, 01 Jan 1970 00:00:00 +0000

You can also just ask the current thread for its stack trace rather than creating the exception.

By: James

James — Thu, 01 Jan 1970 00:00:00 +0000

This is cool. Now…how do you get the calling Object?

By: Leo

Leo — Thu, 01 Jan 1970 00:00:00 +0000

It’s a Throwable, but it’s also probably getting the stack trace from the current Thread, so that’s a good idea.

Also attainable from the StackTraceElement is the method name in case you want to know who’s calling you. It’s useful if you want supergeneric recursion or callback by convention.

By: Andy

Andy — Thu, 01 Jan 1970 00:00:00 +0000

It used to be that Thread.getStackTrace accompished its task by doing the throw too. I suspect things haven’t changed.

Nicely done.

By: anjan bacchu

anjan bacchu — Thu, 01 Jan 1970 00:00:00 +0000

hi there,

I didn’t understand how getLog() gets used in info() call. Sorry for being dense — can you explain with lil more details — probably there are others who might not get it.

I’ve been using the new Throwable() trick for a long time but this one I don’t grok.

BR,
~A

By: Warner Onstine

Warner Onstine — Thu, 01 Jan 1970 00:00:00 +0000

@anjun
Here’s how `info()` works

public static final void info(String pattern, Object … objs) {
getLog().debug(getMessage(pattern, objs));
}

Which you can do a static import on:

import static FormattedLogging.info

and then directly reference in your class. This way you no longer have to do `LogFactory.getLog(MyClass.class)`, this will do it for you automatically.

@Andy
The credit belongs all to Leo .

By: Casper

Casper — Thu, 01 Jan 1970 00:00:00 +0000

I’ve used this numerous times as a means to achieve IOC during DBUnit tests, inject test data into the database by tracing the class and test method and load data from a file named the same.

By: Gagan

Gagan — Thu, 01 Jan 1970 00:00:00 +0000

Stack trace creation is a heavy operation isn’t it, i wonder about the performance aspects of this?

By: Arnaud

Arnaud — Thu, 01 Jan 1970 00:00:00 +0000

@Gagan it must be pretty costly also I never mesure the performance it. It would probably be usefull to cache the Logger in a way or another.

I use the Exception trick to store when a connection was open to detect not close exception years ago – the state was capture in the finalizer, which print the stack trace to indicate where the leak came from -.

By: Notafan

Notafan — Thu, 01 Jan 1970 00:00:00 +0000

You’ve really got to be asking yourself why you are writing ugly hacks like this. It’s expensive and clumsy. What if you want to use AOP to intercept calls?

Seems ok for test code but if it makes it to your production code you’ve got to question your design.