How to write caller location information in a log file using Java, without hurting performance?

How can I write caller location information (Java source file and line), in a log file using Java and log4j, but without hurting performance? log4j allow yo开发者_JS百科u to write such information in the log file, but it uses the stack trace to get that it information, every time a log statement is issued, what causes performance degradation. I'm looking for a performance friendly alternative, like getting the location information at compile time instead at runtime. It is possible to use annotations to accomplish that? Or maybe some other technique?

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How about making it part of the build process to replace certain placeholders, like $filename$ and $linenumber$ in this snippet.

logger.info("The original message... $filename$ $linenumber$");

To replace the filename, it may suffice to have keyword substitution with your revision control system. Disclaimer: this is just from the top of my head, I never tried it myself.

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I agree with Rob that it is generally unnecessary. Usually there's some distinct string in a log message, searching for it will get to the source. With a good IDE this is really fast.

Now, given the question as is, this is a possible solution:

Class Foo
    void bar()
        new Logger(){} . warn("blah");

for each log action at runtime, a new object is created - that's not a problem.

for each line of source containing such log statement, a new class is created. that can be too many.

here's how the magic works:

abstract public class Logger
    static Map<Class, String> sourceInfo = new ...
    public Logger()
        Class thisClass = this.getClass();
        String info = sourceInfo.get(thisClass);
        if(info==null)
             info = ... // init from stack trace
             sourceInfo.put(thisClass,info)
        this.info = info

     public void warn(msg)
        log(WARN, this.info,msg)