Printing the “source” class in a log statement with a log4j wrapper

Question

My application has a homebrew logging class that I\'m migrating to using log4j under the covers. However, since I\'m using the homebrew class to pass the rest of the applica

Answer 1

In Log4J API about Logger.log(String callerFQCN, Priority level, Object message, Throwable t):

Parameters:

• callerFQCN - The wrapper class' fully qualified class name.
• level - The level of the logging request.
• message - The message of the logging request.
• t - The throwable of the logging request, may be null.

See: Log4J API.

Quite weird I know, argument is called "callerFQCN" which seams to be the caller object class, BUT (muajaja!) it's actually the "wrapper" class (ex MyClass.class.getName()).

Actually, the caller is get by the Throwable argument I think. Not sure, haven't checked the implementation.

As you leave Throwable argument null, I think something like this must be happening below:

StackTraceElement[] stack = (new Throwable()).getStackTrace();
String caller = stack[something, meaby 1].getClassName();

If you want to create a Logger wrapper you need to do something like this:

public static void myWarn(String message) {
    myLogger.log(MyWrapper.class.getName(), message, Level.WARN, null);
}

This work without problem as a wrapper.

Or, if you absolutely need to maintain the interface you show below, do something like this:

// Warning: Pseudocode
public static void myWarn(Object source, String message) {
    String sourceClass = source.class.GetName();
    StackTraceElement[] stack = (new Throwable()).getStackTrace();
    stack[1, or meaby 2... or 0?] = new whatever(sourceClass);
    myLogger.log(MyWrapper.class.getName(), message, Level.WARN, myStack);
}

Hope this helps.