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Can logger instance be static in multithreaded app?

Jack Tyer

Joined: Feb 17, 2011
Posts: 1
In a multithreaded application, can a logger (log4j) instance be static?

I have a static method that uses logging messages, something like the code below

Public Foo{

private static Logger logger = Logger.getLogger(Foo.class.getName());

public static boolean doSomething(Boo boo){ something with boo.....

logger.debug("something happened");

return true/false;

If I want the method to be static, I have to declare my logger instance to be static. Since static variables are 1 per class and will be shared among all the instances of the class Foo, can we declare the logger instance as static?. If all the instances of class Foo try to log the messages to the one logger instance, it may cause problems, like dirty writes, am I correct? I don't want to make the method or logger instance synchronized, that's gonna hit the performance big time. In such case how to deal with the static methods that need logging in multithreaded app.

Appreciate much your replies.


Jesper de Jong
Java Cowboy
Saloon Keeper

Joined: Aug 16, 2005
Posts: 15081

Welcome to the Ranch.

What you're really asking is if a Log4J Logger is thread-safe. The Log4J FAQ answers this question:
Log4J FAQ wrote:
7. Is log4j thread-safe?

Yes, log4j is thread-safe. Log4j components are designed to be used in heavily multithreaded systems.

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Saifuddin Merchant
Ranch Hand

Joined: Feb 08, 2009
Posts: 607

Yes log4J synchronizes writes (unless you use an Async appender). Watch out could be a performance problem in really big systems!

Cheers - Sam.
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