Send/redirect/route java.util.logging.Logger (JUL) to Logback using SLF4J?

Question

Is it possible to have a typical call to java.util.logging.Logger and have it route to Logback using SLF4J? This would be nice since I wouldn't have to refactor the old jul code line by line.

EG, say we have this line:

private static Logger logger = Logger.getLogger(MahClass.class.getName());
//...
logger.info("blah blah blah");

It would be nice to configure this to call through SLF4J.

Answer 1

It's very easy and not a performance issue anymore.

There are two ways documented in the SLF4J manual. There are also precise examples in the Javadocs

Add jul-to-slf4j.jar to your classpath. Or through maven dependency:

<dependency>
    <groupId>org.slf4j</groupId>
     <artifactId>jul-to-slf4j</artifactId>
    <version>1.7.0</version>
</dependency>

If you don't have logging.properties (for java.util.logging), add this to your bootstrap code:

SLF4JBridgeHandler.removeHandlersForRootLogger();
SLF4JBridgeHandler.install();

If you have logging.properties (and want to keep it), add this to it:

handlers = org.slf4j.bridge.SLF4JBridgeHandler

In order to avoid performance penalty, add this contextListener to logback.xml (as of logback version 0.9.25):

<?xml version="1.0" encoding="UTF-8"?>
<configuration>

    <contextListener class="ch.qos.logback.classic.jul.LevelChangePropagator">
        <!-- reset all previous level configurations of all j.u.l. loggers -->
        <resetJUL>true</resetJUL>
    </contextListener> 

    ...

</configuration>