Configuring log4j2 and log4j using a single log4j2 xml file

24
votes

I've migrated my application to log4j 2, and I've configured it via log4j2.xml

However, some of the libraries I'm using depend on log4j 1. If I run the application using: 

-Dlog4j.configurationFile=path/to/log4j2.xml

log4j 1 complains about not finding a configuration file. I'm using the log4j 1.x bridge provided by log4j 2, log4j-1.2-api-2.0-rc1.jar. Is it possible to configure both using a single log4j2.xml?

An alternative I've tried is configuring both log4j and log4j2 together: 

-Dlog4j.configurationFile=path/to/log4j2.xml -Dlog4j.configuration=path/to/log4j.xml

My concern is fragmentation of my logging configuration files and output. I'm also concerned about possible conflicts between log4j.xml and log4j2.xml. e.g. the logfile error.log is configured to use a FileAppender in log4j 1 and a RollingFileAppender in log4j 2.

Any advice?

[note]

This is the error I'm seeing:

log4j:WARN No appenders could be found for logger (org.apache.activemq.util.ThreadPoolUtils).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.

The version of log4j 2 I'm using is log4j 2.0 rc1.

[answer]

Seems like activemq-5.8.0.jar was bundled with log4j 1. The solution was simply to load the log4j 1.x bridge before activemq.

2
javalogginglog4jlog4j2

2 Answers

38
votes

I would recommend using the log4j-1.2 adapter that is included in the log4j2 distribution. That way, any libraries coded to the log4j-1.2 API will work with log4j2 without any code changes.

Your classpath should include:

  • log4j-api-2.6.1.jar
  • log4j-core-2.6.1.jar
  • log4j-1.2-api-2.6.1.jar
  • log4j2.xml

Your classpath should not include:

  • log4j-1.2.x.jar
  • log4j.properties or log4j.xml (these will be ignored by log4j2 anyway)

See also http://logging.apache.org/log4j/2.x/faq.html#which_jars

2
votes

In a maven project using log4j2, it is possible to exclude log4j from modules that use it, in the pom, in order to enable log4j2 to take over:

<dependencies>
    <dependency>
        <groupId>commons-configuration</groupId>
        <artifactId>commons-configuration</artifactId>
        <version>1.4</version>
        <!--force usage of log4j2-->
        <exclusions>
            <exclusion>
                <groupId>log4j</groupId>
                <artifactId>log4j</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>2.3</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>2.3</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-1.2-api</artifactId>
        <version>2.3</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-web</artifactId>
        <version>2.3</version>
    </dependency>
</dependencies>

More info about that in the log4j FAQ