Configuring log4j2 and log4j using a single log4j2 xml file

Question

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 applicatio

Answer 1

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

Answer 2

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