Building and Installing Log4j

The information below is for developers who want to modify Log4j or contribute to Log4j. If your goal is to add logging to your application you don’t need to build from the source code, you can download the pre-built binaries instead.

Log4j 2 is hosted in the Apache Software Foundation’s Git repository. Details on obtaining the most current source code can be found at Log4j Source Repository. The source from the latest release may be obtained by downloading it using the instructions at Log4j Downloads.

Log4j 2.x uses Maven 3 as its build tool. Log4j 2.x uses the Java 9 compiler in addition to the Java version installed in the path. This is accomplished by using Maven’s toolchains support. Log4j 2 provides sample toolchains XML files in the root folder. This may be used by modifying it and installing the file as toolchains.xml in the .m2 folder or by using the following when invoking Maven.

[Macintosh] -t ./toolchains-sample-mac.xml 
[Windows] -t ./toolchains-sample-win.xml 
[Linux] -t ./toolchains-sample-linux.xml 

To build and install Log4j in your local Maven cache, from the parent project directory, and using Java 7 or 8, run: mvn install

Note that if your /etc/hosts file does not include an entry for your computer’s hostname, then many unit tests may execute slowly due to DNS lookups to translate your hostname to an IP address in InetAddress::getLocalHost. To remedy this, you can execute the following:

printf '127.0.0.1 %s\n::1 %s\n' `hostname` `hostname` | sudo tee -a /etc/hosts

Then to build the full site, you must use a local staging directory:

mvn site
[Windows] mvn site:stage-deploy -DstagingSiteURL=file:///%HOME%/log4j
[Unix] mvn site:stage-deploy -DstagingSiteURL=file:///$HOME/log4j

To rebuild only what’s changed and execute the tests, run: mvn test

To rebuild from scratch, add “clean”, for example: mvn clean test