How to Control Which Java Version Maven Uses When Multiple Versions Exist?

Specify Java Version for Maven

When multiple Java versions coexist on a system, it can be challenging to ensure that Maven uses the appropriate version for specific projects. This article addresses how to configure Maven to utilize a specific Java installation.

Problem Statement

The user has two Java versions installed: 1.6 and 1.7. While both versions are required for different projects, Maven is currently using Java 1.6, even though it should be using Java 1.7.

Solution

Maven locates the Java version to use based on the JAVA_HOME environment variable. Since the user cannot modify this variable in the configuration, there are two options:

1. Set JAVA_HOME Parameter Before Starting Maven

This method allows you to set JAVA_HOME to the desired Java version before running Maven and then reverting it afterwards.

2. Modify Maven Script

Open the relevant Maven script (mvn for non-Windows, mvn.bat or mvn.cmd for Windows) and explicitly set the Java version.

Example (Maven Script Modification)

#!/bin/bash

JAVA_HOME="/path/to/java1.7.x"

exec java $JAVA_OPTS -classpath "$M2_HOME/lib/plexus-classworlds-2.6.0.jar:$M2_HOME/lib/plexus-component-annotations-1.5.5.jar" \
  -Dmaven.home="$M2_HOME" -Dmaven.multiModuleProjectDirectory="$M2_HOME" \
  -jar "$M2_HOME/bin/mvn.jar" "$@"

Remember to replace "/path/to/java1.7.x" with the actual path to your Java 1.7 installation.

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