Example For maven-compiler-plugin

1. Compiling Sources Using A Different JDK

The compilerVersion parameter can be used to specify the version of the compiler that the plugin will use. However, you also need to set fork to true for this to work. For example:

<project>
  [...]
  <build>
    [...]
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.3</version>
        <configuration>
          <verbose>true</verbose>
          <fork>true</fork>
          <executable><!-- path-to-javac --></executable>
          <compilerVersion>1.3</compilerVersion>
        </configuration>
      </plugin>
    </plugins>
    [...]
  </build>
  [...]
</project>

To avoid hard-coding a filesystem path for the executable, you can use a property. For example:

<executable>${JAVA_1_4_HOME}/bin/javac</executable>

Each developer then defines this property in settings.xml, or sets an environment variable, so that the build remains portable.

<settings>
  [...]
  <profiles>
    [...]
    <profile>
      <id>compiler</id>
        <properties>
          <JAVA_1_4_HOME>C:\Program Files\Java\j2sdk1.4.2_09</JAVA_1_4_HOME>
        </properties>
    </profile>
  </profiles>
  [...]
  <activeProfiles>
    <activeProfile>compiler</activeProfile>
  </activeProfiles>
</settings>

2. Setting the -source and -target of the Java Compiler

Sometimes when you may need to compile a certain project to a different version than what you are currently using. The javac can accept such command using -source and -target. The Compiler Plugin can also be configured to provide these options during compilation.

For example, if you want to enable assertions (-source 1.4) and also want the compiled classes to be compatible with JVM 1.4 (-target 1.4), you can then put:

<project>
  [...]
  <build>
    [...]
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.3</version>
        <configuration>
          <source>1.4</source>
          <target>1.4</target>
        </configuration>
      </plugin>
    </plugins>
    [...]
  </build>
  [...]
</project>

Note: Merely setting the target option does not guarantee that your code actually runs on a JRE with the specified version. The pitfall is unintended usage of APIs that only exist in later JREs which would make your code fail at runtime with a linkage error. To avoid this issue, you can either configure the compiler's boot classpath to match the target JRE or use the Animal Sniffer Maven Plugin to verify your code doesn't use unintended APIs.

3. Compile Using Memory Allocation Enhancements

The Compiler Plugin accepts configurations for meminitial and maxmem. You can follow the example below to set the initial memory size to 128MB and the maximum memory usage to 512MB:

<project>
  [...]
  <build>
    [...]
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.3</version>
        <configuration>
          <fork>true</fork>
          <meminitial>128m</meminitial>
          <maxmem>512m</maxmem>
        </configuration>
      </plugin>
    </plugins>
    [...]
  </build>
  [...]
</project>

4. Pass Compiler Arguments

Sometimes, you need to pass other compiler arguments that are not handled by the Compiler Plugin itself but is supported by the compilerId selected. For such arguments, use the Compiler Plugin's compilerArgs parameter The following example passes compiler arguments to the javac compiler:

<project>
  [...]
  <build>
    [...]
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.3</version>
        <compilerArgs>
            <arg>-verbose</arg>
            <arg>-Xlint:all,-options,-path</arg>
          </compilerArgs>
      </plugin>
    </plugins>
    [...]
  </build>
  [...]
</project>