| ------ |
| Compiling Sources Using A Different JDK |
| ------ |
| Edwin Punzalan |
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| 2006-07-05 |
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| |
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| |
| Compiling Sources Using A Different JDK |
| |
| * Using Maven Toolchains |
| |
| The preferable way to use a different JDK is to use the toolchains mechanism. During the build of a project, Maven, |
| without toolchains, will use the JDK to perform various steps, like compiling the Java sources, generate the Javadoc, |
| run unit tests or sign JARs. Each of those plugins need a tool of the JDK to operate: <<<javac>>>, <<<javadoc>>>, |
| <<<jarsigner>>>, etc. A toolchain is a way to specify the path to the JDK to use for all of those plugins in a |
| centralized manner, independent from the one running Maven itself. |
| |
| To set this up, refer to the {{{/guides/mini/guide-using-toolchains.html}Guide to Using Toolchains}}, which makes use |
| of the {{{/plugins/maven-toolchains-plugin/}Maven Toolchains Plugin}}. |
| |
| With the maven-toolchains-plugin you configure 1 default JDK toolchain for all related maven-plugins. |
| Since maven-compiler-plugin 3.6.0 when using with Maven 3.3.1+ it is also possible to give the plugin its own |
| toolchain, which can be useful in case of different JDK calls per execution block (e.g. the test sources require a |
| different compiler compared to the main sources). |
| |
| * Configuring the Compiler Plugin |
| |
| Outside of a toolchain, it is still possible to tell the Compiler Plugin the specific JDK to use during compilation. |
| Note that such configuration will be specific to this plugin, and will not affect others. |
| |
| 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>${project.version}</version> |
| <configuration> |
| <verbose>true</verbose> |
| <fork>true</fork> |
| <executable><!-- path-to-javac --></executable> |
| <compilerVersion>1.3</compilerVersion> |
| </configuration> |
| </plugin> |
| </plugins> |
| [...] |
| </build> |
| [...] |
| </project> |
| +------- |
| |
| To avoid hard-coding a filesystem path for the executable, you can use a |
| property. For example: |
| |
| +------- |
| <executable>${JAVA_1_4_HOME}/bin/javac</executable> |
| +------- |
| |
| Each developer then defines this property in |
| {{{http://maven.apache.org/ref/current/maven-settings/settings.html}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> |
| +------- |
| |
| If you build with a different JDK, you may want to |
| {{{http://maven.apache.org/plugins/maven-jar-plugin/examples/manifest-customization.html} |
| customize}} the jar file manifest. |