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Setting the -source and -target of the Java Compiler

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Edwin Punzalan

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2006-07-05

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Setting the <<<-source>>> and <<<-target>>> of the Java Compiler

(If you're are using version <<<3.13.0>>> or newer of the Compiler Plugin, use the recommended

{{{../examples/set-compiler-release.html}<<<maven.compiler.release>>> property}}.)

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.

You have to set the version following {{{https://openjdk.org/jeps/223}Java's new Version-String Scheme (JEP 223)}}}.

For example, if you want to use the Java 8 language features and also want the compiled classes to be compatible

with JVM 8 (former 1.8) you can either add the two following properties, which are the default property names

for the plugin parameters:

+-----

<project>

[...]

<properties>

<maven.compiler.source>8</maven.compiler.source>

<maven.compiler.target>8</maven.compiler.target>

</properties>

[...]

</project>

+-----

or configure the plugin directly:

+-----

<project>

[...]

<build>

[...]

<plugins>

<plugin>

<groupId>org.apache.maven.plugins</groupId>

<artifactId>maven-compiler-plugin</artifactId>

<version>${project.version}</version>

<configuration>

<source>8</source>

<target>8</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

{{{http://www.mojohaus.org/animal-sniffer/animal-sniffer-maven-plugin/}Animal Sniffer Maven Plugin}}

to verify your code doesn't use unintended APIs, or better yet use the

{{{../examples/set-compiler-release.html}<<<release>>> option supported since JDK 9}}.

Since plugin version <<<3.13.0>>> you can use the <<<release>>> property also on JDK 8.

The compiler plugin will convert it to <<<source>>> and <<<target>>> automatically.

In the same way, setting the <<<source>>> option does not guarantee that your code actually compiles on a JDK with

the specified version. To compile your code with a specific JDK version, different than the one used to launch Maven,

refer to the {{{../examples/compile-using-different-jdk.html}Compile Using A Different JDK}} example.