Maven and Java version setting -- which solution is better?

Question

I have been searching for a solution to my Maven and Eclipse JRE version issue, where JRE 1.5 is being forced in the Eclipse project somehow even when I want different.

During my searches, I have noticed that there appear to be two different solutions to this. The first solution suggests using something like the snippet below

<build>
    <plugins>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
           <source>1.6</source>
           <target>1.6</target>
        </configuration>
    </plugin>
    </plugins>
</build>

The second solution suggests using just two properties:

<properties>
    <maven.compiler.source>1.6</maven.compiler.source>
    <maven.compiler.target>1.6</maven.compiler.target>
</properties>

Why are the two possible solutions and why do they differ?

Answer 1

There's a long way to specify it (by defining a <plugin> configuration in your pom file), which is the normal way to configure plugins, and there is a shorthand using a user property.

As you can find in the documentation.

The -source argument for the Java compiler. Default value is: 1.5.

User property is: maven.compiler.source.

If you only want to specify the source and target level, then there is no difference, but the <plugin> configuration also allows you to specify other configuration settings, restrict the versions of the compiler plugin, etc.

Answer 2

Many Maven plugins allow to use some properties to specify the parameters. The maven.compiler.source and maven.compiler.target properties are specified by the Maven Compiler Plugin.

See the "User Property" sections:

http://maven.apache.org/plugins/maven-compiler-plugin/compile-mojo.html#source

http://maven.apache.org/plugins/maven-compiler-plugin/compile-mojo.html#target

http://maven.apache.org/plugins/maven-compiler-plugin/compile-mojo.html