Default JDK for cross JDK project profiles with Maven

In my previous blog post about Cross JDK project files with Maven I described a way to generate a custom JDK name into the Eclipse project files using the maven-eclipse-plugin.

That approach still had one shortcoming: you would either have to rename your JDK to match the default configured in the POM or you would have to give the JDK name on the commandline. Now I stumbled over a good tip on the maven user’s list that allows you to configure a sensible, cross platform default for the JDK.

In short, the trick is not to use a concrete name of a JDK but to specify the name of a Java runtime environment. Eclipse automatically tries to match any configured JDK to an internal list of runtime environments.

So if you put the following into your pom:

<properties>
    <vmtype>org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType</vmtype>
    <jdk5Name>J2SE-1.5</jdk5Name>
</properties>
...
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-eclipse-plugin</artifactId>
    <version>2.5.1</version>
    <configuration>
        <downloadSources>true</downloadSources>
        <classpathContainers>
            <classpathContainer>org.eclipse.jdt.launching.JRE_CONTAINER/${vmtype}/${jdk5Name}</classpathContainer>
        </classpathContainers>
    </configuration>
</plugin>

Eclipse will assign a JDK5 runtime environment to the project (if it has a matching one configured, of course).