Title: Default JDK for cross JDK project profiles with Maven
Date: 2009-04-25
Lang: en

In my [previous blog post about Cross JDK project files with Maven](|filename|./cross-jdk-project-files-continued.md) 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](http://n2.nabble.com/org.apache.maven.plugins%3Amaven-eclipse-plugin%3A2.7-SNAPSHOT-ignores--maven-compiler-plugin-tp2689287p2689425.html) 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:

    :::xml
    <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).