Maven eclipse插件使用Eclipse JRE而不是JAVA_HOME

Question

I upgraded to maven 3 . My projects are built using jdk6, so eclipse JRE points to java 6 home. It appears that maven 3 requires java 7. My JAVA_HOME points to java 7, but Maven plugin apparently uses JRE 6 (Eclipse JRE), and throws this exception when run from eclipse:

Exception in thread "main" java.lang.UnsupportedClassVersionError: org/apache/maven/cli/MavenCli : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClassFromSelf(ClassRealm.java:401)
at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:42)
at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadClass(ClassRealm.java:271)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:254)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:239)
at org.codehaus.plexus.classworlds.launcher.Launcher.getMainClass(Launcher.java:144)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:266)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356) 

How can I let m2eclipse use java7 (which is my JAVA_HOME)?

Note that standalone maven works properly, but it's easier to run it from eclipse.

Answer 1

set M2_HOME to you maven home, set JAVA_HOME, then set you path so at the beginning is

   Path=%JAVA_HOME%/bin;%M2_HOME%/bin

If you're on windows this is set by start->right click on computer, properties->advanced system settings->environment variables.

You also need to change you eclipse to use the java 1.7 jdk. That should take care of things, you can set the compile level in your eclipse/maven project to 1.6.

Answer 2

I were facing same issue with eclipse. Adding below plugin to plugins list and rebuild project using Alt+F5 solved my problem. Hope it will solve yours as well :

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.5.1</version>
    <configuration>
        <debug>true</debug>
        <verbose>true</verbose>
        <source>1.7</source>
        <target>1.7</target>
        <fork>true</fork>
    </configuration>
</plugin>

After rebuild eclipse will automatically select JRE1.7 if you have JRE1.7 configured in eclipse preferences.