Description

在下载 Maven包，配置了环境变量之后，在命令行执行 mvn -version(or -v) 报错：

 1 Exception in thread "main" java.lang.UnsupportedClassVersionError: org/apache/ma
 2 ven/cli/MavenCli : Unsupported major.minor version 51.0
 3         at java.lang.ClassLoader.defineClass1(Native Method)
 4         at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
 5         at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
 6         at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:14
 7 1)
 8         at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
 9         at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
10         at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
11         at java.security.AccessController.doPrivileged(Native Method)
12         at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
13         at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClassFromSelf(Cl
14 assRealm.java:401)
15         at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(
16 SelfFirstStrategy.java:42)
17         at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadCl
18 ass(ClassRealm.java:271)
19         at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm
20 .java:254)
21         at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm
22 .java:239)
23         at org.codehaus.plexus.classworlds.launcher.Launcher.getMainClass(Launch
24 er.java:144)
25         at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Laun
26 cher.java:266)
27         at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.jav
28 a:229)
29         at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(La
30 uncher.java:415)
31         at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:
32 356)

Caused By

JAVA_HOME 中 jdk版本过低。虽然用的是 jdk6，但我下载的 maven 是最新的 3.3.9，把环境变量中的 JAVA_HOME 指向 jdk8，结果正常。

Solution

提高 JAVA_HOME 中 jdk 版本。