org/apache/maven/cli/MavenCli : Unsupported major.minor version 51.0

今天构建SSM项目时，将JDK由1.8降低至1.6，然后报错org/apache/maven/cli/MavenCli : Unsupported major.minor version 51.0。

1.错误信息

错误详细信息如下

"C:\Program Files\Java\jdk1.6.0_45\bin\java" -Dmaven.multiModuleProjectDirectory=C:\Users\hanchao\IdeaProjects\myssm "-Dmaven.home=C:\Program Files\JetBrains\IntelliJ IDEA 2017.3\plugins\maven\lib\maven3" "-Dclassworlds.conf=C:\Program Files\JetBrains\IntelliJ IDEA 2017.3\plugins\maven\lib\maven3\bin\m2.conf" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2017.3\lib\idea_rt.jar=55269:C:\Program Files\JetBrains\IntelliJ IDEA 2017.3\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\JetBrains\IntelliJ IDEA 2017.3\plugins\maven\lib\maven3\boot\plexus-classworlds-2.5.2.jar" org.codehaus.classworlds.Launcher -Didea.version=2017.3 clean tomcat7:run -e
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:631)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
    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)
    at org.codehaus.classworlds.Launcher.main(Launcher.java:47)

2.错误分析

通过mvn -v可知本人maven版本为3.3.9：

C:\Users\hanchao>mvn -v
Apache Maven 3.3.9 (bb52d8502b132ec0a5a3f4c09453c07478323dc5; 2015-11-11T00:41:47+08:00)
Maven home: D:\apache-maven-3.3.9
Java version: 1.8.0_131, vendor: Oracle Corporation
Java home: C:\Program Files\Java\jdk1.8.0_131\jre
Default locale: zh_CN, platform encoding: GBK
OS name: "windows 10", version: "10.0", arch: "amd64", family: "dos"

而major.minor version 51.0指的是JDK1.7。
报错原因：Maven 3.3.1+需要JDK 1.7及其以上的版本。

3.错误解决

任选其一：

1. 降低maven版本至3.3.1以下。
2. 升高项目JDK版本至1.7以上。