Jetty 9.0启动报错org/apache/nutch/crawl/Crawl3 : Unsupported major.minor version 51.

java -jar start.jar

报如下错误：

ava.lang.UnsupportedClassVersionError: org/apache/nutch/crawl/Crawl3 : Unsupported major.minor version 51.0
 at java.lang.ClassLoader.defineClass1(Native Method)
 at java.lang.ClassLoader.defineClassCond(Unknown Source)
 at java.lang.ClassLoader.defineClass(Unknown Source)
 at java.security.SecureClassLoader.defineClass(Unknown Source)
 at java.net.URLClassLoader.defineClass(Unknown Source)
 at java.net.URLClassLoader.access$000(Unknown Source)
 at java.net.URLClassLoader$1.run(Unknown Source)
 at java.security.AccessController.doPrivileged(Native Method)
 at java.net.URLClassLoader.findClass(Unknown Source)
 at java.lang.ClassLoader.loadClass(Unknown Source)
 at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
 at java.lang.ClassLoader.loadClass(Unknown Source)
Exception in thread “main”

 把jdk改为1.7版本，可以成功启动