Jetty9.x的错误提示：
java.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"
解决问题
UnsupportedClassVersionError提示是jdk版本问题。
查找版本对应问题
http://blog.csdn.net/gao36951/article/details/45318315
1：jetty各个版本信息
| 9.3 | 2014 | Eclipse | 1.7 | HTTP/1.1, HTTP/2 RFC2616,javax.websocket, SPDY v3 | 3.1 | 2.3 | Experimental |
| 9.2 | 2014 | Eclipse | 1.7 | HTTP/1.1 RFC2616,javax.websocket, SPDY v3 | 3.1 | 2.3 | Stable |
| 8 | 2009-至今 | Eclipse/Codehaus | 1.6 | HTTP/1.1 RFC2616, WebSocket RFC 6455, SPDY v3 | 3.0 | 2.2 | Mature |
| 7 | 2008-至今 | Eclipse/Codehaus | 1.5 | HTTP/1.1 RFC2616, WebSocket RFC 6455, SPDY v3 | 2.5 | 2.1 | Mature |
| 6 | 2006-2010 | Codehaus | 1.4-1.5 | HTTP/1.1 RFC2616 | 2.5 | 2.0 | Venerable |
| 5 | 2003-2009 | Sourceforge | 1.2-1.5 | HTTP/1.1 RFC2616 | 2.4 | 2.0 | Deprecated |
| 4 | 2001-2006 | Sourceforge | 1.2，J2ME | HTTP/1.1 RFC2616 | 2.3 | 1.2 | Ancient |
| 3 | 1999-2002 | Sourceforge | 1.2 | HTTP/1.1 RFC2068 | 2.2 | 1.1 | Fossilized |
| 2 | 1998-2000 | Mortbay | 1.1 | HTTP/1.0 RFC1945 | 2.1 | 1.0 | Legendary |
| 1 | 1995-1998 | Mortbay | 1.0 | HTTP/1.0 RFC1945 | – | – | Mythical |
2：jdk编译器版本对应的数字版本号
| 1.8 | 52 | 00 00 00 34 |
| 1.7 | 51 | 00 00 00 33 |
| 1.6 | 50 | 00 00 00 32 |
| 1.5 | 49 | 00 00 00 31 |
| 1.4 | 48 | 00 00 00 30 |
| 1.3 | 47 | 00 00 00 2F |
| 1.2 | 46 | 00 00 00 2E |
| 1.1 | 45 | 00 00 00 2D |
这里的版本号需要注意，看看上面的错误提示：Unsupported major.minor version 51.0
51对应的是jdk7（1.7）
=
=
=
finished
+
+
+