java.lang.UnsupportedClassVersionError问题调试

java.lang.UnsupportedClassVersionError: com/sand/mcs/pub/core/Publish : Unsupported major.minor version 51.0 (unable to load class com.sand.mcs.pub.core.Publish)
        at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2908)
        at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1173)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1681)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
        at com.sand.smp.server.core.util.CT.<clinit>(CT.java:610)
        at com.sand.smp.server.core.svc.MutilChannelHelpSvc.calMonitor(MutilChannelHelpSvc.java:86)
        at com.sand.smp.server.core.svc.impl.MutilChannelSvcImpl.walletStatQuery(MutilChannelSvcImpl.java:2869)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
        at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96)
        at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)
        at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
        at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:91)
        at com.sand.smp.server.core.monitor.MonitorAspect.doAround(MonitorAspect.java:28)
        at sun.reflect.GeneratedMethodAccessor127.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)


看报错信息，是因为使用的jar包版本不对。这个51.0是什么呢？

　　JDK不同的版本，编译出的class文件是不同的。通过查看分析class文件前几个字节，可以找到对应的关系，详细的参考官方，细微的版本之间可能有差异：

J2SE 7 = 51 (0x33 hex),
J2SE 6.0 = 50 (0x32 hex),
J2SE 5.0 = 49 (0x31 hex),
JDK 1.4 = 48 (0x30 hex),
JDK 1.3 = 47 (0x2F hex),
JDK 1.2 = 46 (0x2E hex),
JDK 1.1 = 45 (0x2D hex).

查看jar包的配置文件：



解决方式：
修改项目编译jre版本为1.7.0_79，重新打war包发布，问题解决。