今天在開發的過程中遇到一個錯誤與大家分享一下 :我遇到的錯誤是 java.lang.NoClassDefFoundError 這個錯誤的意思是什么了？沒有找到定義的類的錯誤。與之相似的一個異常時java.lang.NotClassFound，這個異常表名沒有找到類。馬虎的開發人員可能會把 第一個錯誤當成第二個錯誤去處理，如果這樣你就上當了。
- 先說一下java.lang.NotClassFound 與 java.lang.NoClassDefFoundError的區別：java.lang.NoClassDefFoundError 是unchecked Exception（也就是常說的運行時異常），java.lang.NotClassFound 是checkedException 對於這兩種異常不熟悉的朋友請自行學習。
- java.lang.NotClassFound 造成的原因一般是缺少類文件，或者缺少jar造成的，解決方案是去查找異常指向的類，添加相應的jar或者類文件。
- java.lang.NoClassDefFoundError 產生的原因是 在類中有着靜態的方法或者靜態的方法塊，去掉之后異常解除。具體原因有待分析
Caused by: java.lang.NoClassDefFoundError: Could not initialize class com.thinkgem.jeesite.common.sys.utils.UserUtils
at com.thinkgem.jeesite.cms.service.CategoryServiceImpl.findByUser(CategoryServiceImpl.java:41)
at com.thinkgem.jeesite.cms.service.CategoryServiceImpl$$FastClassBySpringCGLIB$$7d62ae78.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:708)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:98)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:262)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:644)
at com.thinkgem.jeesite.cms.service.CategoryServiceImpl$$EnhancerBySpringCGLIB$$5b7c636a.findByUser(<generated>)
at com.alibaba.dubbo.common.bytecode.Wrapper2.invokeMethod(Wrapper2.java)
at com.alibaba.dubbo.rpc.proxy.javassist.JavassistProxyFactory$1.doInvoke(JavassistProxyFactory.java:46)
at com.alibaba.dubbo.rpc.proxy.AbstractProxyInvoker.invoke(AbstractProxyInvoker.java:72)
at com.alibaba.dubbo.rpc.protocol.InvokerWrapper.invoke(InvokerWrapper.java:53)
at com.alibaba.dubbo.rpc.filter.ExceptionFilter.invoke(ExceptionFilter.java:64)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.filter.TimeoutFilter.invoke(TimeoutFilter.java:42)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.monitor.support.MonitorFilter.invoke(MonitorFilter.java:75)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.protocol.dubbo.filter.TraceFilter.invoke(TraceFilter.java:78)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.filter.ContextFilter.invoke(ContextFilter.java:60)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.filter.GenericFilter.invoke(GenericFilter.java:112)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.filter.ClassLoaderFilter.invoke(ClassLoaderFilter.java:38)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.filter.EchoFilter.invoke(EchoFilter.java:38)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply(DubboProtocol.java:108)
at com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest(HeaderExchangeHandler.java:84)
at com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:170)
at com.alibaba.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:52)
at com.alibaba.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:82)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
... 1 more