用struts2和mysql寫的網(wǎng)站，大致就是從數(shù)據(jù)庫讀取信息列表，再剛啟動(dòng)tomcat的時(shí)候都沒有問題，可是時(shí)間一長（可能么大概要好幾個(gè)小時(shí)，沒法準(zhǔn)確定位時(shí)間），就出現(xiàn)空指針異常的錯(cuò)誤，刷新一下又能正常顯示（多次刷新還是會(huì)出現(xiàn)報(bào)錯(cuò)），重啟tomcat之后在一段時(shí)間內(nèi)不會(huì)出現(xiàn)這種情況，貼下部分報(bào)錯(cuò)信息Stacktracesjava.lang.NullPointerException????com.kongtrolink.service.impl.NewsDaoImpl.queryAllNews(NewsDaoImpl.java:36) ????com.kongtrolink.action.NewsAction.query(NewsAction.java:28) ????sun.reflect.GeneratedMethodAccessor122.invoke(Unknown?Source) ????sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ????java.lang.reflect.Method.invoke(Method.java:497) ????com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:441) ????com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:280) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:243) ????com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:165) ????com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:252) ????org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68) ????com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195) ????com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195) ????com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:179) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:235) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:130) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138) ????com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:165) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:179) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176) ????com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237) ????org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52) ????org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:488) ????org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77) ????org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91) ????com.kongtrolink.filter.UeditorFilter.doFilter(UeditorFilter.java:23) ????org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) ????org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) ????org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:217) ????org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) ????org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) ????org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) ????org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) ????org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) ????org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) ????org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) ????org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:673) ????org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500) ????org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456) ????java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) ????java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) ????org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ????java.lang.Thread.run(Thread.java:745)