背景介紹：公司使用的網(wǎng)絡(luò)容器是tomcat，引入了log4j，研發(fā)的代碼中記錄了詳細(xì)的日志。所有的網(wǎng)頁行為包括后套的job定時任務(wù)等，都會把日志按定義的級別寫入tomcat/log/catalina.out文件中。那么監(jiān)控該文件，就能捕獲可視頁面無法感知到的錯誤。
Linux下使用命令：

tail -f catalina.out |grep -C 36 ERROR

該命令實時讀取日志文件，把出現(xiàn)“ERROR”行的日志前后各36日志打印出來。

也可以把日志記錄到文本中：

tail -f catalina.out |grep -C 36 ERROR >>error.log

下面是改命令捕獲的一個錯誤日志，在頁面上測試時候，沒有彈出任何錯誤提示：

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)at com.mk.security.SSOFilter.doFilter(SSOFilter.java:221)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:522)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:1110)at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:785)at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1425)at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)at java.lang.Thread.run(Thread.java:745)2017-02-07 16:45:14.183 [catalina-exec-80] INFO com.mk.shop.service.ShopService - selectTradeStatisticsMapcom.mk.vo.StatisticsItemVo@3427a14c[date=02-06,ymddate=<null>,num=0,rate=0,ratestr=<null>,uv=0] 2017-02-07 16:45:14.189 [catalina-exec-80] INFO com.mk.shop.service.ShopService - selectTradeStatisticsMapcom.mk.vo.StatisticsItemVo@363f3a3a[date=02-05,ymddate=<null>,num=0,rate=0,ratestr=<null>,uv=0] 2017-02-07 16:45:14.196 [catalina-exec-80] INFO com.mk.shop.service.ShopService - selectTradeStatisticsMapcom.mk.vo.StatisticsItemVo@719b7a9e[date=02-04,ymddate=<null>,num=0,rate=0,ratestr=<null>,uv=0] 2017-02-07 16:45:14.201 [catalina-exec-80] INFO com.mk.shop.service.ShopService - selectTradeStatisticsMapcom.mk.vo.StatisticsItemVo@c80b0d6[date=02-03,ymddate=<null>,num=0,rate=0,ratestr=<null>,uv=0] 2017-02-07 16:45:14.207 [catalina-exec-80] INFO com.mk.shop.service.ShopService - selectTradeStatisticsMapcom.mk.vo.StatisticsItemVo@706dab29[date=02-02,ymddate=<null>,num=0,rate=0,ratestr=<null>,uv=0] 2017-02-07 16:45:14.212 [catalina-exec-80] INFO com.mk.shop.service.ShopService - selectTradeStatisticsMapcom.mk.vo.StatisticsItemVo@6161143e[date=02-01,ymddate=<null>,num=0,rate=0,ratestr=<null>,uv=0] 2017-02-07 16:45:14.219 [catalina-exec-80] ERROR c.m.b.controller.ExceptionResolver - java.lang.NullPointerExceptionat com.mk.shop.service.ShopService.lambda$selectTradeStatisticsMap$4(ShopService.java:241)at java.util.TimSort.countRunAndMakeAscending(TimSort.java:355)at java.util.TimSort.sort(TimSort.java:220)at java.util.Arrays.sort(Arrays.java:1512)at java.util.ArrayList.sort(ArrayList.java:1454)at java.util.Collections.sort(Collections.java:175)at com.mk.shop.service.ShopService.selectTradeStatisticsMap(ShopService.java:241)at com.mk.shop.service.ShopService$$FastClassBySpringCGLIB$$99569971.invoke(<generated>)at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:711)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85)at com.mk.web.aspect.CacheAspect.doArround(CacheAspect.java:61)at sun.reflect.GeneratedMethodAccessor442.invoke(Unknown Source)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:497)at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621)at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610)at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:68)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:98)at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:262)at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:644)at com.mk.shop.service.ShopService$$EnhancerBySpringCGLIB$$6790a1c6.selectTradeStatisticsMap(<generated>)at com.mk.shop.controller.ShopController.selectTradeStatisticsMap(ShopController.java:161)at com.mk.shop.controller.ShopController$$FastClassBySpringCGLIB$$8bbcf00f.invoke(<generated>)at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:711)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)at org.springframework.aop.framework.adapter.MethodBeforeAdviceInterceptor.invoke(MethodBeforeAdviceInterceptor.java:52)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)

找到日志，提供給開發(fā)同學(xué)，那么他自然就知道錯誤是怎么來的。
這個，是研發(fā)開發(fā)中，調(diào)試代碼跟蹤日志，自然而然發(fā)展出來追蹤錯誤的一種辦法。對于不懂代碼或者對代碼一知半解的測試來說，是發(fā)現(xiàn)錯誤一個不錯的選擇。

轉(zhuǎn)載于:https://www.cnblogs.com/windanchaos/p/6398791.html

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