报错：Servlet.service() for servlet [dispatcherServlet] in context with path [/XXX] threw exception...

先把原因放上来：博主是数据库数据丢失的问题，如果确定自己的数据库正确无误的朋友就可以退出寻找其它解决办法了。

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问答

m0_56426418

11774人浏览 · 2023-06-08 09:44:44

m0_56426418 · 2023-06-08 09:44:44 发布

前言：

先把原因放上来：博主是数据库数据丢失的问题，如果确定自己的数据库正确无误的朋友就可以退出寻找其它解决办法了。

报错重点信息：

Servlet.service() for servlet [dispatcherServlet] in context with path [/XXX] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause

起因：

学习spring项目到后期遇到了问题：项目启动后打开页面就会报错，困扰了整整两天。从早到晚排错，整个人精神状态很差。

没办法，因为项目后期整合了太多东西，一个人很难定位到错误发生的根本地方。最后只能还原项目的版本，最终将长篇的报错信息缩小到如下内容：

ERROR [http-nio-8080-exec-1] o.a.c.c.C.[.[.[.[dispatcherServlet] [DirectJDKLog.java:175] Servlet.service() for servlet [dispatcherServlet] in context with path [/XXX] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException: null
   at org.programmer.community.controller.HomeController.getIndexPage(HomeController.java:47)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:498)
   at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
   at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
   at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
   at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:892)
   at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797)
   at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
   at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1039)
   at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942)
   at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005)
   at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897)
   at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
   at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882)
   at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
   at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
   at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
   at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
   at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92)
   at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
   at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93)
   at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
   at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
   at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
   at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:200)
   at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
   at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
   at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
   at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
   at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
   at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
   at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
   at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
   at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:836)
   at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1747)
   at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
   at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
   at java.lang.Thread.run(Thread.java:748)

解决：

当一看到报错中包含空指针错误时，立马就明白是数据库的问题了。

为什么把原因归结与数据库而不是其它呢？这也算是一点小经验，与大家分享：那就是通过打印的方式不断缩小可能引起错误的范围。

博主这里页面对应的Controller类主要就是调用业务层的方法将从数据库查询到的字段放到集合中。后续通过打印的方式明确控制层代码执行的某一步没有获取到数据，输出结果为null，再结合空指针的报错信息，一切都明朗了起来。

后记：

让我们回到两天前看看到底发生什么了。原来是自己手贱删了几条数据。。。。。。

家人们，谁懂啊？整无语了。。。谁让自己又菜又手贱。。。

本篇内容到这里就结束了，学习永无止境，排错也永无止境。虽然花了两天时间，但问题存在的意义就是被解决。

如果对你有帮助，请帮我点个👍支持一下，十分感谢！

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