JAVA开发debug之道

r囧r小猫 2021-10-18 15:46 271阅读 0赞

开发调试时，难免会出各种各样幺*蛾子，别怕，不出bug的程序员不是好程序员！关键我们怎么来解决些问题！*

*  一、认真查看报错信息*

*      如下图，虽然看起来一长串的报错信息很恐怖，实际关键信息都告诉你了，问题就出在第一行的“ManpowerCostController.java:59”！*

java.lang.NullPointerException: null
    	at com.***.controller.ManpowerCostController.AccrualWagesByMonth(ManpowerCostController.java:59)
    	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:205)
    	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
    	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
    	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
    	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
    	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
    	at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
    	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    	at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    	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:52)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    	at org.springframework.boot.web.filter.ApplicationContextHeaderFilter.doFilterInternal(ApplicationContextHeaderFilter.java:55)
    	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 com.**.filter.LogFilter.doFilter(LogFilter.java:34)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    	at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:110)
    	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.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.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105)
    	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:81)
    	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 com.**.instrument.filter.MoeyeTraceFilter.doFilter(MoeyeTraceFilter.java:62)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    	at org.springframework.cloud.sleuth.instrument.web.TraceFilter.doFilter(TraceFilter.java:169)
    	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:197)
    	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.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:106)
    	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:198)
    	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
    	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
    	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799)
    	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
    	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455)
    	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)

二、积极从蛛丝马迹中查找线索，打开突破口

[INFO] ------------------------------------------------------------------------
    [INFO] BUILD FAILURE
    [INFO] ------------------------------------------------------------------------
    [INFO] Total time: 57.049 s
    [INFO] Finished at: 2019-08-12T18:42:27+08:00
    [INFO] Final Memory: 155M/1381M
    [INFO] ------------------------------------------------------------------------
    [ERROR] Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:1.5.6.RELEASE:run (default-cli) on project **: An exception occurred while running. null: InvocationTargetException: Error creating bean with name 'manpowerCostController': Unsatisfied dependency expressed through field 'hrisClient'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.**.client.hris.HrisClient' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} -> [Help 1]
    [ERROR] 
    [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
    [ERROR] Re-run Maven using the -X switch to enable full debug logging.
    [ERROR]

上面的报错信息中，“No qualifying bean of type”是关键线索，查下就知道是bean没有注入造成的。

三、好好利用搜索及其他工具。

度娘虽然再怎么不被人瞧不起，但搜索问题还有很有效果的。否则，就搭梯子翻墙上google吧。