严重: Servlet.service() for servlet [SpringMVC] in context with path [/MVCQ] threw exception [Request

十二月 28, 2018 8:05:57 下午 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet [SpringMVC] in context with path [/MVCQ] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException
	at com.qiu.interceptor.MyInterceptor.postHandle(MyInterceptor.java:40)
	at org.springframework.web.servlet.HandlerExecutionChain.applyPostHandle(HandlerExecutionChain.java:152)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:950)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)

十二月 28, 2018 8:06:03 下午 org.apache.catalina.core.StandardContext reload
信息: Reloading Context with name [/MVCQ] has started
十二月 28, 2018 8:06:03 下午 org.apache.catalina.core.ApplicationContext log
信息: Destroying Spring FrameworkServlet 'SpringMVC'
十二月 28, 2018 8:06:04 下午 org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
严重: The web application [/MVCQ] registered the JDBC driver [com.alibaba.druid.proxy.DruidDriver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
十二月 28, 2018 8:06:04 下午 org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
严重: The web application [/MVCQ] registered the JDBC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
十二月 28, 2018 8:06:04 下午 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
严重: The web application [/MVCQ] appears to have started a thread named [Abandoned connection cleanup thread] but has failed to stop it. This is very likely to create a memory leak.
十二月 28, 2018 8:06:04 下午 org.apache.catalina.loader.WebappClassLoader validateJarFile
信息: validateJarFile(F:\ALL_Course\10Activiti\Ecli\.metadata\.plugins\org.eclipse.wst.server.core\tmp4\wtpwebapps\MVCQ\WEB-INF\lib\javax.servlet-api-3.1.0.jar) - jar not loaded. See Servlet Spec 3.0, section 10.7.2. Offending class: javax/servlet/Servlet.class
十二月 28, 2018 8:06:06 下午 org.apache.catalina.core.ApplicationContext log
信息: No Spring WebApplicationInitializer types detected on classpath
log4j:WARN No appenders could be found for logger (org.springframework.web.context.support.StandardServletEnvironment).
log4j:WARN Please initialize the log4j system properly.
十二月 28, 2018 8:06:06 下午 org.apache.catalina.core.ApplicationContext log
信息: Initializing Spring FrameworkServlet 'SpringMVC'
SLF4J: This version of SLF4J requires log4j version 1.2.12 or later. See also http://www.slf4j.org/codes.html#log4j_version
十二月 28, 2018 8:06:09 下午 org.apache.catalina.core.StandardContext reload
信息: Reloading Context with name [/MVCQ] is completed

（1）、原因：导包导错了！

（2）、说可以把Dao层的getCurrentSession()方法换为openSession()方法

【JDK1.7+Tomcat7.0】

我运行简单的控制器，很正常，接着我改了@RequestMapping的值，可能没及时反应或者及时编译，我访问对应URL，就报了这样的错误，我搜了百度，感觉有点道理，但是我还是“先重启”，结果好了~~~所以有异常出现之后，先确定“配置文件是否异常”再确定“相应代码是否有异常”，确定无误之后，请重启Tomcat或者重启编译器（Eclipse）