SpringMVC-FAQ（1）：HTTP Status 500 - Servlet.init() for servlet DispatcherServlet threw exception

（1）：看Log

type Exception report

message Servlet.init() for servlet DispatcherServlet threw exception

description The server encountered an internal error that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Servlet.init() for servlet DispatcherServlet threw exception
	org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
	org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
	org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
	org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:502)
	org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1132)
	org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:684)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1539)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1495)
	java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	java.lang.Thread.run(Unknown Source)

root cause

java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "accessDeclaredMembers")
	java.security.AccessControlContext.checkPermission(Unknown Source)
	java.security.AccessController.checkPermission(Unknown Source)
	java.lang.SecurityManager.checkPermission(Unknown Source)
	java.lang.Class.checkMemberAccess(Unknown Source)
	java.lang.Class.getDeclaredMethods(Unknown Source)
	org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:613)
	org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:524)
	org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:537)
	org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:510)
	org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:247)
	org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineConstructorsFromBeanPostProcessors(AbstractAutowireCapableBeanFactory.java:1118)
	org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1091)
	org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513)
	org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483)
	org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
	org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
	org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
	org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
	org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761)
	org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867)
	org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543)
	org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:668)
	org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:634)
	org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:682)
	org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:553)
	org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:494)
	org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:171)
	javax.servlet.GenericServlet.init(GenericServlet.java:158)
	sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	java.lang.reflect.Method.invoke(Unknown Source)
	org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:293)
	org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:290)
	java.security.AccessController.doPrivileged(Native Method)
	javax.security.auth.Subject.doAsPrivileged(Unknown Source)
	org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:325)
	org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:176)
	org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:124)
	org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
	org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
	org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
	org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:502)
	org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1132)
	org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:684)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1539)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1495)
	java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	java.lang.Thread.run(Unknown Source)

note The full stack trace of the root cause is available in the Apache Tomcat/8.0.47 logs.

（2）分析：

      前端控制器（dispatcherServlet）Servlet初始化异常。

（3）原理：

     DispatcherServlet 是一个实实在在的 Servlet，所以 Spring MVC 引入后不会改变 Servlet 容器的行为，仍然是解析 web.xml 部署文件，只需要在里面配置这个 Servlet 即可。  

     DispatcherServlet 中具体实现请求的处理分发，先是把一些资源放到请求属性中，然后调用 doDispatch 实现请求分发到控制器的 handler