一、方法调用错误

至少我同桌是这么做的,在IDEA的Servlet模板没配好之前,一般会在doPost或doGet请求中填写this.doGet/doPost(request,response),而有部分初学者会写成方法调用自己,注意:这个就会变成递归。这样编写过程中不会报错但是在页面请求之后500就来了,页面错误会有如下所示的错误码:

java.lang.StackOverflowError
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)
	web.servlet.FindUserByPageServlet.doGet(FindUserByPageServlet.java:55)

二、Servlet使用注解开发时没有书写正确value(默认)值

这个问题多半来自IDEA手动创建Servlet时注解中的name改默认的value时忘记加"/"引发的,这个问题在服务启动时会报生命周期异常(LifecycleException: Failed to start component ),会显示如下代码块:

06-Jan-2019 08:45:02.772 严重 [RMI TCP Connection(2)-127.0.0.1] org.apache.catalina.core.ContainerBase.addChildInternal ContainerBase.addChild: start: 
 org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
	at org.apache.catalina.util.LifecycleBase.handleSubClassException(LifecycleBase.java:441)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:198)
	at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:743)
	at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:719)
	at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:703)
	at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1737)
	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.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:287)
	at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
	at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
	at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:457)
	at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:406)
	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.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:287)
	at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
	at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
	at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1468)
	at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
	at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1309)
	at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1401)
	at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:829)
	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 sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:357)
	at sun.rmi.transport.Transport$1.run(Transport.java:200)
	at sun.rmi.transport.Transport$1.run(Transport.java:197)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
	at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:573)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:834)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:688)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:687)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.IllegalArgumentException: Invalid <url-pattern> [userListServlet] in servlet mapping
	at org.apache.catalina.core.StandardContext.addServletMappingDecoded(StandardContext.java:3136)
	at org.apache.catalina.Context.addServletMappingDecoded(Context.java:879)
	at org.apache.catalina.startup.ContextConfig.configureContext(ContextConfig.java:1376)
	at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1187)
	at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:765)
	at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:299)
	at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:123)
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5007)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
	... 42 more


06-Jan-2019 08:45:02.773 严重 [RMI TCP Connection(2)-127.0.0.1] org.apache.tomcat.util.modeler.BaseModelMBean.invoke Exception invoking method manageApp
 java.lang.IllegalStateException: ContainerBase.addChild: start: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
	at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:747)
	at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:719)
	at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:703)
	at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1737)
	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.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:287)
	at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
	at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
	at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:457)
	at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:406)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[2019-01-06 08:45:02,778] Artifact day19-code:war exploded: Error during artifact deployment. See server log for details.
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:287)
	at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
	at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
	at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1468)
	at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
	at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1309)
	at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1401)
	at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:829)
	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 sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:357)
	at sun.rmi.transport.Transport$1.run(Transport.java:200)
	at sun.rmi.transport.Transport$1.run(Transport.java:197)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
	at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:573)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:834)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:688)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:687)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

06-Jan-2019 08:45:02.773 严重 [RMI TCP Connection(2)-127.0.0.1] org.apache.tomcat.util.modeler.BaseModelMBean.invoke Exception invoking method createStandardContext
 javax.management.RuntimeOperationsException: Exception invoking method manageApp
	at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:295)
	at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
	at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
	at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:457)
	at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:406)
	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.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:287)
	at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
	at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
	at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1468)
	at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
	at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1309)
	at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1401)
	at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:829)
	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 sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:357)
	at sun.rmi.transport.Transport$1.run(Transport.java:200)
	at sun.rmi.transport.Transport$1.run(Transport.java:197)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
	at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:573)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:834)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:688)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:687)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.IllegalStateException: ContainerBase.addChild: start: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
	at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:747)
	at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:719)
	at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:703)
	at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1737)
	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.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:287)
	... 33 more