根据书上的需求写了一些简单的servlet代码，启动时报错：
严重: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/testagain]]
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:192)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:916)
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:868)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1408)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1398)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/testagain]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
... 6 more
Caused by: java.lang.IllegalArgumentException: Invalid <url-pattern> listbookservlet in servlet mapping
at org.apache.catalina.core.StandardContext.addServletMapping(StandardContext.java:3150)
at org.apache.catalina.core.StandardContext.addServletMapping(StandardContext.java:3125)
at org.apache.catalina.startup.ContextConfig.configureContext(ContextConfig.java:1372)
at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1176)
at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:771)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:305)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5120)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 6 more
发现其中Caused by: java.lang.IllegalArgumentException: Invalid <url-pattern> listbookservlet in servlet mapping
说明servlet映射的url-pattern有问题。
我是用注解的方式写的servlet映射,应该将@WebServlet("cartservlet")写成@WebServlet("/cartservlet")，
这样问题就解决了。