解決Invalid servletDemo in servlet mapping 問題

 　在學習Servlet時，啟動tomcat服務時報錯日志如下

java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/servlet]]
    at java.util.concurrent.FutureTask.report(FutureTask.java:122)
    at java.util.concurrent.FutureTask.get(FutureTask.java:188)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1119)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:819)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1571)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1561)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/servlet]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:153)
    ... 6 more
Caused by: java.lang.IllegalArgumentException: Invalid <url-pattern> servletDemo in servlet mapping
    at org.apache.catalina.core.StandardContext.addServletMapping(StandardContext.java:3410)
    at org.apache.catalina.core.StandardContext.addServletMapping(StandardContext.java:3385)
    at org.apache.catalina.deploy.WebXml.configureContext(WebXml.java:1438)
    at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1355)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:887)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:387)
    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:5503)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    ... 6 more

　　　　檢查web.xml配置文件並未發現有哪里配錯。

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee                       
                            http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">

  <servlet>
          <servlet-name>servletDemo</servlet-name>
          <servlet-class>com.xzp.servlet.ServletDemo</servlet-class>
  </servlet>
  <servlet-mapping>
          <servlet-name>servletDemo</servlet-name>
          <url-pattern>/*</url-pattern>
  </servlet-mapping>
  
</web-app>

　　　　查看Servlet應用程序demo，發現注解@WebServlet的urlPatterns 配置有誤。

 1 @WebServlet(urlPatterns = "servletDemo")
public class ServletDemo extends HttpServlet {
    //初始化方法
    @Override
    public void init() throws ServletException {
        System.out.println("初始化");
        super.init();
    }
    //執行get請求的業務處理
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("執行get請求");
        super.doGet(req, resp);
    }
    //執行post請求的業務處理
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("執行post請求");
        super.doPost(req, resp);
    }    
    //銷毀
    @Override
    public void destroy() {
        System.out.println("銷毀");
        super.destroy();
    }
}

　　  解決辦法：

　　　　@WebServlet(urlPatterns = "servletDemo")   改為   @WebServlet(urlPatterns = "/servletDemo")。