名为[Myclass]和[mypackage.Myclass]的servlet都映射到url模式[/Myclass]，这

Question

启动服务器时发生以下错误

localhost上的服务器Tomcat v7.0服务器无法启动。

当我查看控制台中的错误时，我认为这就是问题"名为[Myclass]和[mypackage.Myclass]的servlet都映射到url模式[/Myclass]，这是不允许的"。

这里的问题是什么？如何解决？

Web.xml代码

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xmlns="http://java.sun.com/xml/ns/javaee" 
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee      
         http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID"   
         version="3.0">
   <display-name>myproject</display-name>
   <welcome-file-list>
      <welcome-file>index.html</welcome-file>
      <welcome-file>index.htm</welcome-file>
      <welcome-file>index.jsp</welcome-file>
      <welcome-file>default.html</welcome-file>
      <welcome-file>default.htm</welcome-file>
      <welcome-file>default.jsp</welcome-file>
   </welcome-file-list>
   <servlet>
      <servlet-name>Myclass</servlet-name>
      <servlet-class>mypropackage.Myclass</servlet-class>
   </servlet>
   <servlet-mapping>
      <servlet-name>Myclass</servlet-name>
      <url-pattern>/myclass</url-pattern>
   </servlet-mapping>
</web-app>

Servlet类代码：

package mypropackage;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 /**
 * Servlet implementation class Myclass
 */
 @WebServlet("/myclass")
 public class Myclass extends HttpServlet {
    private static final long serialVersionUID = 1L;
    /**
     * @see HttpServlet#HttpServlet()
     */
    public Myclass() {
        super();
        // TODO Auto-generated constructor stub
    }
    /**
     * @see Servlet#init(ServletConfig)
     */
    public void init(ServletConfig config) throws ServletException {
        // TODO Auto-generated method stub
    }
    /**
     * @see HttpServlet#service(HttpServletRequest request,    
  HttpServletResponse response)
     */
    protected void service(HttpServletRequest request,    
    HttpServletResponse response) throws ServletException, IOException {
        System.out.println("service method");
        String uname = "user";
        String pass = "abcd";
        String un = request.getParameter("username");
        String pw = request.getParameter("password");
        String msg = " ";
        if(un.equals(uname) && pw.equals(pass))
        {
            msg = "hello" + un + "login successful";
        }
        else
        {
            msg = "hello" + pw + "login failed";
        }
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println(msg);
    }
  }

这是控制台中的日志：

Caused by: java.lang.IllegalArgumentException: The servlets named [Myclass] and [mypropackage.Myclass] are both mapped to the url-pattern [/myclass] which is not permitted
    at org.apache.catalina.deploy.WebXml.addServletMapping(WebXml.java:293)
    at org.apache.catalina.startup.ContextConfig.processAnnotationWebServlet(ContextConfig.java:2428)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsStream(ContextConfig.java:2103)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:2064)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:2057)
    at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1304)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:889)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:386)
    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:5412)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 6 more

Answer 1

您确实定义了两次servlet：

1. 在类mypropackage.MyClass 中使用@WebServlet("/myclass")注释

2. 使用定义servlet Myclass的web.xml。

servlet的两个实例都映射到同一个URL，这就是容器告诉您的。您只需要使用其中一种方法来定义servlet：使用注释或使用web.xml。我更喜欢使用web.xml，但这可能是因为在注释发明之前几年，我曾在那里定义servlet。因此，欢迎您自己做出选择。

使用web.xml的IMHO更加灵活。您不必在开发时决定映射servlet的URL，并且可以多次部署同一servlet并将其映射到多个URL。