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我的第一个 servlet 有问题。我创建了 index.jsp、类和 servlet。代码如下：

索引.jsp：

<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"     "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Blog</title>
</head>
<body>
<table>
      <thead>
           <tr>
                <td>Username:</td>
                <td>Title:</td>
                <td>Message:</td>
           </tr>
      </thead>
      <c:forEach items="${messages}" var="mess">
           <tr>
                <td>${mess.name}</td>
                <td>${mess.title}</td>
                <td>${mess.text}</td>
           </tr>
      </c:forEach>
 </table>

</body>
</html>

BlogServlet.java：

package servlets;


import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import blog.Message;



/**
 * Servlet implementation class for Servlet: BlogServlet
 *
*/
 public class BlogServlet extends javax.servlet.http.HttpServlet implements     javax.servlet.Servlet {
 static final long serialVersionUID = 1L;
 private EntityManagerFactory factory;
 private EntityManager em;
 /* (non-Java-doc)
 * @see javax.servlet.http.HttpServlet#HttpServlet()
 */
public BlogServlet() {
    super();
    factory = Persistence.createEntityManagerFactory("blog");
    em = factory.createEntityManager();
}       

/* (non-Java-doc)
 * @see javax.servlet.http.HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    List<Message> messages = 
           em.createQuery("select * from Messages m").getResultList();
   request.setAttribute("messages", messages);
   request.getRequestDispatcher("/index.jsp").forward(request, response);
}   

/* (non-Java-doc)
 * @see javax.servlet.http.HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    this.doGet(request, response);
}               
}

网页.xml：

<?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" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee   http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>BlogServlet</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>
  <description></description>
  <display-name>BlogServlet</display-name>
  <servlet-name>BlogServlet</servlet-name>
  <servlet-class>servlets.BlogServlet</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>BlogServlet</servlet-name>
  <url-pattern>/servlets/BlogServlet</url-pattern>
</servlet-mapping>

Tomcat 返回错误消息“请求的资源不可用”。我究竟做错了什么？

4

0 回答 0