参考书籍：《J2EE开源编程精要15讲》
MVC(Model View Controller)，Model(模型)表示业务逻辑层，View(视图)代表表述层，Controller(控制)表示控制层。
在Java Web应用程序中，
View部分一般用JSP和HTML构建。客户在View部分提交请求，在业务逻辑层处理后，把结果返回给View部分显示
Controller部分一般用Servlet组成，把用户的请求发给适当的业务逻辑组件处理；处理后又返回Controller，把结果转发给适当的View组件
Model部分包括业务逻辑层和数据库访问层，一般由JavaBean或EJB(Enterprise JavaBean,企业级JavaBean)构建。数据访问层也叫数据持久层，与数据库打交道，常用JDBC API或Hibernate构建。
示例：
View部分：
index.jsp
1 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> 2 <% 3 String path = request.getContextPath(); 4 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 5 %> 6 7 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 8 <html> 9 <head> 10 <base href="<%=basePath%>"> 11 12 <title>登陆界面</title> 13 <meta http-equiv="pragma" content="no-cache"> 14 <meta http-equiv="cache-control" content="no-cache"> 15 <meta http-equiv="expires" content="0"> 16 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> 17 <meta http-equiv="description" content="This is my page"> 18 <!-- 19 <link rel="stylesheet" type="text/css" href="styles.css"> 20 --> 21 </head> 22 23 <body> 24 <form method="post" action="LoginServlet"> 25 用户名:<input type="text" name="username" size="15"><br><br> 26 密  码:<input type="password" name="password" size="15"><br><br> 27 <input type="submit" name="submit" value="登陆"><br> 28 </form> 29 </body> 30 </html>
main.jsp
1 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
2 <%
3 String path = request.getContextPath();
4 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
5 %>
6
7 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
8 <html>
9 <head>
10 <base href="<%=basePath%>">
11
12 <title>主页面</title>
13
14 <meta http-equiv="pragma" content="no-cache">
15 <meta http-equiv="cache-control" content="no-cache">
16 <meta http-equiv="expires" content="0">
17 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
18 <meta http-equiv="description" content="This is my page">
19 <!--
20 <link rel="stylesheet" type="text/css" href="styles.css">
21 -->
22
23 </head>
24
25 <body>
26 <h1>
27 <%=session.getAttribute("username") %>,你成功登陆，现已进入主界面!
28 </h1>
29 </body>
30 </html>
register.jsp
1 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
2 <%
3 String path = request.getContextPath();
4 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
5 %>
6
7 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
8 <html>
9 <head>
10 <base href="<%=basePath%>">
11
12 <title>注册页面</title>
13
14 <meta http-equiv="pragma" content="no-cache">
15 <meta http-equiv="cache-control" content="no-cache">
16 <meta http-equiv="expires" content="0">
17 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
18 <meta http-equiv="description" content="This is my page">
19 <!--
20 <link rel="stylesheet" type="text/css" href="styles.css">
21 -->
22
23 </head>
24
25 <body>
26 <h1>
27 <%=session.getAttribute("username") %>,你未能成功登陆。
28 <br>现已进入注册页面，请注册你的信息!
29 </h1>
30 </body>
31 </html>
Controller部分：
LoginServlet.java
1 /**
2 * 控制组件，在web.xml中将<servlet-mapping>标签内的<url-pattern>设置为"/LoginServlet"，
3 * 所以能接受来自index.jsp中action="LoginServlet"的表单的HTTP POST请求
4 */
5 package login;
6
7 import java.io.IOException;
8 import java.io.PrintWriter;
9
10 import javax.servlet.ServletException;
11 import javax.servlet.http.HttpServlet;
12 import javax.servlet.http.HttpServletRequest;
13 import javax.servlet.http.HttpServletResponse;
14 import javax.servlet.http.HttpSession;
15
16 public class LoginServlet extends HttpServlet {
17
18 /**
19 * Constructor of the object.
20 */
21 public LoginServlet() {
22 super();
23 }
24
25 /**
26 * Destruction of the servlet. <br>
27 */
28 public void destroy() {
29 super.destroy(); // Just puts "destroy" string in log
30 // Put your code here
31 }
32
33 /**
34 * The doGet method of the servlet. <br>
35 *
36 * This method is called when a form has its tag value method equals to get.
37 *
38 * @param request the request send by the client to the server
39 * @param response the response send by the server to the client
40 * @throws ServletException if an error occurred
41 * @throws IOException if an error occurred
42 */
43 public void doGet(HttpServletRequest request, HttpServletResponse response)
44 throws ServletException, IOException {
45 doPost(request,response);
46
47 }
48
49 /**
50 * The doPost method of the servlet. <br>
51 *
52 * This method is called when a form has its tag value method equals to post.
53 *
54 * @param request the request send by the client to the server
55 * @param response the response send by the server to the client
56 * @throws ServletException if an error occurred
57 * @throws IOException if an error occurred
58 */
59 public void doPost(HttpServletRequest request, HttpServletResponse response)
60 throws ServletException, IOException {
61
62 //获取请求中的用户名和密码
63 String username=request.getParameter("username");
64 String password=request.getParameter("password");
65
66 //生成一个Session对象,在main.jsp和register.jsp中可以根据Session对象获取用户名
67 HttpSession session=request.getSession(true);
68 session.removeAttribute("username");
69 session.setAttribute("username", username);
70
71 //调用业务逻辑组件，检查该用户是否已注册
72 LoginHandler login=new LoginHandler();
73 boolean mark=login.checkLogin(username,password);
74
75 //根据查询结果跳转
76 if(mark)
77 response.sendRedirect("main.jsp");
78 else
79 response.sendRedirect("register.jsp");
80 }
81
82 /**
83 * Initialization of the servlet. <br>
84 *
85 * @throws ServletException if an error occurs
86 */
87 public void init() throws ServletException {
88 // Put your code here
89 }
90
91 }
Model部分
业务逻辑组件，LoginHandler.java
1 /**
2 * 业务逻辑组件，从数据访问组件DBPool中获得数据库链接，检查用户记录是否存在
3 */
4 package login;
5
6 import java.sql.*;
7
8 public class LoginHandler {
9 public LoginHandler(){}
10
11 Connection conn;
12 PreparedStatement ps;
13 ResultSet rs;
14
15 public boolean checkLogin(String username,String password){
16 DBPool con=new DBPool();
17 try{
18 conn=con.getConnection();
19 String sql="select * from UserInfo where username=? and password=?";
20 ps=conn.prepareStatement(sql);
21 ps.setString(1, username);
22 ps.setString(2, password);
23 rs=ps.executeQuery();
24 if(rs.next()){
25 conn.close();
26 return true;
27 }
28 conn.close();
29 }catch(SQLException e){
30 e.printStackTrace();
31 }
32 return false;
33 }
34 }
数据库访问组件，DBPool.java (MySQL数据库)
1 /**
2 * 数据访问组件，数据库类型为MySQL,
3 * 登陆数据库用户名:"root",
4 * 密码:"root",
5 * 数据库:"user",
6 * 表:"UserInfo"
7 */
8 package login;
9
10 import java.sql.*;
11
12 public class DBPool {
13 public Connection getConnection() throws SQLException{
14 Connection con=null;
15
16 try{
17 Class.forName("com.mysql.jdbc.Driver");
18 con=DriverManager.getConnection("jdbc:mysql://localhost:3306/user?useUnicode=true&characterEncoding=UTF-8", "root", "root");
19 }catch(ClassNotFoundException e){
20 e.printStackTrace();
21 }
22 return con;
23 }
24 }
配置文件web.xml
1 <?xml version="1.0" encoding="UTF-8"?> 2 <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"> 3 <display-name>Login_Proj</display-name> 4 <servlet> 5 <description>This is the description of my J2EE component</description> 6 <display-name>This is the display name of my J2EE component</display-name> 7 <servlet-name>LoginServlet</servlet-name> 8 <servlet-class>login.LoginServlet</servlet-class> 9 </servlet> 10 11 <servlet-mapping> 12 <servlet-name>LoginServlet</servlet-name> 13 <url-pattern>/LoginServlet</url-pattern> 14 </servlet-mapping> 15 <welcome-file-list> 16 <welcome-file>index.html</welcome-file> 17 <welcome-file>index.htm</welcome-file> 18 <welcome-file>index.jsp</welcome-file> 19 <welcome-file>default.html</welcome-file> 20 <welcome-file>default.htm</welcome-file> 21 <welcome-file>default.jsp</welcome-file> 22 </welcome-file-list> 23 </web-app>
工程下载地址：http://kuai.xunlei.com/d/Dgv0CdygNGn6VAQA5f7
PS：使用环境Win7 64bit+MyEclipse Professional 2014+phpMyAdmin-2.10.3
时间： 2025-01-31 08:28:57