// MVC：强制性的使应用的输入、处理和输出分开
// M：模型，包括JavaBean，业务逻辑处理和数据访问应该放在Model层
// V：视图，用户看到并与之交互的界面，负责展示数据，由html、jsp等来做

// C：控制，负责转发，将用户请求转发给模型层，经过处理后把结果返回到界面层，由servlet来做

一、视图层

1. 登陆界面login.jsp

<body bgcolor="pink"> 
 <center>
 用户登陆 <br> <hr>
 <form action="LoginClServlet"> <!-- 提交给控制层，在web.xml里配置的url -->
 账 号：<input type="text" name = "username"><br>
 密 码：<input type="text" name = "passwd"><br>
 <input type="submit" value="登陆">
 <input type = "reset" value="重置">
 </form>
 </center>
 </body>

2. 欢迎界面wel.jsp

<body>
登陆成功！<%=request.getParameter("username")%><br>
<a href="login.jsp">退出</a><hr>
</body>

二、控制层

1. 登陆转发Servlet：LoginClServlet.java

package com.jiang.controller;

 import java.io.IOException;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import com.jiang.model.UserBeanCl;

 public class LoginClServlet extends HttpServlet {

 private static final long serialVersionUID = -2923205347859728847L;
 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 //得到用户名和密码
 String u = request.getParameter("username");
 String p = request.getParameter("passwd");
 //使用模型（userBeanCl），完成对用户的验证
 UserBeanCl ubc = new UserBeanCl();
 if(ubc.checkUser(u, p)){
 request.getRequestDispatcher("wel.jsp").forward(request, response); 
 }else{
 request.getRequestDispatcher("login.jsp").forward(request, response);
 }
 }
 public void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 this.doGet(request, response);
 }


}
2. LoginClServlet.java配置

<servlet>
 <description>This is the description of my J2EE component</description>
 <display-name>This is the display name of my J2EE component</display-name>
 <servlet-name>LoginClServlet</servlet-name>
 <servlet-class>com.jiang.controller.LoginClServlet</servlet-class>
 </servlet>

 <servlet-mapping>
 <servlet-name>LoginClServlet</servlet-name>
 <url-pattern>/LoginClServlet</url-pattern>
 </servlet-mapping>

三、模型层

1. 用户Bean： UserBean.java

package com.jiang.model;

 public class UserBean {
 private String username;
 private String password;
 public String getUsername() {
 return username;
 }
 public void setUsername(String username) {
 this.username = username;
 }
 public String getPassword() {
 return password;
 }
 public void setPassword(String password) {
 this.password = password;
 }

 }

2. 用户登陆业务处理 UserBeanCl.java

package com.jiang.model;

 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;

 public class UserBeanCl {

 private Connection ct = null;
 private PreparedStatement ps = null;
 private ResultSet rs = null;

 // 验证用户
 public boolean checkUser(String u, String p) {
 boolean b = false;
 try {
 ConnDB cd = new ConnDB();
 ct = cd.getConn();
 ps = ct.prepareStatement("select password from t_user where username ='"
 + u + "'");
 rs = ps.executeQuery();
 if (rs.next()) {
 String dbPasswd = rs.getString("password");
 if (dbPasswd.equals(p)) {
 b = true;
 }
 }
 } catch (Exception ex) {
 ex.printStackTrace();
 } finally {
 this.close();
 }
 return b;
 }

 // 关闭资源
 public void close() {
 try {
 if (rs != null) {
 rs.close();
 rs = null;
 }
 }catch(Exception e){
 e.printStackTrace();
 }
 try{
 if (ps != null) {
 ps.close();
 rs = null;
 }
 }catch(Exception e){
 e.printStackTrace();
 }
 try{
 if (ct != null) {
 ct.close();
 ct = null;
 }
 } catch (Exception ex) {
 ex.printStackTrace();
 }
 }
 }


3. 数据库连接逻辑处理 ConnDB.java

package com.jiang.model;

 import java.sql.Connection;
 import java.sql.DriverManager;

 public class ConnDB {
 private Connection ct = null;

 public Connection getConn() {
 try {
 Class.forName("com.mysql.jdbc.Driver");
 ct = DriverManager.getConnection(
 "jdbc:mysql://localhost:3306/aaa", "root", null);

 } catch (Exception ex) {
 // TODO Auto-generated catch block
 ex.printStackTrace();
 }
 return ct;
 }
 }