MVC模式构建JavaWeb程序【有图解有源码，易理解易掌握】

来源：互联网发布：淘宝开店心得和经验编辑：程序博客网时间：2024/06/10 09:42

一、MVC设计模式基础

1.第一层V，即View，是视图层，通常情况下是JSP页面或HTML页面，JSP页面中主要由JSTL标签以及EL表达式来显示Servlet传来的数据，并且通过用户操作来传递数据给控制层。

2.第二层C，即Controller，是控制层，基本上是Servlet程序，接收来自视图层传来的数据，发送给第三层业务逻辑层，让其处理后，根据不同的数据，来控制视图层的显示，起到了数据与视图之间的桥梁作用。

3.第三层M，即Model，是组件层，控制着业务逻辑，接收控制层传来的数据，并与持久层（数据库）交互，反馈给控制层，所有的业务逻辑代码均在组件层内。

二、基于MVC设计模式开发JavaWeb程序的图解。

这是一个简单的用Maven构建的JavaWeb程序，具有登录注册功能。下面是图解。

三、源代码

1.登录页面

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!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=UTF-8"><title>登录</title></head><body><h1>登录</h1><form action="LoginController" method="POST"><input type="text" name="username"/><input type="password" name="password"/><input type="submit" name="submit"/></form></body></html>

2.注册页面

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!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=UTF-8"><title>注册</title></head><body><h1>注册</h1><form action="RegisterController" method="POST"><input type="text" name="username"/><input type="password" name="password"/><input type="submit" name="submit"/></form></body></html>

3.登陆后的主页面

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!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=UTF-8"><title>主界面</title></head><body>用户名：${sessionScope.userInfo.username }</body></html>

4.控制登录的servlet

package servlet.controller;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.*;import dao.LoginHandler;import javabeans.UserInfo;public class LoginController extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{doPost(request, response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{response.setContentType("text/html");UserInfo userInfo = new UserInfo();userInfo.setUsername((String)request.getParameter("username"));userInfo.setPassword((String)request.getParameter("password"));LoginHandler handler = new LoginHandler();if(handler.check(userInfo)){HttpSession session = request.getSession(true);session.setAttribute("userInfo", userInfo);request.getRequestDispatcher("/WEB-INF/main.jsp").forward(request, response);}else{response.sendRedirect("login.jsp");}}}

5.控制注册的servlet

package servlet.controller;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.*;import dao.RegisterHandler;import javabeans.UserInfo;public class RegisterController extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException{doPost(request, response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException{response.setContentType("text/html");UserInfo userInfo = new UserInfo();userInfo.setUsername(request.getParameter("username"));userInfo.setPassword(request.getParameter("password"));RegisterHandler handler = new RegisterHandler();if(handler.register(userInfo)){response.sendRedirect(getServletConfig().getServletContext().getContextPath() + "/login.jsp");}else{response.sendRedirect(getServletConfig().getServletContext().getContextPath() + "/register.jsp");}}}

6.登录业务逻辑组件

package dao;import java.sql.*;import javabeans.UserInfo;import utils.DB;public class LoginHandler {private boolean flag = false;public boolean check(UserInfo userInfo){DB db = new DB();PreparedStatement pstmt = db.getPreparedStatement("SELECT * FROM user_table WHERE username=?");try {pstmt.setString(1, userInfo.getUsername());ResultSet rs = pstmt.executeQuery();while(rs.next()){System.out.println(rs.getString(2));if(userInfo.getPassword().equals(rs.getString(2))){flag = true;}}} catch (SQLException e) {e.printStackTrace();}return flag;}}

7.注册业务逻辑组件

package dao;import java.sql.*;import javabeans.UserInfo;import utils.DB;public class RegisterHandler {public boolean register(UserInfo userInfo){DB db = new DB();PreparedStatement pstmt = db.getPreparedStatement("SELECT * FROM user_table WHERE username=?");try {pstmt.setString(1, userInfo.getUsername());ResultSet rs = pstmt.executeQuery();if(rs.next()){return false;}pstmt = db.getPreparedStatement("INSERT INTO user_table VALUES(?,?)");pstmt.setString(1, userInfo.getUsername());pstmt.setString(2, userInfo.getPassword());pstmt.execute();return true;} catch (SQLException e) {e.printStackTrace();return false;}}}

8.数据库操作组件

package utils;import java.sql.*;import java.util.logging.Logger;public class DB{private Connection connection = null;private ResultSet resultSet = null;private Statement statement = null;private String dbName = "db";private String username = "root";private String password = "admin";private String url = "jdbc:mysql://localhost:3306/" + dbName;private Logger logger = Logger.getLogger(this.getClass().getName());public DB(){};public Connection connect(){try{//加载驱动Class.forName("com.mysql.jdbc.Driver");//此时MySQL的Driver已经加入到DriverManager中，然后连接数据库connection = DriverManager.getConnection(url, username, password);}catch(Exception e){logger.fine("连接失败");;e.printStackTrace();}return connection;}//获得Statement类的对象，可以用此对象的方法执行sql语句public Statement getStatement(){this.connect();logger.info("con" + connection.toString());try{statement = connection.createStatement();}catch (Exception e){logger.info("获取statement失败");e.printStackTrace();}return statement;}public PreparedStatement getPreparedStatement(String sql){this.connect();PreparedStatement pstmt = null; try {pstmt = connection.prepareStatement(sql);} catch (SQLException e) {logger.info("获取preparedstatement失败");}return pstmt;}//查询public ResultSet query(String sql){this.getStatement();logger.info("sta" + statement.toString());try{resultSet = statement.executeQuery(sql);}catch (Exception e) {logger.info("获取结果集失败");e.printStackTrace();}logger.info("res" + resultSet);return resultSet;}//更新数据库public int update(String sql){int i = -1;this.getStatement();try{i = statement.executeUpdate(sql);logger.info("插入后i=" + i);}catch(Exception e){logger.info("更新失败");e.printStackTrace();}return i;}}

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