MVC模式構建JavaWeb程序【有圖解有源碼，易理解易掌握】

2019-11-14 09:03:20

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來源：轉載

供稿：網友

一、MVC設計模式基礎

1.第一層V，即View，是視圖層，通常情況下是jsp頁面或HTML頁面，JSP頁面中主要由JSTL標簽以及EL表達式來顯示Servlet傳來的數據，并且通過用戶操作來傳遞數據給控制層。

2.第二層C，即Controller，是控制層，基本上是Servlet程序，接收來自視圖層傳來的數據，發送給第三層業務邏輯層，讓其處理后，根據不同的數據，來控制視圖層的顯示，起到了數據與視圖之間的橋梁作用。

3.第三層M，即Model，是組件層，控制著業務邏輯，接收控制層傳來的數據，并與持久層（數據庫）交互，反饋給控制層，所有的業務邏輯代碼均在組件層內。

二、基于MVC設計模式開發javaWeb程序的圖解。

這是一個簡單的用Maven構建的JavaWeb程序，具有登錄注冊功能。下面是圖解。

三、源代碼

1.登錄頁面

<%@ 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>登錄</title></head><body>	<h1>登錄</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.注冊頁面
<%@ 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>注冊</title></head><body>	<h1>注冊</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.登陸后的主頁面
<%@ 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>	用戶名：${sessionScope.userInfo.username }</body></html>
4.控制登錄的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 {		@Override	PRotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{		doPost(request, response);	}	@Override	protected 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.控制注冊的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 {	@Override	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException{		doPost(request, response);	}	@Override	protected 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.登錄業務邏輯組件
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.注冊業務邏輯組件
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.數據庫操作組件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		{			//加載驅動			Class.forName("com.mysql.jdbc.Driver");			//此時MySQL的Driver已經加入到DriverManager中，然后連接數據庫			connection = DriverManager.getConnection(url, username, password);		}		catch(Exception e)		{			logger.fine("連接失敗");;			e.printStackTrace();		}		return connection;	}	//獲得Statement類的對象，可以用此對象的方法執行sql語句	public Statement getStatement()	{		this.connect();		logger.info("con" + connection.toString());		try		{				statement = connection.createStatement();		}catch (Exception e)		{			logger.info("獲取statement失敗");			e.printStackTrace();		}				return statement;	}	public PreparedStatement getPreparedStatement(String sql){		this.connect();		PreparedStatement pstmt = null; 		try {			pstmt = connection.prepareStatement(sql);		} catch (SQLException e) {			logger.info("獲取preparedstatement失敗");		}		return pstmt;	}	//查詢	public ResultSet query(String sql)	{		this.getStatement();		logger.info("sta" + statement.toString());		try		{			resultSet = statement.executeQuery(sql);		}		catch (Exception e) 		{			logger.info("獲取結果集失敗");			e.printStackTrace();		}		logger.info("res" + resultSet);		return resultSet;	}	//更新數據庫	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("更新失敗");			e.printStackTrace();		}		return i;	}}
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