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servletpackage 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; }}如有任何問題，可以私信我。
新聞熱點
疑難解答
