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 { @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 { @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; } }
如有任何问题，可以私信我。
