Model1

显示层,控制层,数据层,统一交给jsp或者javabean处理.

处理流程

客户端发送request 到 jsp jsp 执行javabean javabean读取databases

返回 databases 返回给javabean 在返回给jsp 在response 给客户端

问题

代码杂乱
即 jsp + dao 方式

model - view - controller

客户端发送request 到servlet 然后servlet 执行javabean javabean用于读取databases 控制器,获取到javabean读取的数据以后,再次返回给jsp,jso生成html文件,response 给客户端
分为 显示层 控制层 模型层

EJB 属于SUN提供的分布式组件服务 分为会话bean 实体bean 消息驱动bean

实栗

一个登录程序
用户提交登录信息,发送给servlet servlet数据验证失败将会返回给登录页,同时servlet将会调用数据层操作dao,dao到数据库databases进行验证,结果返回给servlet 然后返回两个结果,登录成功,登录失败.

代码如下

创建数据库

目录结构如下

jdbc层

package com.ming.dbc;import java.sql.Connection;import java.sql.DriverManager;public class DatabaseConnection { ???private static final String DBDRIVER = "com.mysql.cj.jdbc.Driver"; ???private static final String DBURL = "jdbc:mysql://47.94.95.84:32786/test"; ???private static final String DBUSER = "test"; ???private static final String DBPASSWORD = "ABCcba20170607"; ???private Connection connection = null; ???// 连接数据库 ???public DatabaseConnection() throws Exception{ ???????try{ ???????????Class.forName(DBDRIVER); ???????????connection = DriverManager.getConnection(DBURL, DBUSER, DBPASSWORD); ???????}catch (Exception e){ ???????????throw e; ???????} ???} ???// 获得数据库连接 ???public Connection getConnection(){ ???????return this.connection; ???} ???// 数据库关闭 ???public void close() throws Exception{ ???????if(this.connection != null){ ???????????try{ ???????????????this.connection.close(); ???????????}catch (Exception e){ ???????????????throw ?e; ???????????} ???????} ???}}

dao层

定义接口

package com.ming.dao;import com.ming.vo.User;public interface IUserDAO { ???/** ????* 用户登录验证 ????* @param user 传入VO对象 ????* @return 验证操作结果 ????* @throws Exception 抛出错误 ????*/ ???public boolean findLogin(User user) throws Exception;}

实现类

package com.ming.dao;import com.ming.vo.User;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;public class UserDAOImpl implements IUserDAO { ???// 数据库连接对象 ???private Connection connection = null; ???// 操作对象 ???private PreparedStatement preparedStatement = null; ???// 数据库连接 ???public UserDAOImpl(Connection _connection){ ???????this.connection = _connection; ???} ???/** ????* 用户登录验证 ????* ????* @param user 传入VO对象 ????* @return 验证操作结果 ????* @throws Exception 抛出错误 ????*/ ???@Override ???public boolean findLogin(User user) throws Exception { ???????boolean flag = false; ???????try{ ???????????String sql = "SELECT name FROM user WHERE userid = ? AND password = ?"; ???????????// 获得实例化对象 ???????????this.preparedStatement = this.connection.prepareStatement(sql); ???????????// 设置id ???????????this.preparedStatement.setString(1, user.getUserid()); ???????????this.preparedStatement.setString(2, user.getPassword()); ???????????ResultSet resultset = this.preparedStatement.executeQuery(); ???????????if(resultset.next()){ ???????????????user.setName(resultset.getString(1)); ???????????????flag = true; ???????????} ???????}catch (Exception e){ ???????????throw ?e; ???????}finally { ???????????if(this.preparedStatement != null){ ???????????????try{ ???????????????????this.preparedStatement.close(); ???????????????}catch (Exception e){ ???????????????????throw ?e; ???????????????} ???????????} ???????} ???????return flag; ???}}

代理类

package com.ming.dao;import com.ming.dbc.DatabaseConnection;import com.ming.vo.User;public class UserDAOProxy implements IUserDAO { ???private DatabaseConnection databaseConnection = null; ???private IUserDAO dao = null; ???public UserDAOProxy(){ ???????try{ ???????????this.databaseConnection = new DatabaseConnection(); ???????}catch (Exception e){ ???????????e.printStackTrace(); ???????} ???????this.dao = new UserDAOImpl(this.databaseConnection.getConnection()); ???} ???/** ????* 用户登录验证 ????* ????* @param user 传入VO对象 ????* @return 验证操作结果 ????* @throws Exception 抛出错误 ????*/ ???@Override ???public boolean findLogin(User user) throws Exception { ???????boolean flag = false; ???????try{ ???????????flag = this.dao.findLogin(user); ???????}catch (Exception e){ ???????????throw ?e; ???????}finally { ???????????this.databaseConnection.close(); ???????} ???????return flag; ???}}

定义代理工厂

package com.ming.factory;import com.ming.dao.IUserDAO;import com.ming.dao.UserDAOProxy;public class DAOFactory { ???public static IUserDAO getIuserDAOInstance(){ ???????return new UserDAOProxy(); ???}}

实体关系映射

package com.ming.vo;// 对user表进行映射public class User { ???private String userid; ???private String name; ???private String password; ???public String getUserid() { ???????return userid; ???} ???public String getName() { ???????return name; ???} ???public String getPassword() { ???????return password; ???} ???public void setUserid(String userid) { ???????this.userid = userid; ???} ???public void setName(String name) { ???????this.name = name; ???} ???public void setPassword(String password) { ???????this.password = password; ???}}

视图层

<%@ page import="java.util.List" %><%@ page import="java.util.Iterator" %><%-- ?Created by IntelliJ IDEA. ?User: ming ?Date: 19-3-16 ?Time: 下午11:07 ?To change this template use File | Settings | File Templates.--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head> ???<title>Title</title></head><body><h2>用户登录程序</h2><% ???List<String> info = (List<String>)request.getAttribute("info"); ???if(info != null){ ???????Iterator<String> iterator = info.iterator(); ???????while(iterator.hasNext()){ ???????????%> ???????????????<h4><%=iterator.next()%></h4> ???????????<% ???????} ???}%><form action="loginServlet" method="post"> ???用户id <input type="text" name="userid" id="uname"/> ???密码 <input type="password" name="userpass" id="password"/> ???<input type="submit" value="登录" id="submit"/> ???<input type="reset" value="重置"/></form><script> ???let submit = document.getElementById("submit"); ???submit.onclick = (event) => { ???????let uname = document.getElementById("uname").value; ???????let password = document.getElementById("password").value; ???????if(!(/^\w{5,15}/.test(uname))){ ???????????alert("用户id为5-15位"); ???????????return false; ???????} ???????if(!(/^\w{5,15}/.test(password))){ ???????????alert("密码必须为5-15位"); ???????????return false; ???????} ???????return true; ???}</script></body></html>

配置文件

<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd" ><web-app> ?<display-name>Archetype Created Web Application</display-name> ???<servlet> ???????<servlet-name>login</servlet-name> ???????<servlet-class>com.ming.servlrt.LoginServlet</servlet-class> ???</servlet> ???<servlet-mapping> ???????<servlet-name>login</servlet-name> ???????<url-pattern>/loginServlet</url-pattern> ???</servlet-mapping></web-app>

mvc运行流程

表单提交到servlet,servlet调用dao进行表单验证,然后dao连接数据库进行验证,验证结果返回给业务层,即servlet,在业务层servlet中获取info等日志信息,然后服务器端跳转到运行结果页面即view层.

web开发模式

原文地址：https://www.cnblogs.com/melovemingming/p/10549887.html