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>