web开发模式

摘要：显示层控制层数据层统一交给或者处理处理流程客户端发送到执行读取返回返回给在返回给在给客户端问题代码杂乱即方式客户端发送到然后执行用于读取控制器获取到读取的数据以后再次返回给生成文件给客户端分为显示层控制层模型层属于提供的分布式组件服务分

显示层,控制层,数据层,统一交给jsp或者javabean处理.

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

代码杂乱
即 jsp + dao 方式

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

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.

![](https://melovemingming-125387...
)

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;
            }
        }
    }
}

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;
}

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;
    }
}

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;
    }
}

package com.ming.factory;

import com.ming.dao.IUserDAO;
import com.ming.dao.UserDAOProxy;

public class DAOFactory {
    public static IUserDAO getIuserDAOInstance(){
        return new UserDAOProxy();
    }
}

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;
    }
}

<%@ 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" %>


    


用户登录程序
<%
    List info = (List)request.getAttribute("info");
    if(info != null){
        Iterator iterator = info.iterator();
        while(iterator.hasNext()){
            %>
                
<%=iterator.next()%>
            <%
        }
    }
%>

    用户id 
    密码 
    
    

  Archetype Created Web Application
    
        login
        com.ming.servlrt.LoginServlet
    
    
        login
        /loginServlet
    

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.