摘要：顯示層控制層數據層統一交給或者處理處理流程客戶端發送到執行讀取返回返回給在返回給在給客戶端問題代碼雜亂即方式客戶端發送到然后執行用于讀取控制器獲取到讀取的數據以后再次返回給生成文件給客戶端分為顯示層控制層模型層屬于提供的分布式組件服務分

顯示層,控制層,數據層,統一交給jsp或者javabean處理.

客戶端發送request 到 jsp jsp 執行javabean javabean讀取databases

返回 databases 返回給javabean 在返回給jsp 在response 給客戶端

代碼雜亂
即 jsp + dao 方式

客戶端發送request 到servlet 然后servlet 執行javabean javabean用于讀取databases 控制器,獲取到javabean讀取的數據以后,再次返回給jsp,jso生成html文件,response 給客戶端
分為 顯示層 控制層 模型層

EJB 屬于SUN提供的分布式組件服務 分為會話bean 實體bean 消息驅動bean

一個登錄程序
用戶提交登錄信息,發送給servlet servlet數據驗證失敗將會返回給登錄頁,同時servlet將會調用數據層操作dao,dao到數據庫databases進行驗證,結果返回給servlet 然后返回兩個結果,登錄成功,登錄失敗.

![](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;
    // 連接數據庫
    public DatabaseConnection() throws Exception{
        try{
            Class.forName(DBDRIVER);
            connection = DriverManager.getConnection(DBURL, DBUSER, DBPASSWORD);
        }catch (Exception e){
            throw e;
        }
    }
    // 獲得數據庫連接
    public Connection getConnection(){
        return this.connection;
    }
    // 數據庫關閉
    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 {
    /**
     * 用戶登錄驗證
     * @param user 傳入VO對象
     * @return 驗證操作結果
     * @throws Exception 拋出錯誤
     */
    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 {
    // 數據庫連接對象
    private Connection connection = null;
    // 操作對象
    private PreparedStatement preparedStatement = null;
    // 數據庫連接
    public UserDAOImpl(Connection _connection){
        this.connection = _connection;
    }
    /**
     * 用戶登錄驗證
     *
     * @param user 傳入VO對象
     * @return 驗證操作結果
     * @throws Exception 拋出錯誤
     */
    @Override
    public boolean findLogin(User user) throws Exception {
        boolean flag = false;
        try{
            String sql = "SELECT name FROM user WHERE userid = ? AND password = ?";
            // 獲得實例化對象
            this.preparedStatement = this.connection.prepareStatement(sql);
            // 設置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());
    }
    /**
     * 用戶登錄驗證
     *
     * @param user 傳入VO對象
     * @return 驗證操作結果
     * @throws Exception 拋出錯誤
     */
    @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;

// 對user表進行映射
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" %>


    


用戶登錄程序
<%
    List info = (List)request.getAttribute("info");
    if(info != null){
        Iterator iterator = info.iterator();
        while(iterator.hasNext()){
            %>
                
<%=iterator.next()%>
            <%
        }
    }
%>

    用戶id 
    密碼 
    
    

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

表單提交到servlet,servlet調用dao進行表單驗證,然后dao連接數據庫進行驗證,驗證結果返回給業務層,即servlet,在業務層servlet中獲取info等日志信息,然后服務器端跳轉到運行結果頁面即view層.