web开发模式

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

no
列名称
描述

1
userid
保存用户的登录 id

2
name
用户真实姓名

3
password
用户密码

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.