java_MVC三层架构

1、mvc的概述

MVC是Model-View-Controller的简称即模型 - 视图 - 控制器

model:(模型)

1、模型是应用程序的主体部分，模型表示业务数据和业务逻辑

2、一个模型能为多个视图提供数据

3、由于应用于模型的代码只需写一次就可以被多个视图重用，所有提高了代码的可重用性

view:（视图）

视图是用户看到并与之交互的界面作用如下:

1.视图向用户显示相关的数据

2.接收用户的输入

3.不进行任何实际的业务处理

controller:（控制器)

1.控制器接收用户的输入并调用模型和视图去完成用户的需求

2.控制器接收请求并确定调用哪个模型组件去处理请求，然后确定哪个视图来显示模型处理返回的数据

实例：

JavaEE_MVC案例（模糊查询）

需要的jar包

DbUtils数据库连接工具

c3p0连接池

mysql.jdbc

所需的jar

在项目中创建一个名为com.it999.mvcapp的包有几个文件夹

dao

domain

dao.impl

servlet

包结构

正文：

index.jsp中编程一个超链接

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

<title>JAVAMVC模糊查询</title>

</head>

<body>

</body>

</html>

user.java 作为一个数据模块

package com.it999.javaMvc;

public class User {

private Integer id;

private String addname;

private String addId;

private String addP;

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

public String getAddname() {

return addname;

}

public void setAddname(String addname) {

this.addname = addname;

}

public String getAddId() {

return addId;

}

public void setAddId(String addId) {

this.addId = addId;

}

public String getAddP() {

return addP;

}

public void setAddP(String addP) {

this.addP = addP;

}

//构造函数

public User(Integer id, String addname, String addId, String addP) {

this.id = id;

this.addname = addname;

this.addId = addId;

this.addP = addP;

}

//空构造函数

public User(){}

}

[3] UserDao.java 作为连接数据库的模块

package com.it999.javaMvc;

import java.sql.*;

import java.util.ArrayList;

import java.util.List;

public class UserDao {

public List<User> getAll(){

//定义一个集合用来管理user数据

List<User> users = new ArrayList<User>();

Connection connection = null;

PreparedStatement preparedStatement = null;

ResultSet resultSet = null;

try {

//设置mysql驱动连接路径唯一格式

String Driver = "com.mysql.jdbc.Driver";

//连接mysql的路径

String url = "jdbc:mysql://localhost:3306/day30";

//数据库用户名

String user = "root";

//数据库密码

String password = "zan980708...";

//注册驱动

Class.forName(Driver);

//连接数据库

connection = DriverManager.getConnection(url, user, password);

//mysql 查询语句

String sql = "SELECT id,addname,addId,addP From adduser";

//查询数据

preparedStatement = connection.prepareStatement(sql);

//查询

resultSet = preparedStatement.executeQuery();

//遍历resultSet集合的值

while(resultSet.next()){

int id = resultSet.getInt(1);

String addname = resultSet.getString(2);

String addId = resultSet.getString(3);

String addP = resultSet.getString(4);

//放入到user中

User user1 = new User(id,addname,addId,addP);

//把查询的user放入的list<User>集合中

users.add(user1);

}

}catch (Exception e){

e.printStackTrace();

}finally {

if(resultSet != null){

try {

resultSet.close();

} catch (SQLException e) {

e.printStackTrace();

}

if(preparedStatement != null){

try {

preparedStatement.close();

} catch (SQLException e) {

e.printStackTrace();

}

if(connection != null){

try {

connection.close();

} catch (SQLException e) {

e.printStackTrace();

}

return users;

}

[4] UserServlet.java 作为index.jsp中请求的servlet

package com.it999.javaMvc;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

@WebServlet(name = "userServlet")

public class UserServlet extends HttpServlet {

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

System.out.println("来了");

//创建userDao对象

UserDao userDao = new UserDao();

//调用userDao中的getAll()方法

List<User> users = userDao.getAll();

//设置Attribute的值

request.setAttribute("users",users);

//设置转发路径使用forward()方法转发

request.getRequestDispatcher("/user.jsp").forward(request,response);

}

user.jsp 作为转发的页面

<%@ page import="com.it999.javaMvc.User" %>

<%@ page import="java.util.List" %>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

</head>

<body>

List<User> userList = (List<User>)request.getAttribute("users");

<table>

<tr>

<th>addname</th>

<th>addId</th>

</tr>

<% for (User user : userList){%>

<tr>

</tr>

<% }%>

</table>

</body>

</html>

[6] web.xml 作为配置项

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"

version="4.0">

<servlet-name>userServlet</servlet-name>

<servlet-class>com.it999.javaMvc.UserServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>userServlet</servlet-name>

<url-pattern>/userServlet</url-pattern>

</servlet-mapping>

</web-app>