MVC初探

来源：互联网发布：mac gitignore文件编辑：程序博客网时间：2024/05/22 11:47

4个步骤：

①分析用户视图及高层体系结构

②创建用于开发这个项目的开发环境

③创建用于部署这个项目的部署环境

④对各个组件完成迭代的开发和测试

用户视图

form.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><h1 align="center">Beer Selection Page</h1><form method="post"action="SelectBeer.do">Select beer characteristics<p>Color:<select name="color" size="1"><option>light<option>amber<option>brown<option>dark</select><br><br><center><input type="SUBMIt"></center></form></body></html>

result.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"    pageEncoding="ISO-8859-1"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><%@ page import="java.util.*" %><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title></title></head><body><h1 align="center">Beer Recommendations JSP</h1><p><%List styles = (List)request.getAttribute("styles");Iterator it = styles.iterator();while(it.hasNext()){out.print("<br>try: "+it.next());}%></body></html>

体系结构：

1）用户请求得到form.html页面

2）容器获得form.html页面

3）容器把这个页面返回给浏览器，用户再在浏览器上回答表单上的问题

4）浏览器把请求数据发给容器

5）容器根据URL找到正确的servlet，并把请求传递给这个servlet

6）servlet调用BeerExpert寻求帮助

7）这个“专家”类返回一个回答，servlet把这个回答增加到请求对象

8）servlet把请求转发给JSP

9）JSP从请求对象得到回答

10）JSP为容器生成一个页面

11）容器把这个页面返回给用户

开发环境

配置文件

web.xml

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.4">  <servlet>    <servlet-name>Ch3 Beer</servlet-name>    <servlet-class>com.example.web.BeerSelect</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>Ch3 Beer</servlet-name>    <url-pattern>/SelectBeer.do</url-pattern>  </servlet-mapping></web-app>

模型

BeerExpert.java

package com.example.model;import java.util.ArrayList;import java.util.List;public class BeerExpert {public List getBrands(String color){List brands = new ArrayList();if(color.equals("amber")){brands.add("Jack Amber");brands.add("Red Moose");}else{brands.add("Jail Pale Ale");brands.add("Gout Stout");}return (brands);}}

控制器

BeerSelect.java

package com.example.web;import java.io.IOException;import java.io.PrintWriter;import java.util.Iterator;import java.util.List;import javax.servlet.RequestDispatcher;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 com.example.model.BeerExpert;/** * Servlet implementation class BeerSelect */@WebServlet("/BeerSelect")public class BeerSelect extends HttpServlet {private static final long serialVersionUID = 1L;           /**     * @see HttpServlet#HttpServlet()     */    public BeerSelect() {        super();        // TODO Auto-generated constructor stub    }/** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub}/** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//这个方法来自ServletResponse接口//response.setContentType("text/html");//PrintWriter out = response.getWriter();//out.println("Beer Selection Advice<br>");//这个方法来自ServletRequest接口。参数与html<select>标记中name属性值一致String c = request.getParameter("color");//测试结果显示//out.println("<br>Got beer color "+c);BeerExpert be = new BeerExpert();List result = be.getBrands(c);//为请求对象添加一个属性，供jsp使用。jsp要寻找stylesrequest.setAttribute("styles", result);//为jsp实例化一个请求分派器RequestDispatcher view = request.getRequestDispatcher("result.jsp");//使用请求分派器要求容器准备好jsp，并向jsp发送请求和响应view.forward(request, response);}}

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