MVC框架自定义实现过程

1、思维导图

2、什么是MVC？

MVC全名是Model View Controller，是模型(model)－视图(view)－控制器(controller)的缩写， 它是一种软件设计典范，用一种业务逻辑、数据、界面显示分离的方法组织代码。

3、运行原理

用户发送请求 → 中央控制器接受用户请求 → 分析请求连接/获取到用户需要的类+方法 → 调用相对应的Model → 访问数据库服务器

4、演绎过程

4.1.控制层

BookServlet：

package com.tyf.web;
import java.io.IOException;
import java.lang.reflect.Method;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class BookServlet extends HttpServlet {
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doPost(req, resp);
	}
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		/**
		 * 增删改查缺陷:
		 * 		当需求发送改变，或者新增需求的时候，需要改动下面代码
		 *
		 * 解决方案:
		 * 		前台传递name到后台，实际就是想要调用当前(this)类对象的name方法
		 */
		String name = req.getParameter("name");
		try {
			Method m = this.getClass().getDeclaredMethod(name, HttpServletRequest.class,HttpServletResponse.class);
			m.setAccessible(true);
			m.invoke(this, req,resp);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		/*if ("add".equals(name)) {
			add(req,resp);
		}else if ("delete".equals(name)) {
			delete(req,resp);
		}else if ("edit".equals(name)) {
			edit(req,resp);
		}else if ("list".equals(name)) {
			list(req,resp);
		}else if ("load".equals(name)) {
			load(req,resp);
		}*/
	}
｝

DispatchServlet：

package com.tyf.framework;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
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.tyf.web.BookAction;
/**
 *
 * 目标：
 * 	根据自定义mvc框架的原理图  完成框架的研发
 * @author Tang  中央控制器
 * 	寻找子控制器
 *
 * 2021年8月30日  下午6:49:35
 */

@WebServlet("*.action")
public class DispatchServlet extends HttpServlet {
	//存放子控制器的容器
	private Map<String , ActionSupport> actions = new HashMap<String , ActionSupport>();
	//初始化子控制器容器(集合),经过初始化,action容器内部就有了子控制器
	//init(初始化方法),service(服务),destroy(销毁)
	@Override
	public void init() throws ServletException {
		actions.put("/book", new BookAction());
	}
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doPost(req, resp);
	}
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		//完成子控制器对的过程
		//浏览器:http://localhost:8080/J2ee12/book.action?name=add
		//目标:BookAction.add()...
		/**
		 * 思路:
		 * 	1.从浏览器URL中获取到"/book"字符串
		 * 	2.在子控制器中拿到BookAction
		 * 	3.BookAction.add()
		 */
		String url = req.getRequestURI();
		url = url.substring(url.lastIndexOf("/"), url.lastIndexOf("."));
		//action=BookAction
		ActionSupport action = actions.get(url);
		action.execute(req, resp);
	}
}

4.2.模型层

ActionSupport：

package com.tyf.framework;
import java.lang.reflect.Method;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ActionSupport implements Action {
 	@Override
	public void execute(HttpServletRequest req, HttpServletResponse resp) {
		String name = req.getParameter("name");
		try {
			Method m = this.getClass().getDeclaredMethod(name, HttpServletRequest.class,HttpServletResponse.class);
			m.setAccessible(true);
			m.invoke(this, req,resp);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

DispatchServlet：

package com.tyf.framework;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
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.tyf.web.BookAction;
/**
 *
 * 目标：
 * 	根据自定义mvc框架的原理图  完成框架的研发
 *
 *
 * @author Tang  中央控制器
 * 	寻找子控制器
 *
 * 2021年8月30日  下午6:49:35
 */
@WebServlet("*.action")
public class DispatchServlet extends HttpServlet {
	//存放子控制器的容器
	private Map<String , ActionSupport> actions = new HashMap<String , ActionSupport>();
	//初始化子控制器容器(集合),经过初始化,action容器内部就有了子控制器
	//init(初始化方法),service(服务),destroy(销毁)
	@Override
	public void init() throws ServletException {
		actions.put("/book", new BookAction());
	}
 	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doPost(req, resp);
	}
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		//完成子控制器对的过程
		//浏览器:http://localhost:8080/J2ee12/book.action?name=add
		//目标:BookAction.add()...
		/**
		 * 思路:
		 * 	1.从浏览器URL中获取到"/book"字符串
		 * 	2.在子控制器中拿到BookAction
		 * 	3.BookAction.add()
		 */
		String url = req.getRequestURI();
		url = url.substring(url.lastIndexOf("/"), url.lastIndexOf("."));
		//action=BookAction
		ActionSupport action = actions.get(url);
		action.execute(req, resp);
	}
}

4.3视图层

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!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>
	目前多数人增删改查的代码:
		<a href="${pageContext.request.contextPath}/book/add" rel="external nofollow" >增加</a>
		<a href="${pageContext.request.contextPath}/book/delete" rel="external nofollow" >删除</a>
		<a href="${pageContext.request.contextPath}/book/edit" rel="external nofollow" >修改</a>
		<a href="${pageContext.request.contextPath}/book/list" rel="external nofollow" >查询</a>
	<hr>
	增删改查的代码2.0
		<a href="${pageContext.request.contextPath}/book.action?name=add" rel="external nofollow" >增加</a>
		<a href="${pageContext.request.contextPath}/book.action?name=delete" rel="external nofollow" >删除</a>
		<a href="${pageContext.request.contextPath}/book.action?name=edit" rel="external nofollow" >修改</a>
		<a href="${pageContext.request.contextPath}/book.action?name=list" rel="external nofollow" >查询</a>
	<hr>
	增删改查的代码3.0
		<a href="${pageContext.request.contextPath}/book.action?name=load" rel="external nofollow" >回显</a>
		<a href="${pageContext.request.contextPath}/book.action?name=ref" rel="external nofollow" >关联</a>

</body>
</html>

5、运行结果

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