目录

一、MVC简介

二、最初的增删改查

三、反射版的增删改查

四、自定义MVC工作原理图

五、自定义MVC后台代码实现

一、MVC简介

   1、什么是MVC？

            MVC的全名是Model View Controller，是模型(model)－视图(view)－控制器(controller)的缩写，是一种软件设计典范。它是用一种业务逻辑、数据与界面显示分离的方法来组织代码，将众多的业务逻辑聚集到一个部件里面，在需要改进和个性化定制界面及用户交互的同时，不需要重新编写业务逻辑，达到减少编码的时间。

    2、MVC的好处

        视图层和业务层分离，这样就允许更改视图层代码而不用重新编译模型和控制器代码，同样，一个应用的业务流程或者业务规则的改变只需要改动MVC的模型层即可。因为模型与控制器和视图相分离，所以很容易改变应用程序的数据层和业务规则。

---

二、最初的增删改查

       jsp界面

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







目前增删改查的方法
增加
删除
修改
查询

删除的Servlet

package com.zwc.web;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/book/del")
public class DelBookServlet 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 {
		System.out.println("处理书籍的删除业务，调用bookbiz");
	}
}

 增加Servlet

package com.zwc.web;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/book/list")
public class AddBookServlet 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 {
		System.out.println("处理书籍的查询业务，调用bookbiz");
	}
}

修改Servlet

package com.zwc.web;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/book/edit")
public class EditBookServlet 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 {
		System.out.println("处理书籍的修改业务，调用bookbiz");
	}
}

查询Servlet 

package com.zwc.web;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/book/add")
public class ListBookServlet 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 {
		System.out.println("处理书籍的增加业务，调用bookbiz");
	}
}

界面效果

点击标签控制台弹出对应的Servlet

 

 

 从最初的增删改查可以看到问题：

      1、 如果关于单个实体/表操作场景越多，需要新建的类也就越多，也就造成了项目中类的数量过于庞大

三、反射版的增删改查

               jsp界面：

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







目前增删改查的方法
增加
删除
修改
查询

类数量过多问题的优化
增加
删除
修改
查询
回显

新建一个BookServlet

package com.zwc.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;
@WebServlet("/book.action")
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 {
//		为了区分当前请求的目的，增删改查的目的，就从前台将要调用的方法名传递到后台
		String methodName = req.getParameter("methodName");
//	
		if("add".equals(methodName)) {
//			如果前台传递到后台的是一个新增的请求，那么后台就调用新增方法
			add(req,resp);
		}
		else if("del".equals(methodName)) {
			del(req,resp);
		}
		else if("edit".equals(methodName)) {
			edit(req,resp);
		}
		else if("list".equals(methodName)) {
			list(req,resp);
		}
	}

	private void list(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用list方法");
		
	}

	private void edit(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用edit方法");
	}

	private void del(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用del方法");	
	}

	private void add(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用add方法");
	}
	private void load(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用load方法");
	}
}

运行结果

 

在上面又有一个问题：

2、当新增了业务，除了要添加该业务对应的方法（load），同时还要改动原有的方法

所以我们在这里优化BookServlet：

package com.zwc.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;
@WebServlet("/book.action")
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 {
//		为了区分当前请求的目的，增删改查的目的，就从前台将要调用的方法名传递到后台
		String methodName = req.getParameter("methodName");
//		methodName可以是add/del/list/edit/.....
//		前台传递上面方法，就调用当前类的对应方法
		try {
			Method m = this.getClass()//BookSerlvet.class
				.getDeclaredMethod(methodName, HttpServletRequest.class,HttpServletResponse.class);
			m.setAccessible(true);
//			调用当前类实例的methodName 方法
			m.invoke(this, req,resp);
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}

	private void list(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用list方法");
		
	}

	private void edit(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用edit方法");
	}

	private void del(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用del方法");	
	}

	private void add(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用add方法");
	}
	private void load(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用load方法");
	}
}

同样测试运行:

若我们在增加一个订单的增删改查，同样写一个orderServlet

 

我们可以观察到

 3、反射相关代码、在每一个实体类对应的Servlet中都存在
 4、每一个Servlets中都有doget、dopost

四、自定义MVC工作原理图

 

五、自定义MVC后台代码实现

先创建中央控制器：
主要职能：接受浏览器请求，找到对应的处理人

package com.zwc.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.zwc.web.BookAction;


@WebServlet("*.action")
public class DispatcherServlet extends HttpServlet{
	private Map actions = new HashMap();
	
//	程序启动时，只会加载一次
	@Override
	public void init() throws ServletException {
		actions.put("/book",new BookAction());
		actions.put("/order",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 {
		//http://localhost:8080/mvc/book.action?methodName=list
		String uri = req.getRequestURI();
//		要拿到book，最后一个/到最后一个.为止
		 uri = uri.substring(uri.lastIndexOf("/"), uri.lastIndexOf("."));
		 Action action = actions.get(uri);
		 action.execute(req, resp);
	}
}

在创建一个子控制器，对应请求的处理人

package com.zwc.framework;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public interface Action {
	void execute(HttpServletRequest req, HttpServletResponse resp); 
}

实现子控制器接口 

package com.zwc.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) {
//		为了区分当前请求的目的，增删改查的目的，就从前台将要调用的方法名传递到后台
		String methodName = req.getParameter("methodName");
//		methodName可以是add/del/list/edit/.....
//		前台传递上面方法，就调用当前类的对应方法
		try {
			Method m = this.getClass()//BookSerlvet.class
				.getDeclaredMethod(methodName, HttpServletRequest.class,HttpServletResponse.class);
			m.setAccessible(true);
//			调用当前类实例的methodName 方法
			m.invoke(this, req,resp);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

}

继承实现子控制器的接口

package com.zwc.web;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.zwc.framework.Action;
import com.zwc.framework.ActionSupport;

public class BookAction extends ActionSupport{

	private void list(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用list方法");
		
	}

	private void edit(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用edit方法");
	}

	private void del(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用del方法");	
	}

	private void add(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用add方法");
	}
	private void load(HttpServletRequest req, HttpServletResponse resp) {
		System.out.println("在同样一个Servlet中调用load方法");
	}

}

运行结果：