认识什么是自定义MVC-阿里云开发者社区

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

MVC结构

Model：是应用程序中用于处理应用程序数据逻辑的部分，通常模型对象负责在数据库中存取数据。
View：是应用程序中处理数据显示的部分，通常视图是依据模型数据创建的。

Controller：是应用程序中处理用户交互的部分，通常控制器负责从视图读取数据，控制用户输入，并向模型发送数据。

2.我们为什么要用MVC

MVC是一个框架模式，它强制性的使应用程序的输入、处理和输出分开。使用MVC应用程序被分成三个核心部件：模型、视图、控制器。它们各自处理自己的任务。最典型的MVC就是JSP + servlet + javabean的模式

3.目标：

理解并熟悉自定义MVC框架工作原理

1.mvc框架定义

2.分析S阶段MVC框架的代码的组成及缺陷

组成

BookServlet:

package com.zhanghao.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 {
  this.doPost(req, resp);
}
@Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  String methodName = req.getParameter("methodName");
//  if ("add".equals(methodName)) {
//    add(req, resp);
//  }else if ("del".equals(methodName)) {
//    del(req,resp);
//  }else if("upd".equals(methodName)){
//    upd(req, resp);
//  }else if("list".equals(methodName)) {
//    list(req,resp);
//  }else if ("load".equals(methodName)) {
//    load(req,resp);
//  }
  try {
    Method m = this.getClass().getDeclaredMethod(methodName, HttpServletRequest.class,HttpServletResponse.class);
    m.setAccessible(true);
    m.invoke(this, req,resp);
  } catch (Exception e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
  }
}
private void load(HttpServletRequest req, HttpServletResponse resp) {
  // TODO Auto-generated method stub
}
private void list(HttpServletRequest req, HttpServletResponse resp) {
  System.out.println("BookaddServlet.lisy...");
}
private void upd(HttpServletRequest req, HttpServletResponse resp) {
  System.out.println("BookaddServlet.upd...");
}
private void del(HttpServletRequest req, HttpServletResponse resp) {
  System.out.println("BookaddServlet.del...");  
}
private void add(HttpServletRequest req, HttpServletResponse resp) {
  System.out.println("BookaddServlet.add...");
}
}

index.jsp

<%@ 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>
<p>版本1 </p>
弊端：每一张表对应的每一个操作，都要写一个servlet类来处理<hr>
<a href="bookAdd.action">增加</a>
<a href="bookDel.action">删除</a>
<a href="bookUpd.action">修改</a>
<a href="bookList.action">查询</a>
<p>版本2</p>
弊端：虽然每一张表对应的每一个操作，只要写一个servlet类来处理，但是每增加一个操作，都需要改变原有的代码块，换句话说就是增加条件分支<hr>
<a href="book.action?methodName=add">增加</a>
<a href="book.action?methodName=del">删除</a>
<a href="book.action?methodName=upd">修改</a>
<a href="book.action?methodName=list">查询</a>
<p>版本3</p>
弊端：虽然解决if条件分支代码冗余的问题，但是放到项目范围内，反射的代码是重复的<hr>
<a href="book.action?methodName=add">增加</a>
<a href="book.action?methodName=del">删除</a>
<a href="book.action?methodName=upd">修改</a>
<a href="book.action?methodName=list">查询</a>
<p>版本4</p>
<a href="book.action?methodName=add">增加</a>
<a href="book.action?methodName=del">删除</a>
<a href="book.action?methodName=upd">修改</a>
<a href="book.action?methodName=list">查询</a>
</body>
</html>

BookUpdServlet

package com.zhanghao.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("/bookUpd.action")
public class BookUpdServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  this.doPost(req, resp);
}
@Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  System.out.println("BookaddServlet.upd...");
} 
}

BookListServlet

package com.zhanghao.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("/bookList.action")
public class BookListServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  this.doPost(req, resp);
}
@Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  System.out.println("BookaddServlet.list...");
} 
}

BookDelServlet

package com.zhanghao.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("/bookDel.action")
public class BookDelServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  this.doPost(req, resp);
}
@Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  System.out.println("BookaddServlet.del...");
} 
}

BookAddServlet

package com.zhanghao.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("/bookAdd.action")
public class BookAddServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  this.doPost(req, resp);
}
@Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  System.out.println("BookaddServlet");
} 
}

BookAction

package com.zhanghao.web;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.zhanghao.framework.Action;
public class BookAction extends Action{
  public void add(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  System.out.println("BookaddServlet.add...");
  } 
  public void del(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    System.out.println("BookaddServlet.del...");
    }
  public void upd(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    System.out.println("BookaddServlet.upd...");
    }
  public void list(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    System.out.println("BookaddServlet.list...");
    }
}

DispatherServlet：

DispatherServlet 他就是中央控制器

package com.zhanghao.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.zhanghao.web.BookAction;
/**
 * 对应图中的ctionServlet:中央控制器
 * @author zhanghao
 *
 */
@WebServlet("*.action")
public class DispatherServlet extends HttpServlet{
  public Map<String,Action > actionMap=new HashMap<String, Action>();
  @Override
  public void init() throws ServletException {
    actionMap.put("/book", new BookAction());
  }
  @Override
  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    this.doPost(req, resp);
  }
  @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    String methodName = req.getParameter("methodName");
//    http://localhost:80/mvc/book.action?methodName=add
//    http://localhost:80/mvc/order.action?methodName=add
//    book -> BookAction -> action
    String uri = req.getRequestURI();
    uri=uri.substring(uri.lastIndexOf("/"),uri.indexOf("."));
    Action action = actionMap.get(uri);
    action.execute(req,resp);
  }
}

Action:子控制器

package com.zhanghao.framework;
import java.io.IOException;
import java.lang.reflect.Method;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * 子控制器
 * 真正做事，处理浏览器发送的请求的类
 * @author Administrator
 *
 */
public class Action {
  protected void execute(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  String methodName = req.getParameter("methodName");
  try {
    Method m = this.getClass().getDeclaredMethod(methodName, HttpServletRequest.class,HttpServletResponse.class);
    m.setAccessible(true);
    m.invoke(this, req,resp);
  } catch (Exception e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
  }
}
}

4.如何利用自定义MVC框架的思想优化S阶段的三层结构

三层架构是基于业务逻辑来分的，而MVC是基于页面来分的；
三层是种软件架构，通过接口实现编程，MVC模式是一种复合设计模式，一种解决方案；
三层架构模式是体系结构模式，MVC是设计模式；
三层架构模式又可归于部署模式，MVC可归于表示模式。

总结：

程序设计使用MVC等设计模式，最终目的就是达到天人合一的“高内聚，低耦合”，甚至零耦合

认识什么是自定义MVC

1.什么是MVC：

2.我们为什么要用MVC

3.目标：

1.mvc框架定义

2.分析S阶段MVC框架的代码的组成及缺陷

组成

BookServlet:

DispatherServlet：

Action:子控制器

4.如何利用自定义MVC框架的思想优化S阶段的三层结构

总结：

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