• 自定义MVC

    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(Model View Controller)是一种软件设计的框架模式，它采用模型(Model)-视图(View)-控制器(controller)的方法把业务逻辑、数据与界面显示分离。把众多的业务逻辑聚集到一个部件里面，当然这种比较官方的解释是不能让我们足够清晰的理解什么是MVC的。用通俗的话来讲，MVC的理念就是把数据处理、数据展示(界面)和程序/用户的交互三者分离开的一种编程模式

    2.mvc的作用

    MVC 属架构于模式的一种，所谓架构就是如何设计一个程序的结构。MVC 将程序结构划分为三层，每一层都对外提供了可供上层调用的接口，既能维系三层之间的联系，也能保持相对的独立性

    二，最初的增删改查 

    jsp界面：

    1. <%@ page language="java" contentType="text/html; charset=UTF-8"
    2.     pageEncoding="UTF-8"%>
    3. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    4. <html>
    5. <head>
    6. <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    7. <title>测试界面</title>
    8. </head>
    9. <body>
    10.  
    11. <h3>目前增删改查的方法</h3>
    12. <a href="${pageContext.request.contextPath }/book/add">增加</a>
    13. <a href="${pageContext.request.contextPath }/book/del">删除</a>
    14. <a href="${pageContext.request.contextPath }/book/edit">修改</a>
    15. <a href="${pageContext.request.contextPath }/book/list">查看</a>
    16.  
    17. </body>
    18. </html>

    增加servlet

    1. package com.ruojuan.web;
    2.  
    3. import java.io.IOException;
    4. import javax.servlet.ServletException;
    5. import javax.servlet.annotation.WebServlet;
    6. import javax.servlet.http.HttpServlet;
    7. import javax.servlet.http.HttpServletRequest;
    8. import javax.servlet.http.HttpServletResponse;
    9.  
    10. @WebServlet("/book/add")
    11. public class AddBookServlet extends HttpServlet {
    12. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    13. 		doPost(request, response);
    14. 	}
    15.  
    16. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    17. 		System.out.println("处理书籍的add业务，调用BookBiz");
    18. 	}
    19.  
    20. }

    删除servlet

    1. package com.ruojuan.web;
    2.  
    3. import java.io.IOException;
    4. import javax.servlet.ServletException;
    5. import javax.servlet.annotation.WebServlet;
    6. import javax.servlet.http.HttpServlet;
    7. import javax.servlet.http.HttpServletRequest;
    8. import javax.servlet.http.HttpServletResponse;
    9.  
    10. @WebServlet("/book/del")
    11. public class DelBookServlet extends HttpServlet {
    12. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    13. 		doPost(request, response);
    14. 	}
    15.  
    16. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    17. 		System.out.println("处理书籍的delete业务，调用BookBiz");
    18. 	}
    19.  
    20. }

    修改servlet

    1. package com.ruojuan.web;
    2.  
    3. import java.io.IOException;
    4. import javax.servlet.ServletException;
    5. import javax.servlet.annotation.WebServlet;
    6. import javax.servlet.http.HttpServlet;
    7. import javax.servlet.http.HttpServletRequest;
    8. import javax.servlet.http.HttpServletResponse;
    9.  
    10. @WebServlet("/book/edit")
    11. public class EditBookServlet extends HttpServlet {
    12. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    13. 		doPost(request, response);
    14. 	}
    15.  
    16. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    17. 		System.out.println("处理书籍的Edit业务，调用BookBiz");
    18. 	}
    19.  
    20. }

    查询servlet

    1. package com.ruojuan.web;
    2.  
    3. import java.io.IOException;
    4.  
    5. import javax.servlet.ServletException;
    6. import javax.servlet.annotation.WebServlet;
    7. import javax.servlet.http.HttpServlet;
    8. import javax.servlet.http.HttpServletRequest;
    9. import javax.servlet.http.HttpServletResponse;
    10.  
    11. @WebServlet("/book/list")
    12. public class ListBookServlet extends HttpServlet{
    13.  
    14. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    15. 		doPost(request, response);
    16. 	}
    17.  
    18. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    19. 		System.out.println("处理书籍的List业务，调用BookBiz");
    20. 	}
    21. 	
    22. }

    效果图：

    点击标签对应该标签的servlet功能

    存在的问题：
            1.关于单个实体/表操作场景越多，需要新建的类也就越多，造成了项目中的数量过于庞大
             2.当新增了业务，除了要添加该业务对应的方法load，同时还要改动源代码
            3.反射相关代码，在每一个实体类对应的servlet中存在
            4.每一个servlet中都有doget，dopost方法

    三，反射版的增删改查

    jsp界面：

    1. <%@ page language="java" contentType="text/html; charset=UTF-8"
    2.     pageEncoding="UTF-8"%>
    3. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    4. <html>
    5. <head>
    6. <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    7. <title>测试界面</title>
    8. </head>
    9. <body>
    10.  
    11. <h3>目前增删改查的方法</h3>
    12. <a href="${pageContext.request.contextPath }/book/add">增加</a>
    13. <a href="${pageContext.request.contextPath }/book/del">删除</a>
    14. <a href="${pageContext.request.contextPath }/book/edit">修改</a>
    15. <a href="${pageContext.request.contextPath }/book/list">查看</a>
    16.  
    17. <!-- 
    18. 	上述问题：
    19. 		1.关于单个实体/表操作场景越多，需要新建的类也就越多，造成了项目中的数量过于庞大
    20.  		2.当新增了业务，除了要添加该业务对应的方法load，同时还要改动源代码
    21. 		3.反射相关代码，在每一个实体类对应的servlet中存在
    22. 		4.每一个servlet中都有doget，dopost方法
    24.   -->
    25. <h3>类数量过多问题的优化</h3>
    26. <a href="${pageContext.request.contextPath }/book.action?methodName=add">增加</a>
    27. <a href="${pageContext.request.contextPath }/book.action?methodName=del">删除</a>
    28. <a href="${pageContext.request.contextPath }/book.action?methodName=edit">修改</a>
    29. <a href="${pageContext.request.contextPath }/book.action?methodName=list">查看</a>
    30. <a href="${pageContext.request.contextPath }/book.action?methodName=load">加载</a>
    31.  
    32.  
    33.  
    34. </body>
    35. </html>

    一个servlet具备多个功能:

    1. package com.ruojuan.web;
    2.  
    3. import java.io.IOException;
    4. import java.lang.reflect.Method;
    5.  
    6. import javax.servlet.ServletException;
    7. import javax.servlet.annotation.WebServlet;
    8. import javax.servlet.http.HttpServlet;
    9. import javax.servlet.http.HttpServletRequest;
    10. import javax.servlet.http.HttpServletResponse;
    11.  
    12. /**
    13.  * Servlet implementation class BookServlet
    14.  */
    15. @WebServlet("/book.action")
    16. public class BookServlet extends HttpServlet {
    17. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    18. 		doPost(request, response);
    19. 	}
    20.  
    21. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    22. 		 //未来区分当前请求的目的，增删改查的目的，就从前台讲要调用的方法名传递到后台
    23. 		String methodName = request.getParameter("methodName");
    24. 		//methodName可能是add/del/edit/list/load/xxx/...
    25. 		//前台传递什么方法，就调用当前类的方法
    26. 		try {
    27. 			Method m = this.getClass().getDeclaredMethod(methodName, HttpServletRequest.class,HttpServletResponse.class);
    28. 			m.setAccessible(true);
    29. 			m.invoke(this, request,response);
    30. 		} catch (Exception e) {
    31. 			e.printStackTrace();
    32. 		}
    33. 		
    34. 		
    35. 		
    36. 	}
    37.  
    38. 	private void load(HttpServletRequest request, HttpServletResponse response) {
    39. 		System.out.println("在同一个servlet中调用load方法");
    40. 		
    41. 	}
    42.  
    43. 	private void list(HttpServletRequest request, HttpServletResponse response) {
    44. 		System.out.println("在同一个servlet中调用list方法");
    45. 		
    46. 	}
    47.  
    48. 	private void edit(HttpServletRequest request, HttpServletResponse response) {
    49. 		System.out.println("在同一个servlet中调用edit方法");
    50. 		
    51. 	}
    52.  
    53. 	private void del(HttpServletRequest request, HttpServletResponse response) {
    54. 		System.out.println("在同一个servlet中调用del方法");
    55. 		
    56. 	}
    57.  
    58. 	private void add(HttpServletRequest request, HttpServletResponse response) {
    59. 		System.out.println("在同一个servlet中调用add方法");
    60. 		
    61. 	}
    62.  
    63. }

    效果图：

     

     四，自定义MVC工作原理图

     

     五，自定义mvc后台代码实现

    中央控制器：

    1. package com.ruojuan.framework;
    2.  
    3. import java.io.IOException;
    4. import java.util.HashMap;
    5. import java.util.Map;
    6.  
    7. import javax.servlet.ServletException;
    8. import javax.servlet.annotation.WebServlet;
    9. import javax.servlet.http.HttpServlet;
    10. import javax.servlet.http.HttpServletRequest;
    11. import javax.servlet.http.HttpServletResponse;
    12.  
    13. import com.ruojuan.web.BookAction;
    14.  
    15. /**
    16.  * 中央控制器
    17.  * 		主要职能：接受浏览器请求，找到对应的处理人
    18.  * @author liuruojuan
    19.  *
    20.  * 时间：2022年6月24日下午6:21:20
    21.  */
    22. @WebServlet("*.action")
    23. public class DispatcherServlet extends HttpServlet{
    24.  
    25. 	private Map<String, Action> actions = new HashMap<String, Action>();
    26. 	
    27. 	//程序启动时，只会加载一次
    28. 	
    29. 	
    30. 	@Override
    31. 	public void init() throws ServletException {
    32. 		actions.put("/book", new BookAction());
    33. //		actions.put("/book", new BookAction());
    34. 	}
    35.  
    36. 	@Override
    37. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    38. 		doPost(request, response);
    39. 	}
    40. 	
    41. 	@Override
    42. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    43. 		// TODO Auto-generated method stub
    44. 		String uri = request.getRequestURI();
    45. 		//要拿到/book,就是最后一个/到最后一个，的位子
    46. 		 uri = uri.substring(uri.lastIndexOf("/"),uri.lastIndexOf("."));
    47. 		
    48. 		 Action action = actions.get(uri);
    49. 		 action.execute(request, response);
    50. 	}
    51. 	
    52. 	
    53. }

    子控制器：

    1. package com.ruojuan.framework;
    2.  
    3. import java.io.IOException;
    4.  
    5. import javax.servlet.ServletException;
    6. import javax.servlet.http.HttpServletRequest;
    7. import javax.servlet.http.HttpServletResponse;
    8.  
    9. /**
    10.  * 子控制器：
    11.  * 		对应请求的控制人
    12.  * @author liuruojuan
    13.  *
    14.  * 时间：2022年6月24日下午6:22:51
    15.  */
    16. public interface Action {
    17. 	void execute(HttpServletRequest request, HttpServletResponse response) ;
    18.  
    19. }

    实现子控制器接口：

    1. package com.ruojuan.framework;
    2.  
    3. import java.io.IOException;
    4. import java.lang.reflect.Method;
    5.  
    6. import javax.servlet.ServletException;
    7. import javax.servlet.http.HttpServletRequest;
    8. import javax.servlet.http.HttpServletResponse;
    9.  
    10. public class ActionSupport implements Action {
    11.  
    12. 	@Override
    13. 	public void execute(HttpServletRequest request, HttpServletResponse response) {
    14. 		 //未来区分当前请求的目的，增删改查的目的，就从前台讲要调用的方法名传递到后台
    15. 		String methodName = request.getParameter("methodName");
    16. 		//methodName可能是add/del/edit/list/load/xxx/...
    17. 		//前台传递什么方法，就调用当前类的方法
    18. 		try {
    19. 			Method m = this.getClass().getDeclaredMethod(methodName, HttpServletRequest.class,HttpServletResponse.class);
    20. 			m.setAccessible(true);
    21. 			m.invoke(this, request,response);
    22. 		} catch (Exception e) {
    23. 			e.printStackTrace();
    24. 		}
    25. 		
    26. 	}
    27.  
    28. }

    继承子控制器实现的接口：

    1. package com.ruojuan.web;
    2.  
    3. import java.io.IOException;
    4.  
    5. import javax.servlet.ServletException;
    6. import javax.servlet.http.HttpServletRequest;
    7. import javax.servlet.http.HttpServletResponse;
    8.  
    9. import com.ruojuan.framework.Action;
    10. import com.ruojuan.framework.ActionSupport;
    11.  
    12. public class BookAction extends ActionSupport{
    13.  
    14. 	private void load(HttpServletRequest request, HttpServletResponse response) {
    15. 		System.out.println("在同一个servlet中调用load方法");
    16. 		
    17. 	}
    18.  
    19. 	private void list(HttpServletRequest request, HttpServletResponse response) {
    20. 		System.out.println("在同一个servlet中调用list方法");
    21. 		
    22. 	}
    23.  
    24. 	private void edit(HttpServletRequest request, HttpServletResponse response) {
    25. 		System.out.println("在同一个servlet中调用edit方法");
    26. 		
    27. 	}
    28.  
    29. 	private void del(HttpServletRequest request, HttpServletResponse response) {
    30. 		System.out.println("在同一个servlet中调用del方法");
    31. 		
    32. 	}
    33.  
    34. 	private void add(HttpServletRequest request, HttpServletResponse response) {
    35. 		System.out.println("在同一个servlet中调用add方法");
    36. 		
    37. 	}
    38.  
    39. 	
    40. }

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  • 原文地址：https://blog.csdn.net/weixin_67338832/article/details/125455189