• 自定义MVC原理

    目录

    一、什么是MVC？

    二、初版的增删改查

    三、类过多的优化

     四、反射优化

    五、MVC工作原理以及对应打码

    一、什么是MVC？

    M:model
    V:view
    C:controller
    分工明确，各司其职
    降低代码耦合度

    二、初版的增删改查

    写一个Demo01.jsp

    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>Insert title here</title>
    8. </head>
    9. <body>
    10. 	<h3>目前增删改查的方法</h3>
    11. <a href="${pageContext.request.contextPath }/book/add">增加</a>
    12. <a href="${pageContext.request.contextPath }/book/del">删除</a>
    13. <a href="${pageContext.request.contextPath }/book/edit">修改</a>
    14. <a href="${pageContext.request.contextPath }/book/list">查询</a>
    15. <!-- 
    16. 	上述问题：
    17. 		1.关于单个实体/表操作场景越多，需要新建的类越多，造成了项目中类的数量过于庞大
    18. 		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代码
    19.  		3.反射相关代码，在每一个实体类对应的servlet中都存在
    20.  		4.每一个servlet中都有doget、dopost方法
    21.  -->
    22. </body>
    23. </html>

    再写四个servlet在com.cdl.web包下

    AddBookServlet

    1. package com.cdl.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. /**
    11.  * Servlet implementation class AddBookServlet
    12.  */
    13. @WebServlet("/book/add")
    14. public class AddBookServlet extends HttpServlet {
    15. 	
    16. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    17. 		doPost(request, response);
    18. 	}
    19.  
    20. 	/**
    21. 	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
    22. 	 */
    23. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    24. 		System.out.println("处理书籍的增加业务，调用BookBiz");
    25. 	}
    26.  
    27. }

    DelBookServlet

    1. package com.cdl.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.  
    11. @WebServlet("/book/del")
    12. public class DelBookServlet extends HttpServlet {
    13. 	
    14. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    15. 		doPost(request, response);
    16. 	}
    17.  
    18. 	
    19. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    20. 		System.out.println("处理书籍的删除业务，调用BookBiz");
    21. 	}
    22.  
    23. }

    EditBookServlet

    1. package com.cdl.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. /**
    11.  * Servlet implementation class EditBookServlet
    12.  */
    13. @WebServlet("/book/edit")
    14. public class EditBookServlet extends HttpServlet {
    15. 	
    16. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    17. 		doPost(request, response);
    18. 	}
    19.  
    20. 	
    21. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    22. 		System.out.println("处理书籍的编辑业务，调用BookBiz");
    23. 	}
    24.  
    25. }

    ListBookServlet

    1. package com.cdl.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. /**
    11.  * Servlet implementation class EditBookServlet
    12.  */
    13. @WebServlet("/book/list")
    14. public class ListBookServlet extends HttpServlet {
    15. 	
    16. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    17. 		doPost(request, response);
    18. 	}
    19.  
    20. 	
    21. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    22. 		System.out.println("处理书籍的查询业务，调用BookBiz");
    23. 	}
    24.  
    25. }

    当点击增加控制台输出

    点其他时

     

    三、类过多的优化

    建一个BookServlet

    1. package com.cdl.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. @WebServlet("/book.action")
    14. public class BookServlet extends HttpServlet {
    15. 	
    16. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    17. 		doPost(request, response);
    18. 	}
    19.  
    20. 	
    21. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    22. //		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
    23. 		String methodName = request.getParameter("methodName");
    24.  
    25. 		
    26. 		if("add".equals(methodName)){
    27. 			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
    28. 			add(req,resp);
    29. 		}
    30. 		else if("del".equals(methodName)) {
    31. 			del(req,resp);
    32. 		}
    33. 		else if("edit".equals(methodName)) {
    34. 			edit(req,resp);
    35. 		}
    36. 		else if("list".equals(methodName)) {
    37. 			list(req,resp);
    38. 		}
    39. 		else if("load".equals(methodName)) {
    40. 			load(req,resp);
    41. 		}
    42. 	}
    43.  
    44. 	private void list(HttpServletRequest req, HttpServletResponse resp) {
    45. 		System.out.println("在用一个servlet中调用 list 方法");
    46. 	}
    47. 	
    48. 	private void load(HttpServletRequest req, HttpServletResponse resp) {
    49. 		System.out.println("在用一个servlet中调用 list 方法");
    50. 	}
    51. 	
    52. 	private void edit(HttpServletRequest req, HttpServletResponse resp) {
    53. 		System.out.println("在用一个servlet中调用 edit 方法");
    54. 	}
    55.  
    56. 	private void del(HttpServletRequest req, HttpServletResponse resp) {
    57. 		System.out.println("在用一个servlet中调用 del 方法");
    58. 	}
    59.  
    60. 	private void add(HttpServletRequest req, HttpServletResponse resp) {
    61. 		System.out.println("在用一个servlet中调用 add 方法");
    62. 	}
    63. 		
    64. 	
    65. 	}
    66.  
    67.

     Demo01.jsp

    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>Insert title here</title>
    8. </head>
    9. <body>
    10. 	<h3>目前增删改查的方法</h3>
    11. <a href="${pageContext.request.contextPath }/book/add">增加</a>
    12. <a href="${pageContext.request.contextPath }/book/del">删除</a>
    13. <a href="${pageContext.request.contextPath }/book/edit">修改</a>
    14. <a href="${pageContext.request.contextPath }/book/list">查询</a>
    15. <!-- 
    16. 	上述问题：
    17. 		1.关于单个实体/表操作场景越多，需要新建的类越多，造成了项目中类的数量过于庞大
    18. 		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代码
    19.  		3.反射相关代码，在每一个实体类对应的servlet中都存在
    20.  		4.每一个servlet中都有doget、dopost方法
    21.  -->
    22. <h3>类数量过多问题的优化</h3>
    23. <a href="${pageContext.request.contextPath }/book.action?methodName=add">增加</a>
    24. <a href="${pageContext.request.contextPath }/book.action?methodName=del">删除</a>
    25. <a href="${pageContext.request.contextPath }/book.action?methodName=edit">修改</a>
    26. <a href="${pageContext.request.contextPath }/book.action?methodName=list">查询</a>
    27. <a href="${pageContext.request.contextPath }/book.action?methodName=load">回显</a>
    28.  
    29. </body>
    30. </html>

    结果

    点击修改和删除 控制台：

     

     四、反射优化

    改变三中的BookServlet

    1. package com.cdl.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. @WebServlet("/book.action")
    14. public class BookServlet extends HttpServlet {
    15. 	
    16. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    17. 		doPost(request, response);
    18. 	}
    19.  
    20. 	
    21. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    22. //		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
    23. 		String methodName = request.getParameter("methodName");
    24. //		methodName可能是add/del/edit/list/load/xxx/yyy/aaa...
    25. //		前台传递什么方法，就调用当前类的对应方法
    26. 		try {
    27. 			 Method m = this.getClass().getDeclaredMethod(methodName, HttpServletRequest.class,HttpServletResponse.class);
    28. 			m.setAccessible(true);
    29. //			调用当前类实例的methodName方法
    30. 			m.invoke(this, request,response);
    31. 		} catch (Exception e) {
    32. 			// TODO Auto-generated catch block
    33. 			e.printStackTrace();
    34. 		} 
    35. 		
    36. 		
    37. 		
    38. //		if("add".equals(methodName)){
    39. //			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
    40. //			add(req,resp);
    41. //		}
    42. //		else if("del".equals(methodName)) {
    43. //			del(req,resp);
    44. //		}
    45. //		else if("edit".equals(methodName)) {
    46. //			edit(req,resp);
    47. //		}
    48. //		else if("list".equals(methodName)) {
    49. //			list(req,resp);
    50. //		}
    51. //		else if("load".equals(methodName)) {
    52. //			load(req,resp);
    53. //		}
    54. 	}
    55.  
    56. 	private void list(HttpServletRequest req, HttpServletResponse resp) {
    57. 		System.out.println("在用一个servlet中调用 list 方法");
    58. 	}
    59. 	
    60. 	private void load(HttpServletRequest req, HttpServletResponse resp) {
    61. 		System.out.println("在用一个servlet中调用 list 方法");
    62. 	}
    63. 	
    64. 	private void edit(HttpServletRequest req, HttpServletResponse resp) {
    65. 		System.out.println("在用一个servlet中调用 edit 方法");
    66. 	}
    67.  
    68. 	private void del(HttpServletRequest req, HttpServletResponse resp) {
    69. 		System.out.println("在用一个servlet中调用 del 方法");
    70. 	}
    71.  
    72. 	private void add(HttpServletRequest req, HttpServletResponse resp) {
    73. 		System.out.println("在用一个servlet中调用 add 方法");
    74. 	}
    75. 		
    76. 	
    77. 	}
    78.  
    79.

    和三一致效果

    五、MVC工作原理以及对应打码

     

    在com.cdl.web中建一个OrderServlet

    1. package com.cdl.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. @WebServlet("/order.action")
    14. public class OrderServlet extends HttpServlet {
    15. 	
    16. 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    17. 		doPost(request, response);
    18. 	}
    19.  
    20. 	
    21. 	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    22. //		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
    23. 		String methodName = request.getParameter("methodName");
    24. //		methodName可能是add/del/edit/list/load/xxx/yyy/aaa...
    25. //		前台传递什么方法，就调用当前类的对应方法
    26. 		try {
    27. 			Method m = this.getClass().getDeclaredMethod(methodName, HttpServletRequest.class,HttpServletResponse.class);
    28. 			m.setAccessible(true);
    29. //			调用当前类实例的methodName方法
    30. 			m.invoke(this, request,response);
    31. 		} catch (Exception e) {
    32. 			// TODO Auto-generated catch block
    33. 			e.printStackTrace();
    34. 		} 
    35. 		
    36. 		
    37. 		
    38. //		if("add".equals(methodName)){
    39. //			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
    40. //			add(req,resp);
    41. //		}
    42. //		else if("del".equals(methodName)) {
    43. //			del(req,resp);
    44. //		}
    45. //		else if("edit".equals(methodName)) {
    46. //			edit(req,resp);
    47. //		}
    48. //		else if("list".equals(methodName)) {
    49. //			list(req,resp);
    50. //		}
    51. //		else if("load".equals(methodName)) {
    52. //			load(req,resp);
    53. //		}
    54. 	}
    55.  
    56. 	private void list(HttpServletRequest req, HttpServletResponse resp) {
    57. 		System.out.println("在用一个order中调用 list 方法");
    58. 	}
    59. 	
    60. 	private void load(HttpServletRequest req, HttpServletResponse resp) {
    61. 		System.out.println("在用一个order中调用 list 方法");
    62. 	}
    63. 	
    64. 	private void edit(HttpServletRequest req, HttpServletResponse resp) {
    65. 		System.out.println("在用一个order中调用 edit 方法");
    66. 	}
    67.  
    68. 	private void del(HttpServletRequest req, HttpServletResponse resp) {
    69. 		System.out.println("在用一个order中调用 del 方法");
    70. 	}
    71.  
    72. 	private void add(HttpServletRequest req, HttpServletResponse resp) {
    73. 		System.out.println("在用一个order中调用 add 方法");
    74. 	}
    75. 	
    76.  
    77. }

    Demo02.jsp

    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>Insert title here</title>
    8. </head>
    9. <body>
    10. 	<h3>目前增删改查的方法</h3>
    11. <a href="${pageContext.request.contextPath }/book/add">增加</a>
    12. <a href="${pageContext.request.contextPath }/book/del">删除</a>
    13. <a href="${pageContext.request.contextPath }/book/edit">修改</a>
    14. <a href="${pageContext.request.contextPath }/book/list">查询</a>
    15. <!-- 
    16. 	上述问题：
    17. 		1.关于单个实体/表操作场景越多，需要新建的类越多，造成了项目中类的数量过于庞大
    18. 		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代码
    19.  		3.反射相关代码，在每一个实体类对应的servlet中都存在
    20.  		4.每一个servlet中都有doget、dopost方法
    21.  -->
    22. <h3>类数量过多问题的优化</h3>
    23. <a href="${pageContext.request.contextPath }/book.action?methodName=add">增加</a>
    24. <a href="${pageContext.request.contextPath }/book.action?methodName=del">删除</a>
    25. <a href="${pageContext.request.contextPath }/book.action?methodName=edit">修改</a>
    26. <a href="${pageContext.request.contextPath }/book.action?methodName=list">查询</a>
    27. <a href="${pageContext.request.contextPath }/book.action?methodName=load">回显</a>
    28.  
    29. <h3>订单类CRUD</h3>
    30. <a href="${pageContext.request.contextPath }/order.action?methodName=add">增加</a>
    31. <a href="${pageContext.request.contextPath }/order.action?methodName=del">删除</a>
    32. <a href="${pageContext.request.contextPath }/order.action?methodName=edit">修改</a>
    33. <a href="${pageContext.request.contextPath }/order.action?methodName=list">查询</a>
    34. <a href="${pageContext.request.contextPath }/order.action?methodName=load">回显</a>
    35. </body>
    36. </html>


    运行代码：

     建一个com.cdl.framework的包

    建一个DispatcherServlet

    1. package com.cdl.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.http.HttpServlet;
    9. import javax.servlet.http.HttpServletRequest;
    10. import javax.servlet.http.HttpServletResponse;
    11.  
    12. import com.cdl.web.BookAction;
    13.  
    14. /**
    15.  * 中央控制器
    16.  * 主要职能：接收浏览器请求，找到对应的处理人
    17.  * @author 陈冬丽
    18.  *
    19.  */
    20. public class DispatcherServlet extends HttpServlet{
    21. 	private Map<String, Action> actions = new HashMap<String, Action>();
    22. //	程序启动时，只会加载一次
    23. 	
    24. 	@Override
    25. 	public void init() throws ServletException {
    26. 		actions.put("/book", new BookAction());
    27. //		actions.put("/order", new BooKAction());
    28. 	}
    29. 	
    30. 	@Override
    31. 	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    32. 		doPost(req, resp);
    33. 	}
    34. 	
    35. 	@Override
    36. 	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    37. 		//http://localhost:8080/mvc/book.aciton?methodName=list
    38. 		String uri = req.getRequestURI();
    39. 		//要拿到/book，就是最后一个/到最后一个点的位置
    40. 		uri=uri.substring(uri.lastIndexOf("/"), uri.lastIndexOf("."));
    41. 		Action action = actions.get(uri);
    42. 		action.execute(req, resp);
    43. 	}
    44. 	
    45. }

    ActionSupport

    1. package com.cdl.framework;
    2.  
    3. import java.lang.reflect.Method;
    4.  
    5. import javax.servlet.http.HttpServletRequest;
    6. import javax.servlet.http.HttpServletResponse;
    7.  
    8. public class ActionSupport implements Action {
    9.  
    10. 	@Override
    11. 	public void execute(HttpServletRequest req, HttpServletResponse resp) {
    12. 		String methodName = req.getParameter("methodName");
    13. //		methodName可能是add/del/edit/list/load/xxx/yyy/aaa...
    14. //		前台传递什么方法，就调用当前类的对应方法
    15. 		try {
    16. 			Method m = this.getClass().getDeclaredMethod(methodName,  HttpServletRequest.class,HttpServletResponse.class);
    17. 			//打开访问权限
    18. 			m.setAccessible(true);
    19. //			调用当前类实例的methodName方法
    20. 			m.invoke(this, req,resp);
    21. 		} catch (Exception e) {
    22. 			// TODO: handle exception
    23. 			e.printStackTrace();
    24. 		}
    25. 	}
    26. 	
    27. 	private void list(HttpServletRequest req, HttpServletResponse resp) {
    28. 		System.out.println("在用一个servlet中调用list方法");
    29. 	}
    30. 	
    31. 	private void load(HttpServletRequest req, HttpServletResponse resp) {
    32. 		System.out.println("在用一个servlet中调用list方法");
    33. 	}
    34. 	
    35. 	private void edit(HttpServletRequest req, HttpServletResponse resp) {
    36. 		System.out.println("在用一个servlet中调用edit方法");
    37. 	}
    38. 	
    39. 	private void del(HttpServletRequest req, HttpServletResponse resp) {
    40. 		System.out.println("在用一个servlet中调用del方法");
    41. 	}
    42. 	
    43. 	private void add(HttpServletRequest req, HttpServletResponse resp) {
    44. 		System.out.println("在用一个servlet中调用add方法");
    45. 	}
    46. 	
    47.  
    48. }

    Action

    1. package com.cdl.framework;
    2.  
    3. import javax.servlet.http.HttpServletRequest;
    4. import javax.servlet.http.HttpServletResponse;
    5.  
    6. /**
    7.  * 子控制器
    8.  * 对应请求的处理人
    9.  * @author 陈冬丽
    10.  *
    11.  */
    12. public interface Action {
    13. 	void execute(HttpServletRequest req,HttpServletResponse resp);
    14. }

  • 相关阅读:
    RabbitMQ之消息应答和持久化
    k8s-2 集群升级
    ECharts数据可视化项目
    小程序与uniapp如何进行传参
    计算机网络第五章问答题
    B树、B+树、红黑树的定义、之间的区别、优缺点、数据结构、应用等
    软件工程-第7章 面向对象方法基础
    造一个CPU
    （C语言）背答案
    人大与加拿大女王大学金融硕士——带你了解GMAT考试为何如此重要
  • 原文地址：https://blog.csdn.net/weixin_62735525/article/details/125455529