[原创]java WEB学习笔记22：MVC案例完整实践(part 3)---多个请求对应一个Servlet解析

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多个请求对应一个Servlet解析

如果我们每一个请求对应一个Servelt，这样的话，代码就显得比较臃肿，最主要的是，也不方便系代码的管理和优化

方式一：

　　

　

　　1. 思路：对于每一个页面请求我们设置成一个对应的方法，并且为请求的url设置相应的method参数，servlet-mapping 为  @WebServlet("/customerServlet")  ,而在Servlet 中通过获取 method 参数不同的取值，通过一个switch 语句选择不同的方法，同时调用不同的方法。

　　

　　2. 代码：test1.jsp ,  CustomerServlet1.java

　　test.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>测试</title>
 </head>
 <body>

             <a href="customerServlet?method=add">Add1</a>
             <br><br>

             <a href="customerServlet?method=query">Query1</a>
             <br><br>

             <a href="customerServlet?method=delete">Delete1</a>
             <br><br>
             <br><br>
             <br><br>

 </body>
 </html>

　　CustomerServlet1.java

 package com.jason.mvcapp.servlet;

 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;

 /**
  * Servlet implementation class CustomerServlet
  */
 @WebServlet("/customerServlet")
 public class CustomerServlet1 extends HttpServlet {
     private static final long serialVersionUID = 1L;

     /**
      *
      */
     protected void doGet(HttpServletRequest request,
             HttpServletResponse response) throws ServletException, IOException {
         doPost(request, response);
     }

     protected void doPost(HttpServletRequest request,
             HttpServletResponse response) throws ServletException, IOException {

         String method = request.getParameter("method");

         switch (method) {
         case "add":
             add(request, response);
             break;
         case "query":
             query(request, response);
             break;
         case "delete":
             delete(request, response);
             break;
         }

     }

     private void delete(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         System.out.println("delete");

     }

     private void query(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         System.out.println("query");

     }

     private void add(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         System.out.println("add");
     }

 }

方法二：

　　1. 思路：将所有的请求都设置成 方法名.do, 而将 servlet-mapping 为 @WebServlet("*.do")，即响应所有以 .do 结尾的请求.在Servlet中通过反射，获取运行时类，之后invoke() 调用方法

　　2.代码：test2.jsp ,  CustomerServlet2.java

　　test2.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>测试2</title>
 </head>
 <body>

             <a href="addCustomer.do">Add2</a>
             <br><br>

             <a href="query.do">Query2</a>
             <br><br>

             <a href="deleteCustomer.do">Delete2</a>
             <br><br>

             <a href="update.do">Update2</a>
             <br><br>

             <a href="editeCustomer.do">Edite2</a>
             <br><br>

 </body>
 </html>

　　CustomerServlet2.java

 package com.jason.mvcapp.servlet;

 import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 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;

 /**
  * Servlet implementation class CustomerServlet2
  */
 @WebServlet("*.do")
 public class CustomerServlet2 extends HttpServlet {
     private static final long serialVersionUID = 1L;

     protected void doGet(HttpServletRequest request,
             HttpServletResponse response) throws ServletException, IOException {
         doPost(request, response);
     }

     protected void doPost(HttpServletRequest request,
             HttpServletResponse response) throws ServletException, IOException {
         //1.获取servletPath：/add.do 或者 query.do
28         String serveltPath = request.getServletPath();
29
30          System.out.println(serveltPath);
31         //2.去除/ 和 .do 得到对应的方法，如 add  query
32         String methodName = serveltPath.substring(1);
33         methodName = methodName.substring(0, methodName.length() - 3);
34         // System.out.println(methodName);
35
36         try {
37             //3.利用反射获取methodName对应的方法
38             Method method = getClass().getDeclaredMethod(methodName,
39                     HttpServletRequest.class, HttpServletResponse.class);
40
41             //4.利用反射调用方法
42             method.invoke(this, request, response);
43         } catch (Exception e) {
44
45             e.printStackTrace();
46         }
     }

     private void update(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         System.out.println("update");

     }

     private void editeCustomer(HttpServletRequest request,
             HttpServletResponse response) throws ServletException, IOException {
         System.out.println("edit");

     }

     private void deleteCustomer(HttpServletRequest request,
             HttpServletResponse response) throws ServletException, IOException {
         System.out.println("delete");

     }

     private void query(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         System.out.println("query");

     }

     private void addCustomer(HttpServletRequest request,
             HttpServletResponse response) throws ServletException, IOException {
         System.out.println("add");
     }

 }

总结：

　　1）理解由方式一过度到方法二;

　　2）理解反射获取当前类，获取提交的方法，及解析，调用相应的方法;