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[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;

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