1. 原有的Servlet

package com.mytest.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @author Sommer1111
 * @date 2021/3/16 8:45
 */
public class HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//        接受了请求，取得参数，将数据存进去
        String method = req.getParameter("method");
        if(method.equals("add")){
            req.getSession().setAttribute("msg","调用了add方法");
        }else if(method.equals("delete")){
            req.getSession().setAttribute("msg","调用了delete方法");
        }
//页面重定向，跳转到该hello页面
        req.getRequestDispatcher("/WEB-INF/jsp/hello.jsp").forward(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

2. 新增一个一样的Servlet

package com.mytest.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @author sommer1111
 * @date 2021/4/13 19:12
 */
public class Test extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String method = req.getParameter("method");
        if(method.equals("add")){
            req.getSession().setAttribute("msg","调用了add方法");
        }else{
            req.getSession().setAttribute("msg","调用了delete方法");
        }
        req.getRequestDispatcher("/WEB-INF/jsp/hello.jsp").forward(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req,resp);
    }
}

3.在web.xml中注册servlet

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    
    <servlet>
        <servlet-name>HelloServlet</servlet-name>
        <servlet-class>com.mytest.servlet.HelloServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>HelloServlet</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>Test</servlet-name>
        <servlet-class>com.mytest.servlet.Test</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Test</servlet-name>
        <url-pattern>/test</url-pattern>
    </servlet-mapping>
</web-app>

4. 访问

http://localhost:8080/SpringMVC_01_Servlet_war_exploded/hello?method

但是访问

http://localhost:8080/SpringMVC_01_Servlet_war_exploded/test?method

报错找不到资源

5.原因分析

.out 文件的web.xml中没有生成Test的servlet注册信息，所以找不到资源

原因分析：暂时不知，先留着