Servlet系列两种创建方式

<?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" id="WebApp_ID" version="4.0">
  <display-name>java-servlet-demo02</display-name>
  <!-- servlet配置 -->
  <servlet>
    <!-- 名称 -->
    <servlet-name>WebXmlServlet</servlet-name>
    <!-- servlet全称类名 -->
    <servlet-class>com.mcode.servlet.controller.WebXmlServlet</servlet-class>
    <!-- 启动的优先级，数字越小越先起作用 -->
    <load-on-startup>1</load-on-startup>
  </servlet>
  <!-- 映射配置 -->
  <servlet-mapping>
    <!-- 对应名称 -->
    <servlet-name>WebXmlServlet</servlet-name>
    <!-- 资源匹配规则：精确匹配 -->
    <url-pattern>/webxml</url-pattern>
  </servlet-mapping>
</web-app>

package com.mcode.servlet.controller;

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

/**
 * ClassName: WebXmlServlet
 * Package: com.mcode.servlet.controller
 * Description:
 *
 * @Author robin
 * @Version 1.0
 */
public class WebXmlServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置编码方式
        resp.setCharacterEncoding("UTF-8");
        //指定客户端解码方式
        resp.setHeader("content-type", "text/html;charset=UTF-8");
        //输出
        resp.getWriter().write("基于webxml方式配置的servlet");
    }
}

package com.mcode.servlet.controller;

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

/**
 * ClassName: AnnotationServlet
 * Package: com.mcode.servlet.controller
 * Description:
 *
 * @Author robin
 * @Version 1.0
 */
@WebServlet("/annotation")
public class AnnotationServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置编码方式
        response.setCharacterEncoding("UTF-8");
        //指定客户端解码方式
        response.setHeader("content-type", "text/html;charset=UTF-8");
        //输出
        response.getWriter().write("基于注解方式配置的servlet");
    }
}

package com.mcode;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.Method;

/**
 * ClassName: BaseServlet
 * Package: com.mcode
 * Description:
 *
 * @Author: robin
 * @Version: v1.0
 */
public abstract class BaseServlet extends HttpServlet {
    @Override
    public void service(HttpServletRequest request, HttpServletResponse response) {
        try {
          
            request.setCharacterEncoding("UTF-8");
          
            response.setCharacterEncoding("UTF-8");
          
            response.setContentType("text/html;charset=utf-8");
          
            String methodName = request.getParameter("method");
          
            if (methodName == null || methodName.trim().isEmpty()) {
                throw new RuntimeException("您没有传递 method 参数! 无法确定您想调用的方法");
            }
          
            Class<? extends BaseServlet> classz = this.getClass();
          
            Method method = classz.getMethod(methodName, HttpServletRequest.class,
                    HttpServletResponse.class);
          
            method.setAccessible(true);//开启暴力反射

            method.invoke(this, request, response);
          
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

package com.mcode;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

/**
 * ClassName: UserServlet
 * Package: com.mcode
 * Description:
 *
 * @Author: robin
 * @Version: v1.0
 */
@WebServlet("/user")
public class UserServlet extends BaseServlet{
    public void getList(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String method = request.getParameter("method");
        HttpSession session = request.getSession();
        session.setAttribute("method",method);
        request.getRequestDispatcher("index.jsp").forward(request, response);
    }
}

    <dependency>
      <groupId>jakarta.servlet.jsp</groupId>
      <artifactId>jakarta.servlet.jsp-api</artifactId>
      <version>3.1.1</version>
    </dependency>

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<html>
<body>
  <a href="/user?method=getList" rel="external nofollow" >user</a>
  <%=session.getAttribute("method") %>
<%
   out.println(session.getAttribute("method"));
%>
</body>
</html>