Java Servlet

package cn.nanchengyu.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
/**
 * ClassName: UserServlet
 * Package: cn.nanchengyu.servlet
 * Description:
 *
 * servlet开发流程
 * 1.创建Javaweb项目，同时将tomcat添加为当前项目的依赖
 * 2.重写service方法，service（HttpServletRequest req, HttpServletResponse resp）
 * 3.在service方法中，定义业务处理代码
 * 4.在web.xml中配置Servlet对应的请求映射路径
 * @Author 南城余
 * @Create 2023/11/20 11:26
 * @Version 1.0
 */
public class UserServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        1.从request对象中获取请求中的任何信息（username参数）
        String username = request.getParameter("username");
//        2.处理业务代码
        String info = "yes";
        if("nanchengyu".equals(username)){
            info = "no";
        }
//        3.将响应的数据放入response中
        // 应该设置Content-Type响应头
        response.setHeader("Content-Type","text/html");
        PrintWriter writer = response.getWriter();
        writer.write(info);
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee https://jakarta.ee/xml/ns/jakartaee/web-app_5_0.xsd"
         version="5.0">
    <servlet>
        <!--给UserServlet起一个别名-->
        <servlet-name>userServlet</servlet-name>
        <servlet-class>com.atguigu.servlet.UserServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <!--关联别名和映射路径-->
        <servlet-name>userServlet</servlet-name>
        <!--可以为一个Servlet匹配多个不同的映射路径,但是不同的Servlet不能使用相同的url-pattern-->
        <url-pattern>/userServlet</url-pattern>
       <!-- <url-pattern>/userServlet2</url-pattern>-->
        <!--
            /        表示通配所有资源,不包括jsp文件
            /*       表示通配所有资源,包括jsp文件
            /a/*     匹配所有以a前缀的映射路径
            *.action 匹配所有以action为后缀的映射路径
        -->
       <!-- <url-pattern>/*</url-pattern>-->
    </servlet-mapping>
</web-app>

@WebServlet(
        name = "userServlet",
        //value = "/user",
        urlPatterns = {"/userServlet1","/userServlet2","/userServlet"},
        initParams = {@WebInitParam(name = "encoding",value = "UTF-8")},
        loadOnStartup = 6
)
public class UserServlet  extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String encoding = getServletConfig().getInitParameter("encoding");
        System.out.println(encoding);
        // 获取请求中的参数
        String username = req.getParameter("username");
        if("atguigu".equals(username)){
            //通过响应对象响应信息
            resp.getWriter().write("NO");
        }else{
            resp.getWriter().write("YES");
        }
    }
}