1.新建项目

菜单->File->New->Project->勾上 Web Application(3.1)->OK

2.项目目录

3.新建目录

右键WEB-INF->New->Directory 新建两个目录：
classes和lib目录

4.新建HelloServlet

选中src目录，然后右键鼠标->New->Servlet->输入HelloServlet

import java.io.IOException;
import java.util.Date;
 
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
public class HelloServlet extends HttpServlet{
 
    public void doGet(HttpServletRequest request, HttpServletResponse response){
         
        try {
            response.getWriter().println("<h1>Hello Servlet!</h1>");
            response.getWriter().println(new Date().toLocaleString());
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
     
}

5.导入jar包

点击 project structure
点击 Libraries
点击加号，选中Java
指定E:\project\j2ee\web\WEB-INF\lib\servlet-api.jar
点击ok
这个行为做过之后服务端HelloServlet的编译错误就消失了

6.指定输出目录

打开project structure
设置 project complier output 为：

E:\project\j2ee\web\WEB-INF\classes

7.修改web.xml

在web.xml中添加/hello路径的映射

<?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_3_1.xsd"
         version="3.1">
    <servlet>
        <servlet-name>HelloServlet</servlet-name>
        <servlet-class>HelloServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>HelloServlet</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>
</web-app>