Problems with servlet in web.xml configuration

The basic configuration is as follows

<!-- 配置servlet -->
    <servlet>
    	<!-- 配置Servlet的名称 -->
    	<servlet-name>HelloServlet</servlet-name>
    	<!-- 配置Servlet全路径 -->
    	<servlet-class>servlet.HelloServlet</servlet-class>
    </servlet>
    
    <!-- 配置servlet映射 -->
    <servlet-mapping>
    	<!-- 配置servlet名称，与上面那个要一样 -->
    	<servlet-name>HelloServlet</servlet-name>
    	<!-- 配置访问路径，即地址栏最后的路径 -->
    	<url-pattern>/hello</url-pattern>
    </servlet-mapping>

However, after entering the following content in the address bar, it keeps displaying 404, the resource is not found.

Later, it was discovered that it was written <welcome-file-list>into the tag pair, which also caused <servlet>the tag pair to be red. Just write it outside.