web.xml内容如下:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>firstWeb</display-name>
  <servlet>
   <servlet-name>abcd2</servlet-name>
   <servlet-class>aa.PopulateBeanServlet</servlet-class>
  </servlet>
  <servlet-mapping>
   <servlet-name>abcd2</servlet-name>
   <url-pattern>/*</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>/firstWeb/abc</welcome-file>
  </welcome-file-list>
</web-app>运行后,浏览器显示404错误,哪里配置错了吗?