servlet获取web.xml中的信息

web.xml中的文件配置如下：

<servlet>

   <servlet-name>a</servlet-name>
   <servlet-class>com.qq1009108034.zxg.AServlet</servlet-class>
   <!-- 初始化参数被封装在servlet中 -->
   <init-param>
      <param-name>driver</param-name>
      <param-value>com.mysql.jdbc.Driver</param-value>
   </init-param>
   <init-param>
      <param-name>url</param-name>
      <param-value>jdbc:mysql://localhost:3306/shop</param-value>
   </init-param>
   <init-param>
      <param-name>user</param-name>
      <param-value>root</param-value>
   </init-param>
   <init-param>
      <param-name>password</param-name>
      <param-value>123</param-value>
   </init-param>
</servlet>
<servlet-mapping>
   <servlet-name>a</servlet-name>
   <url-pattern>/a</url-pattern>

</servlet-mapping>

 JAVA代码如下：

public class AServlet implements Servlet {
    private ServletConfig config;
    public void init(ServletConfig config) throws ServletException {
//       System.out.println("servletConfig="+arg0.toString());
this.config=config;
}
public void service(ServletRequest arg0, ServletResponse response)
throws ServletException, IOException {

               //获取servletConfig
 ServletConfig config=getServletConfig();
//通过初始化的name获取value
 String driver=config.getInitParameter("driver");
 String url=config.getInitParameter("url");
 String user=config.getInitParameter("user");
 String password=config.getInitParameter("password");
 response.setContentType("text/html;charset=UTF-8");
 PrintWriter out=response.getWriter();
out.print(driver);
out.print(url);
out.print(user);
out.print(password);


}