【C014043】阅读 代码如下,哪种方式可以正确的获取到encoding的值（ ）。

web.xml

 <filter>

  <filter-name>EnCodingFilter</filter-name>

  <filter-class>org.jbit.bdqn.web.filter.EnCodingFilter</filter-class>

  <init-param>

   <param-name>encoding</param-name>

   <param-value>utf-8</param-value>

  </init-param>

 </filter>

 <filter-mapping>

  <filter-name>EnCodingFilter</filter-name>

  <url-pattern>/*</url-pattern>

 </filter-mapping>

• A.public class EnCodingFilter implements Filter {
  
   public void init(FilterConfig filterConfig) throws ServletException {
  
    String  enCoding = filterConfig.getInitParameter("encoding");
  
   }
  
  }

• B.public class EnCodingFilter extends HttpServlet {
  
   public void init(ServletConfig config) throws ServletException {
  
    super.init(config);
  
    String encoding=config.getInitParameter("encoding");
  
   }
  
  }

• C.public class EnCodingFilter implements Filter {
  
   public void doFilter(ServletRequest request, ServletResponse response,
  
     FilterChain finChain) throws IOException, ServletException {
  
    String encoding=request.getParameter("encoding");
  
   }
  
  }

• D.public class EnCodingFilter extends HttpServlet {
  
   public void doPost(HttpServletRequest request, HttpServletResponse response)
  
     throws ServletException, IOException {
  
    String currPage=request.getParameter("encoding ");
  
   }
  
  }