content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.web;
  
  import java.io.IOException;
  import javax.servlet.Filter;
  import javax.servlet.FilterChain;
  import javax.servlet.FilterConfig;
  import javax.servlet.ServletException;
  import javax.servlet.ServletRequest;
  import javax.servlet.ServletResponse;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  /**
   * Provides an abstract class to be subclassed to create an HTTP filter.
   */
  public abstract class HttpFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
  
    @Override
    public void destroy() {
    }
  
    @Override
    public final void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
        throws IOException, ServletException {
      if (!(req instanceof HttpServletRequest && resp instanceof HttpServletResponse)) {
        throw new ServletException(
            String.format("Received non-HTTP request or response: req=%s, resp=%s",
                req.getClass(), resp.getClass()));
      }
  
      HttpServletRequest request = (HttpServletRequest) req;
      HttpServletResponse response = (HttpServletResponse) resp;
  
      doFilter(request, response, chain);
    }
  
    /**
     * Receives standard HTTP requests from the public doFilter method.
     * @param req http request
     * @param resp http response
     * @param chain filter chain
     */
    public abstract void doFilter(HttpServletRequest req, HttpServletResponse resp, FilterChain chain)
        throws IOException, ServletException;
  }
  