java/src/main/com/google/appengine/tools/development/HeaderVerificationFilter.java

   1 // Copyright 2011 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.tools.development;
   4
   5 import java.io.IOException;
   6
   7 import javax.servlet.Filter;
   8 import javax.servlet.FilterChain;
   9 import javax.servlet.FilterConfig;
  10 import javax.servlet.ServletException;
  11 import javax.servlet.ServletRequest;
  12 import javax.servlet.ServletResponse;
  13 import javax.servlet.http.HttpServletRequest;
  14 import javax.servlet.http.HttpServletResponse;
  15
  16 /**
  17  * A Filter that verifies that the incoming request's headers are valid.
  18  *
  19  */
  20 public class HeaderVerificationFilter implements Filter {
  21   private static final String CONTENT_LENGTH = "Content-Length";
  22
  23   @Override
  24   public void init(FilterConfig filterConfig) {}
  25
  26   @Override
  27   public void destroy() {}
  28
  29   @Override
  30   public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
  31       throws IOException, ServletException {
  32     if (doFilterInternal(request, response)) {
  33       chain.doFilter(request, response);
  34     }
  35   }
  36
  37   /**
  38    * Helper method for doFilter() that contains the filtering logic but does
  39    * not invoke the remaining filters in the chain.
  40    *
  41    * @return true if the request should be passed to the remaining filters in the chain.
  42    */
  43   private boolean doFilterInternal(ServletRequest request, ServletResponse response)
  44       throws IOException {
  45     if (!(request instanceof HttpServletRequest)) {
  46       return true;
  47     }
  48     if (!(response instanceof HttpServletResponse)) {
  49       return true;
  50     }
  51     HttpServletRequest httpRequest = (HttpServletRequest) request;
  52     HttpServletResponse httpResponse = (HttpServletResponse) response;
  53
  54     if (httpRequest.getMethod().equals("POST") &&
  55         httpRequest.getHeader(CONTENT_LENGTH) == null) {
  56       httpResponse.sendError(HttpServletResponse.SC_LENGTH_REQUIRED, "Length required");
  57       return false;
  58     }
  59
  60     return true;
  61   }
  62 }