Gareth Hunt

8 Responses to “Released: Modify Headers 0.6.3”

1. NettiCat Says:
   January 8th, 2008 at 7:59 am

   First reading about the “Modify Headers” extension I thought: That’s what I ‘m looking for.
   But after installing the extension, it revealed to modify outging (request-) headers only. No possibility to modify or remove server-sided response headers. Yes, I should have read your extension-description more carefully, you mentioned it.
   Ok, you may ask, why should I want to filter response headers? Answer: There are several reasons why you may want to filter server headers. One of them is to force caching in firefox.
   Many servers send anti-cache headers, preventing firefox to cache documents and/or pictures, so there will always be a (full) reload when pushing the back button. That’s really annoying. Anti-cache headers may be AGE, CACHE-CONTROL, EXPIRES, ETAG, PRAGMA, VARY and even more headers.
   I really would appreciate adding that feature.

2. gareth Says:
   January 8th, 2008 at 9:43 am

   Hi NettiCat. I had always thought that response headers are immutable, but I had a look at the documentation and it looks possible. I’ve added an enhancement request here: https://www.mozdev.org/bugs/show_bug.cgi?id=18455

   Feel free to add yourself as a CC on this.

   I have a lot of other features to add first, but I’ll add this to the roadmap for version 0.8 or 0.9.

3. NettiCat Says:
   January 18th, 2008 at 9:47 am

   Thank you! (for adding my request to the road map)

4. NettiCat Says:
   January 18th, 2008 at 10:14 am

   P.S.

   ACString getResponseHeader(in ACString header);

   void setResponseHeader(in ACString header, in ACString value, in boolean merge);

   http://developer.mozilla.org/en/docs/nsIHttpChannel

5. NettiCat Says:
   January 19th, 2008 at 3:30 pm

   This may not be of interest for bloggers, but as all postings will be reviewed I’ll post it anyway
   I made a small extension (BetterCache). It is a working demo concerning modification of response headers. You may use it in your own project:

   function RespHeaderObserver()
   {
   this.register();
   }

   RespHeaderObserver.prototype = {
   observe: function(subject, topic, data) {
   if (topic == “http-on-examine-response”) {
   var headers = new Array();
   headers[0] = “Age”;
   headers[1] = “Cache-Control”;
   headers[2] = “Date”;
   headers[3] = “ETag”;
   headers[4] = “Expires”;
   headers[5] = “Last-Modified”;
   headers[6] = “Pragma”;
   headers[7] = “Vary”;
   //headers[8] = “Set-Cookie”; //not anti-cache, but a better testpattern
   var httpChannel = subject.QueryInterface(Components.interfaces.nsIHttpChannel);
   //need to test every (above defined) header for existance. If not existant, getResponseHeader will throw an exception.
   for(i = 0; i < headers.length; i++){
   var headerval = “”;
   var replacement = “”;
   try{
   headerval = httpChannel.getResponseHeader (headers[i]);
   if(i == 6)//special case Pragma
   replacement = headerval.replace(/no\-cache/g, “”);
   httpChannel.setResponseHeader(headers[i], replacement, false);
   //alert(headers[i]+’='+headerval);
   }catch(e){}//NS_ERROR_(header_)NOT_AVAILABLE
   }
   headers = null;
   return;
   }
   },

   register: function() {
   var observerService = Components.classes["@mozilla.org/observer-service;1"].getService(Components.interfaces.nsIObserverService);
   observerService.addObserver(this, “http-on-examine-response”, false);
   },
   unregister: function() {
   var observerService = Components.classes["@mozilla.org/observer-service;1"].getService(Components.interfaces.nsIObserverService);
   try{
   observerService.removeObserver(this, “http-on-examine-response”);
   }catch(e){}
   }
   }
   //observer needs to be registered only once, so better use a XPT file
   window.addEventListener(”load”, function(evnt) { observer = new RespHeaderObserver(); }, true);
   window.addEventListener(”unload”, function(evnt) { observer.unregister(); }, true);

6. crono Says:
   January 21st, 2008 at 12:39 pm

   Hi,
   I found your extension today and think it’s really great. It would be perfect for me when I could specify which headers are sent to which url (with regex).

   Example:
   x-test0 = 0000 @ http://a-z\./]*
   x-test = 1234 @ https://localhost/*
   x-test2 = 5678 @ http://www\.mozilla\.org/*

   and so on… Just an idea

7. gareth Says:
   January 21st, 2008 at 1:03 pm

   Hi Crono, A feature similar to this is already on the roadmap.

8. crono Says:
   January 22nd, 2008 at 7:25 am

   Hi Gareth,

   very nice - thanks for the info

   bye

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