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From Yoryos <valo...@gmail.com>
Subject Re: Etags vs Week Etags
Date Thu, 04 Sep 2008 07:08:14 GMT
On Wed, Sep 3, 2008 at 11:09 PM, Johnny Kewl <john@kewlstuff.co.za> wrote:

>
> ----- Original Message ----- From: "Johnny Kewl" <john@kewlstuff.co.za>
> To: "Tomcat Users List" <users@tomcat.apache.org>
> Sent: Wednesday, September 03, 2008 9:51 PM
>
> Subject: Re: Etags vs Week Etags
>
>
>
>> ----- Original Message ----- From: "Yoryos" <valotas@gmail.com>
>> To: "Tomcat Users List" <users@tomcat.apache.org>
>> Sent: Wednesday, September 03, 2008 8:57 PM
>> Subject: Re: Etags vs Week Etags
>>
>>
>>  On Wed, Sep 3, 2008 at 8:12 PM, Johnny Kewl <john@kewlstuff.co.za>
>>> wrote:
>>>
>>>
>>>> Flipping good question... and I have a feeling that there is some
>>>> philosophy in the answer... reasons for the way it done...
>>>> The short answer is that you cant (I think)... the default servlet makes
>>>> em
>>>> weak (thats the philamamasomamy)...
>>>> That first section (strong) does nothing... the reason is that the
>>>> setEtag
>>>> method is there but as far as i can tell, never ever called by anything
>>>> in
>>>> Tomcat.
>>>> Its a hook...
>>>>
>>>> But stay calm... there are ways...
>>>>
>>>> This clever guy did this...
>>>>
>>>>
>>>> http://blog.bcarlso.net/articles/2007/10/19/tomcat-weak-etags-and-javascript-css-caching
>>>>
>>>> He is basically overriding the default servlet stuff to get things
>>>> done....
>>>> its smart, he knows his tomcat, but personally I dont like it...
>>>>
>>>> I think the generic problem is that a static resource cant control its
>>>> Etag... its a dumb image, and secondly no matter what a web server does,
>>>> another web server is going to do it different, so strong loses its
>>>> meaning
>>>> (more philamamasomamy)... or more simply, you just got to do it
>>>> yourself...
>>>>
>>>> I would prefer (or try, I havnt giving this a go)... make a little
>>>> servlet,
>>>> set the Etag headers yourself, map it to all the static resources you
>>>> want
>>>> to control...
>>>> And then do what you have to
>>>>
>>>> getContentLength() + "-" + getLastModified() + IncludeFiles() +
>>>> IncludedImages() + WhateEver() "\"";
>>>>
>>>> etc... I think thats easiest...
>>>>
>>>> The philamamasomamy on why TC chose to make it weak would be interesting
>>>> to
>>>> hear, but I do think that any serious scheme... on its way to some kind
>>>> of
>>>> private RSS system... will be doing its own thing.
>>>>
>>>> Have fun... nice question
>>>>
>>>>

Well can anyone also explain to me the first if block of code here:

    public String getETag(boolean strong) {
        String result = null;
        if (attributes != null) {
            Attribute attribute = attributes.get(ETAG);
            if (attribute != null) {
                try {
                    result = attribute.get().toString();
                } catch (NamingException e) {
                    ; // No value for the attribute
                }
            }
        }
        if (strong) {
            // The strong ETag must always be calculated by the resources
            result = strongETag;
        } else {
            // The weakETag is contentLenght + lastModified
            if (weakETag == null) {
                weakETag = "W/\"" + getContentLength() + "-"
                    + getLastModified() + "\"";
            }
            result = weakETag;
        }
        return result;
    }


I think it is not realy needed!

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