Caching static content -> Bug in Filter implementation?

[ju...@entory.com]

Hello

I do some further analysis in this problem and got following result:

Precondition: The filter manipulates the HTTP header when returning a
static resource (e.g. image).

HTTP 200
In case of a HTTP 200 (OK) result the header is not added when the doFilter
method is like following:
....
filterChain.doFilter(request, response);
response.setHeader(name, value);
....

In contrast to it works when the code is like following:
....
response.setHeader(name, value);
filterChain.doFilter(request, response);
....

In other words: When returning a HTTP 200 (OK) I must set the header before
forwarding the request to the next filter.

HTTP 304
In this case it doesn't mention whether setting the header is before or
after forwarding the request.

Any comments?

Jürgen Dufner


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Re: Caching static content -> Bug in Filter implementation?

[Jon Wingfield <jo...@mkodo.com>]

I think that's expected behaviour: You can't set headers after the 
response has been committed (more body data has been written to the 
outputstream than the buffer size).

In the case of the 200 response code the call to 
filterChain.doFilter(...) actually serves the content. Setting of the 
header after this is too late.

Jon

juergen.dufner@entory.com wrote:
> Hello
> 
> I do some further analysis in this problem and got following result:
> 
> Precondition: The filter manipulates the HTTP header when returning a
> static resource (e.g. image).
> 
> HTTP 200
> In case of a HTTP 200 (OK) result the header is not added when the doFilter
> method is like following:
> ....
> filterChain.doFilter(request, response);
> response.setHeader(name, value);
> ....
> 
> In contrast to it works when the code is like following:
> ....
> response.setHeader(name, value);
> filterChain.doFilter(request, response);
> ....
> 
> In other words: When returning a HTTP 200 (OK) I must set the header before
> forwarding the request to the next filter.
> 
> HTTP 304
> In this case it doesn't mention whether setting the header is before or
> after forwarding the request.
> 
> Any comments?
> 
> Jürgen Dufner
> 
> 
> -----------------------------------------
> Diese E-Mail enthaelt vertrauliche oder rechtlich geschuetzte
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> Kopieren
> dieser E-Mail oder die unbefugte Weitergabe der enthaltenen
> Informationen
> ist nicht gestattet.
> 
> The information contained in this message is confidential or protected
> by
> law. If you are not the intended recipient, please contact the sender
> and
> delete this message. Any unauthorised copying of this message or 
> unauthorised distribution of the information contained herein is
> prohibited.
> 
> 
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