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https://issues.apache.org/jira/browse/AWF-71?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tony Stevenson moved DEFT-28 to AWF-71:
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Reporter: Niklas Gustavsson
Key: AWF-71 (was: DEFT-28)
Project: Apache AWF (was: Deft)
> Handle If-Modified-Since
> ------------------------
>
> Key: AWF-71
> URL: https://issues.apache.org/jira/browse/AWF-71
> Project: Apache AWF
> Issue Type: Bug
> Reporter: Niklas Gustavsson
>
> To avoid sending resources that don't need to be sent, thus saving bandwidth,
> HTTP 1.1 defines the If-Modified-Since: and If-Unmodified-Since: request
> headers. The former says "only send the resource if it has changed since this
> date"; the latter says the opposite. Clients aren't required to use them, but
> HTTP 1.1 servers are required to honor requests that do use them.
> Unfortunately, due to earlier HTTP versions, the date value may be in any of
> three possible formats:
> If-Modified-Since: Fri, 31 Dec 1999 23:59:59 GMT
> If-Modified-Since: Friday, 31-Dec-99 23:59:59 GMT
> If-Modified-Since: Fri Dec 31 23:59:59 1999
> Again, all time values in HTTP use Greenwich Mean Time (though try to be
> tolerant of non-GMT times). If a date with a two-digit year seems to be more
> than 50 years in the future, treat it as being in the past-- this helps with
> the millennium bug. In fact, do this with any date handling in HTTP 1.1.
> Although servers must accept all three date formats, HTTP 1.1 clients and
> servers must only generate the first kind.
> If the date in either of these headers is invalid, or is in the future,
> ignore the header.
> If, without the header, the request would result in an unsuccessful
> (non-200-level) status code, ignore the header and send the non-200-level
> response. In other words, only apply these headers when you know the resource
> would otherwise be sent.
> The If-Modified-Since: header is used with a GET request. If the requested
> resource has been modified since the given date, ignore the header and return
> the resource as you normally would. Otherwise, return a "304 Not Modified"
> response, including the Date: header and no message body, like
> HTTP/1.1 304 Not Modified
> Date: Fri, 31 Dec 1999 23:59:59 GMT
> [blank line here]
> The If-Unmodified-Since: header is similar, but can be used with any method.
> If the requested resource has not been modified since the given date, ignore
> the header and return the resource as you normally would. Otherwise, return a
> "412 Precondition Failed" response, like
> HTTP/1.1 412 Precondition Failed
> [blank line here]
> See: http://www.jmarshall.com/easy/http/#http1.1s8
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