40 lines
1.6 KiB
ReStructuredText
40 lines
1.6 KiB
ReStructuredText
.. _-conditional-:
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conditional
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===========
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Wraps its inner route with support for Conditional Requests as defined
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by http://tools.ietf.org/html/draft-ietf-httpbis-p4-conditional-26.
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Signature
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---------
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.. includecode2:: /../../akka-http-scala/src/main/scala/akka/http/scaladsl/server/directives/CacheConditionDirectives.scala
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:snippet: conditional
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Description
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-----------
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Depending on the given ``eTag`` and ``lastModified`` values this directive immediately responds with
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``304 Not Modified`` or ``412 Precondition Failed`` (without calling its inner route) if the request comes with the
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respective conditional headers. Otherwise the request is simply passed on to its inner route.
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The algorithm implemented by this directive closely follows what is defined in `this section`__ of the
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`HTTPbis spec`__.
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All responses (the ones produces by this directive itself as well as the ones coming back from the inner route) are
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augmented with respective ``ETag`` and ``Last-Modified`` response headers.
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Since this directive requires the ``EntityTag`` and ``lastModified`` time stamp for the resource as concrete arguments
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it is usually used quite deep down in the route structure (i.e. close to the leaf-level), where the exact resource
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targeted by the request has already been established and the respective ETag/Last-Modified values can be determined.
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The :ref:`FileAndResourceDirectives` internally use the ``conditional`` directive for ETag and Last-Modified support
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(if the ``akka.http.routing.file-get-conditional`` setting is enabled).
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__ http://tools.ietf.org/html/draft-ietf-httpbis-p4-conditional-26#section-6
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__ https://datatracker.ietf.org/wg/httpbis/
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