41 lines
2.1 KiB
ReStructuredText
41 lines
2.1 KiB
ReStructuredText
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Routing DSL Overview
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====================
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The Akka HTTP :ref:`http-low-level-server-side-api` provides a ``Flow``- or ``Function``-level interface that allows
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an application to respond to incoming HTTP requests by simply mapping requests to responses:
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.. includecode2:: ../../code/docs/http/scaladsl/HttpServerExampleSpec.scala
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:snippet: low-level-server-example
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While it'd be perfectly possible to define a complete REST API service purely by pattern-matching against the incoming
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``HttpRequest`` (maybe with the help of a few extractors in the way of `Unfiltered`_) this approach becomes somewhat
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unwieldy for larger services due to the amount of syntax "ceremony" required. Also, it doesn't help in keeping your
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service definition as DRY_ as you might like.
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As an alternative Akka HTTP provides a flexible DSL for expressing your service behavior as a structure of
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composable elements (called :ref:`Directives`) in a concise and readable way. Directives are assembled into a so called
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*route structure* which, at its top-level, forms a handler ``Flow`` (or, alternatively, an async handler function) that
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can be directly supplied to a ``bind`` call.
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For example, the service definition from above, written using the routing DSL, would look like this:
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.. includecode2:: ../../code/docs/http/scaladsl/HttpServerExampleSpec.scala
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:snippet: high-level-server-example
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The core of the Routing DSL becomes available with a single import::
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import akka.http.scaladsl.server.Directives._
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This example also relies on the pre-defined support for Scala XML with::
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import akka.http.scaladsl.marshallers.xml.ScalaXmlSupport._
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The very short example shown here is certainly not the best for illustrating the savings in "ceremony" and improvements
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in conciseness and readability that the Routing DSL promises. The :ref:`Long Example` might do a better job in this
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regard.
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For learning how to work with the Routing DSL you should first understand the concept of :ref:`Routes`.
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.. _Unfiltered: http://unfiltered.databinder.net/
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.. _DRY: http://en.wikipedia.org/wiki/Don%27t_repeat_yourself
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