=htp move docs and create TOC structure
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12 changed files with 66 additions and 49 deletions
4
akka-docs-dev/rst/scala/http/client.rst
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4
akka-docs-dev/rst/scala/http/client.rst
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Client API
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==========
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(todo)
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akka-docs-dev/rst/scala/http/https.rst
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akka-docs-dev/rst/scala/http/https.rst
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HTTPS
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=====
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Is not yet supported.
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(todo)
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12
akka-docs-dev/rst/scala/http/index-client-server.rst
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akka-docs-dev/rst/scala/http/index-client-server.rst
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.. _http-client-server-scala:
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HTTP Client & Server
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====================
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.. toctree::
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:maxdepth: 2
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model
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client
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server
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https
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18
akka-docs-dev/rst/scala/http/index-routing.rst
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akka-docs-dev/rst/scala/http/index-routing.rst
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.. _http-routing-index-scala:
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HTTP Routing
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============
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.. toctree::
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:maxdepth: 2
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quick-start
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routing
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directives
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rejections
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exception-handling
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path-matchers
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marshalling
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directives/alphabetically
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directives/by-trait
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8
akka-docs-dev/rst/scala/http/index-testkit.rst
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akka-docs-dev/rst/scala/http/index-testkit.rst
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.. _http-testkit-scala:
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HTTP TestKit
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============
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.. note::
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This part of the documentation has not yet been written, please stay tuned for updates.
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@ -1,17 +1,28 @@
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High-level HTTP API
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===================
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.. _http-scala:
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Akka HTTP
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=========
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The purpose of the Akka HTTP layer is to expose Actors to the web via HTTP and
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to enable them to consume HTTP services as a client. It is not an HTTP
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framework, it is an Actor-based toolkit for interacting with web services and
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clients. This toolkit is structured into several layers:
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* ``akka-http-core``: A complete implementation of the HTTP standard, both as
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client and server.
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* ``akka-http``: A convenient and powerful routing DSL for expressing web
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services.
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* ``akka-http-testkit``: A test harness and set of utilities for verifying
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your web service implementations.
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Additionally there are several integration modules with bindings for different
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serialization and deserialization schemes for HTTP entities.
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.. toctree::
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:maxdepth: 2
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quick-start
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routing
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directives
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rejections
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exception-handling
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path-matchers
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marshalling
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directives/alphabetically
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directives/by-trait
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index-client-server
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index-routing
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index-testkit
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156
akka-docs-dev/rst/scala/http/model.rst
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akka-docs-dev/rst/scala/http/model.rst
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.. _http-model-scala:
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Model
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=====
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The akka HTTP model contains a mostly immutable, case-class based model of the major HTTP data structures,
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like HTTP requests, responses and common headers. It also includes a parser for the latter, which is able to construct
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the more structured header models from raw unstructured header name/value pairs.
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Overview
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--------
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Since akka-http-core provides the central HTTP data structures you will find the following import in quite a
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few places around the code base (and probably your own code as well):
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.. includecode:: ../code/docs/http/ModelSpec.scala
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:include: import-model
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This brings in scope all of the relevant things that are defined here and that you’ll want to work with, mainly:
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- ``HttpRequest`` and ``HttpResponse``, the central message model
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- ``headers``, the package containing all the predefined HTTP header models and supporting types
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- Supporting types like ``Uri``, ``HttpMethods``, ``MediaTypes``, ``StatusCodes``, etc.
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A common pattern is that the model of a certain entity is represented by an immutable type (class or trait),
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while the actual instances of the entity defined by the HTTP spec live in an accompanying object carrying the name of
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the type plus a trailing plural 's'.
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For example:
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- Defined HttpMethod instances live in the HttpMethods object.
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- Defined HttpCharset instances live in the HttpCharsets object.
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- Defined HttpEncoding instances live in the HttpEncodings object.
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- Defined HttpProtocol instances live in the HttpProtocols object.
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- Defined MediaType instances live in the MediaTypes object.
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- Defined StatusCode instances live in the StatusCodes object.
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HttpRequest / HttpResponse
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--------------------------
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``HttpRequest`` and ``HttpResponse`` are the basic case classes representing HTTP messages.
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An ``HttpRequest`` consists of
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- method (GET, POST, etc.)
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- URI
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- protocol
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- headers
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- entity (body data)
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Here are some examples how to construct an ``HttpRequest``:
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.. includecode:: ../code/docs/http/ModelSpec.scala
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:include: construct-request
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All parameters of ``HttpRequest`` have default values set, so e.g. ``headers`` don't need to be specified
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if there are none. Many of the parameters types (like ``HttpEntity`` and ``Uri``) define implicit conversions
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for common use cases to simplify the creation of request and response instances.
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An ``HttpResponse`` consists of
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- status code
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- protocol
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- headers
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- entity
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Here are some examples how to construct an ``HttpResponse``:
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.. includecode:: ../code/docs/http/ModelSpec.scala
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:include: construct-response
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Aside from the simple ``HttpEntity`` constructors to create an entity from a fixed ``ByteString`` shown here,
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subclasses of ``HttpEntity`` allow data to be specified as a stream of data which is explained in the next section.
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.. _HttpEntity:
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HttpEntity
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----------
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An ``HttpEntity`` carries the content of a request together with its content-type which is needed to interpret the raw
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byte data.
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Akka HTTP provides several kinds of entities to support static and streaming data for the different kinds of ways
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to transport streaming data with HTTP. There are four subtypes of HttpEntity:
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HttpEntity.Strict
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An entity which wraps a static ``ByteString``. It represents a standard, non-chunked HTTP message with ``Content-Length``
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set.
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HttpEntity.Default
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A streaming entity which needs a predefined length and a ``Producer[ByteString]`` to produce the body data of
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the message. It represents a standard, non-chunked HTTP message with ``Content-Length`` set. It is an error if the
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provided ``Producer[ByteString]`` doesn't produce exactly as many bytes as specified. On the wire, a Strict entity
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and a Default entity cannot be distinguished. However, they offer a valuable alternative in the API to distinguish
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between strict and streamed data.
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HttpEntity.Chunked
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A streaming entity of unspecified length that uses `Chunked Transfer Coding`_ for transmitting data. Data is
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represented by a ``Producer[ChunkStreamPart]``. A ``ChunkStreamPart`` is either a non-empty ``Chunk`` or a ``LastChunk``
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containing optional trailer headers. The stream must consist of 0..n ``Chunked`` parts and can be terminated by an
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optional ``LastChunk`` part (which carries optional trailer headers).
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HttpEntity.CloseDelimited
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A streaming entity of unspecified length that is delimited by closing the connection ("Connection: close"). Note,
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that this entity type can only be used in an ``HttpResponse``.
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HttpEntity.IndefiniteLength
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A streaming entity of unspecified length that can be used as a ``BodyPart`` entity.
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Entity types ``Strict``, ``Default``, and ``Chunked`` are a subtype of ``HttpEntity.Regular`` which allows to use them for
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requests and responses. In contrast, ``HttpEntity.CloseDelimited`` can only be used for responses.
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Streaming entity types (i.e. all but ``Strict``) cannot be shared or serialized. To create a strict, sharable copy of an
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entity or message use ``HttpEntity.toStrict`` or ``HttpMessage.toStrict`` which returns a Future of the object with the
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body data collected into a ``ByteString``.
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.. _Chunked Transfer Coding: http://tools.ietf.org/html/draft-ietf-httpbis-p1-messaging-26#section-4.1
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The ``HttpEntity`` companion object contains several helper constructors to create entities from common types easily.
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You can pattern match over the subtypes of ``HttpEntity`` if you want to provide special handling for each of the
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subtypes. However, in many cases a recipient of an `HttpEntity` doesn't care about of which subtype an entity is
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(and how data is transported exactly on the HTTP layer). Therefore, a general ``HttpEntity.dataBytes`` is provided
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which allows access to the data of an entity regardless of its concrete subtype.
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.. note::
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When to use which subtype?
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- Use Strict if the amount of data is small and it is already in the heap (or even available as a ``ByteString``)
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- Use Default if the data is generated by a streaming data source and the size of the data is fixed
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- Use Chunked to support a data stream of unknown length
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- Use CloseDelimited for a response as an alternative to Chunked e.g. if chunked transfer encoding isn't supported
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by a client.
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- Use IndefiniteLength instead of CloseDelimited in a BodyPart.
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Header model
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------------
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Akka HTTP contains a rich model of the common HTTP headers. Parsing and rendering is done automatically so that
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applications don't need to care for the actual syntax of headers. Headers not modelled explicitly are represented
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as a ``RawHeader``.
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See these examples of how to deal with headers:
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.. includecode:: ../code/docs/http/ModelSpec.scala
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:include: headers
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Parsing / Rendering
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-------------------
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Parsing and rendering of HTTP data structures is heavily optimized and for most types there's currently no public API
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provided to parse (or render to) Strings or byte arrays.
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157
akka-docs-dev/rst/scala/http/server.rst
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157
akka-docs-dev/rst/scala/http/server.rst
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.. _http-core-server-scala:
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Server API
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==========
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The Akka HTTP server is an embedded, stream-based, fully asynchronous, low-overhead
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HTTP/1.1 server implemented on top of `Akka Streams`_. (todo: fix link)
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It sports the following features:
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- Full support for `HTTP persistent connections`_
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- Full support for `HTTP pipelining`_
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- Full support for asynchronous HTTP streaming including "chunked" transfer encoding accessible through an idiomatic
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reactive streams API
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- Optional SSL/TLS encryption
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.. _HTTP persistent connections: http://en.wikipedia.org/wiki/HTTP_persistent_connection
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.. _HTTP pipelining: http://en.wikipedia.org/wiki/HTTP_pipelining
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.. _Akka streams: http://akka.io/docs/
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Design Philosophy
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-----------------
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Akka HTTP server is scoped with a clear focus on the essential functionality of an HTTP/1.1 server:
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- Connection management
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- Parsing messages and headers
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- Timeout management (for requests and connections)
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- Response ordering (for transparent pipelining support)
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All non-core features of typical HTTP servers (like request routing, file serving, compression, etc.) are left to
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the next-higher layer in the application stack, they are not implemented by the HTTP server itself.
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Apart from general focus this design keeps the server small and light-weight as well as easy to understand and
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maintain.
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Basic Architecture
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------------------
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Akka HTTP server is implemented on top of Akka streams and makes heavy use of them - in its
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implementation and also on all levels of its API.
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On the connection level Akka HTTP supports basically the same interface as Akka streams IO: A socket binding is
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represented as a stream of incoming connections. The application needs to provide a ``Flow[HttpRequest, HttpResponse]``
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to "translate" requests into responses.
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Streaming is also supported for single message entities itself. Particular kinds of ``HttpEntity``
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subclasses provide support for fixed or streamed message entities.
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Starting and Stopping
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---------------------
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An Akka HTTP server is bound by invoking the ``bind`` method of the `akka.http.Http`_ extension:
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.. includecode:: ../code/docs/http/HttpServerExampleSpec.scala
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:include: bind-example
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Arguments to the ``Http.bind`` method specify the interface and port to bind to and register interest in handling incoming
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HTTP connections. Additionally, the method also allows you to define socket options as well as a larger number
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of settings for configuring the server according to your needs.
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The result of the ``bind`` method is a ``Http.ServerBinding`` which is immediately returned. The ``ServerBinding.connections``
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returns a ``Source[IncomingConnection]`` which is used to handle incoming connections. The actual binding is only done when this
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source is materialized as part of a bigger processing pipeline. In case the bind fails (e.g. because the port is already
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busy) the error will be reported by flagging an error on the ``IncomingConnection`` stream.
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After materialization ``ServerBinding.localAddress`` returns the actual local address of the bound socket.
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Connections are handled by materializing a pipeline which uses the ``Source[IncomingConnection]`` returned by
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``ServerBinding.connections``. The binding is released and the underlying listening socket is closed when all
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subscribers of the ``connections`` source have cancelled their subscription.
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(todo: explain even lower level serverFlowToTransport API)
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.. _akka.http.Http: @github@/akka-http-core/src/main/scala/akka/http/Http.scala
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Request-Response Cycle
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----------------------
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When a new connection has been accepted it will be published by by the ``ServerBinding.connections`` source as an
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``Http.IncomingConnection`` which consists of the remote address, and methods to provide a ``Flow[HttpRequest, HttpResponse]``
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to handle requests coming in over this connection.
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Requests are handled by calling one of the ``IncomingConnection.handleWithX`` methods with a handler, which can either be
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- a ``Flow[HttpRequest, HttpResponse]`` for ``handleWith``,
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- a function ``HttpRequest => HttpResponse`` for ``handleWithSyncHandler``,
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- or a function ``HttpRequest => Future[HttpResponse]`` for ``handleWithAsyncHandler``.
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.. includecode:: ../code/docs/http/HttpServerExampleSpec.scala
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:include: full-server-example
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In this case, a request is handled by transforming the request stream with a function ``HttpRequest => HttpResponse``
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using ``handleWithSyncHandler`` (or equivalently, Akka stream's ``map`` operator). Depending on the use case, arbitrary
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other ways of connecting are conceivable using Akka stream's combinators.
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If the application provides a ``Flow``, it is also the responsibility of the application to generate exactly one response
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for every request and that the ordering of responses matches the ordering of the associated requests (which is relevant
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if HTTP pipelining is enabled where processing of multiple incoming requests may overlap). Using ``handleWithSyncHandler``
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or ``handleWithAsyncHandler`` or, instead, if using stream operators like ``map`` or ``mapFuture`` this requirement
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will automatically be fulfilled.
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Streaming request/response entities
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Streaming of HTTP message entities is supported through subclasses of ``HttpEntity``. You need to be able to deal
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with streamed entities when receiving a request as well as when constructing responses. See :ref:`HttpEntity` for
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a description of the alternatives.
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(todo): Link to :ref:`http-routing-scala` for (un-)marshalling facilities.
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Closing a connection
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~~~~~~~~~~~~~~~~~~~~
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The HTTP connection will be closed when the handling ``Flow`` cancel its upstream subscription or the peer closes the
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connection.
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You can also use the value of the ``Connection`` header of a response as described below to give a hint to the
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implementation to close the connection after the completion of the response.
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HTTP Headers
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------------
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When the Akka HTTP server receives an HTTP request it tries to parse all its headers into their respective
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model classes. No matter whether this succeeds or not, the connection actor will always pass on all
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received headers to the application. Unknown headers as well as ones with invalid syntax (according to the header
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parser) will be made available as ``RawHeader`` instances. For the ones exhibiting parsing errors a warning message is
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logged depending on the value of the ``illegal-header-warnings`` config setting.
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Some common headers are treated specially in the model and in the implementation and should not occur in the ``headers``
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field of an HTTP message:
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- ``Content-Type``: Use the ``contentType`` field of the ``HttpEntity`` subclasses to set or determine the content-type
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on an entity.
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- ``Transfer-Encoding``: The ``Transfer-Encoding`` is represented by subclasses of ``HttpEntity``.
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- ``Content-Length``: The ``Content-Length`` header is represented implicitly by the choice of an ``HttpEntity`` subclass:
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A Strict entity determines the Content-Length by the length of the data provided. A Default entity has an explicit
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``contentLength`` field which specifies the amount of data the streaming producer will produce. Chunked and CloseDelimited
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entities don't need to define a length.
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- ``Server``: The ``Server`` header is usually added automatically and it's value can be configured. An application can
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decide to provide a custom ``Server`` header by including an explicit instance in the response.
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- ``Date``: The ``Date`` header is added automatically and can be overridden by supplying it manually.
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- ``Connection``: When sending out responses the connection actor watches for a ``Connection`` header set by the
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application and acts accordingly, i.e. you can force the connection actor to close the connection after having sent
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the response by including a ``Connection("close")`` header. To unconditionally force a connection keep-alive you can
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explicitly set a ``Connection("Keep-Alive")`` header. If you don't set an explicit ``Connection`` header the
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connection actor will keep the connection alive if the client supports this (i.e. it either sent a
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``Connection: Keep-Alive`` header or advertised HTTP/1.1 capabilities without sending a ``Connection: close`` header).
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SSL Support
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-----------
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(todo)
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