2015-07-10 19:11:08 +02:00
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.. _marshalling-java:
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Marshalling & Unmarshalling
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===========================
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2015-07-14 17:43:22 +02:00
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"Marshalling" is the process of converting a higher-level (object) structure into some kind of lower-level
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representation (and vice versa), often a binary wire format. Other popular names for it are "Serialization" or
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"Pickling".
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In akka-http "Marshalling" means the conversion of an object of type T into an HttpEntity, which forms the entity body
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of an HTTP request or response (depending on whether used on the client or server side).
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Marshalling
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-----------
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On the server-side marshalling is used to convert a application-domain object to a response (entity). Requests can
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contain an ``Accept`` header that lists acceptable content types for the client. A marshaller contains the logic to
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negotiate the result content types based on the ``Accept`` and the ``AcceptCharset`` headers.
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Marshallers can be specified when completing a request with ``RequestContext.completeAs`` or by using the ``BasicDirectives.completeAs``
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directives.
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These marshallers are provided by akka-http:
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* Use :ref:`json-jackson-support-java` to create an marshaller that can convert a POJO to an ``application/json``
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response using jackson_.
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* Use ``Marshallers.toEntityString``, ``Marshallers.toEntityBytes``, ``Marshallers.toEntityByteString``,
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``Marshallers.toEntity``, and ``Marshallers.toResponse`` to create custom marshallers.
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Unmarshalling
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-------------
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On the server-side unmarshalling is used to convert a request (entity) to a application-domain object. This means
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unmarshalling to a certain type is represented by a ``RequestVal``. Currently, several options are provided to create
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an unmarshalling ``RequestVal``:
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* Use :ref:`json-jackson-support-java` to create an unmarshaller that can convert an ``application/json`` request
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to a POJO using jackson_.
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* Use the predefined ``Unmarshallers.String``, ``Unmarshallers.ByteString``, ``Unmarshallers.ByteArray``,
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``Unmarshallers.CharArray`` to convert to those basic types.
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* Use ``Unmarshallers.fromMessage`` or ``Unmarshaller.fromEntity`` to create a custom unmarshaller.
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.. _jackson: https://github.com/FasterXML/jackson
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