.. Services
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  #          Stephan Meissl <stephan.meissl@eox.at>
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.. _Services:

Services
========

This section deals with the creation of new Hervices handlers that allow to process OGC web service requests and are easily exposed via the :func:`ows 
<eoxserver.services.views.ows>` view.

Service Handlers are :class:`Components <eoxserver.core.component.Component>`
that at least implement the :class:`ServiceHandlerInterface
<eoxserver.services.ows.interfaces.ServiceHandlerInterface>`. For a Service
Handler to be fully accessible it is also necessary to implement either or both
of :class:`GetServiceHandlerInterface 
<eoxserver.services.ows.interfaces.GetServiceHandlerInterface>` and 
:class:`PostServiceHandlerInterface 
<eoxserver.services.ows.interfaces.PostServiceHandlerInterface>`.
For general information about Plugins/Components please refer to the 
:ref:`Plugins` documentation.


Initial Setup
-------------

Each service handler must provide the following:

  - The ``service`` the handler will contribute to
  - The ``versions`` of the ``service`` the handler is capable of responding to
  - The ``request`` of the ``service`` the handler is able to respond
  - a ``handle`` method that takes a :class:`django.http.HttpRequest` as 
    parameter

A service handler *can* provide an ``index``, which allows the sorting of
the handlers in a "GetCapabilities" response.

The following is an example handler for the "GetCapabilities" handler of the
fictional ``WES`` (Web Example Service):
::

    from eoxserver.core import Component, implements, ExtensionPoint
    from eoxserver.services.ows.interfaces import (
        ServiceHandlerInterface, GetServiceHandlerInterface,
        PostServiceHandlerInterface
    )

    class WESGetCapabilitiesHandler(Component):
        implements(ServiceHandlerInterface)
        implements(GetServiceHandlerInterface)
        implements(PostServiceHandlerInterface)

        service = "WES"
        request = "GetCapabilities"
        versions = ["1.0"]

        def handle(self, request):
            ...

.. note:: A word about versions: in EOxServer they are represented by the
   :class:`Version <eoxserver.services.version.Version>` class. It follows OGC
   conventions on treating versions. So for example the versions "1.0" and 
   "1.0.1" are considered equal. For our example this means that our handler
   will be able to respond to any request with a version "1.0.x".