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making_xml_profiles.rst

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Creating an XML profiles file

An XML file can contain several XML profiles. These XML profiles are defined within the <dds> element, and in turn, within the <profiles> XML elements. The possible topologies for the definition of XML profiles are specified in :ref:`rootedvsstandalone`.

It is worth mentioning that the first element of the xml profile must have the xmlns attribute with the link xmlns="http://www.eprosima.com/XMLSchemas/fastRTPS_Profiles", in both rooted or standalone definitions. That link defines the reference of the xsd schema that the xml document complies with.

The available profile types are:

The following sections will show implementation examples for each of these profiles.

.. literalinclude:: /../code/XMLTesterSkipValidation.xml
    :language: xml
    :start-after: <!-->CREATING_XML_PROFILES<-->
    :end-before: <!--><-->

Note

The :ref:`examplexml` section shows an XML file with all the possible configurations and profile types. This example is useful as a quick reference to look for a particular property and how to use it. The Fast DDS XSD scheme can be used as a quick reference too.

Loading and applying profiles

In case the user defines the |Entity-api| profiles via XML files, it is required to load these XML files using the |DomainParticipantFactory::load_XML_profiles_file-api| public member function before creating any entity. It is also possible to load directly the XML information as a string data buffer using the |DomainParticipantFactory::load_XML_profiles_string-api| public member function. Moreover, |DomainParticipantFactory::create_participant_with_profile-api|, |DomainParticipant::create_publisher_with_profile-api|, |DomainParticipant::create_subscriber_with_profile-api|, |Publisher::create_datawriter_with_profile-api|, and |Subscriber::create_datareader_with_profile-api| member functions expect a profile name as an argument. Fast DDS searches the given profile name over all the loaded XML profiles, applying the profile to the entity if founded.

.. literalinclude:: /../code/DDSCodeTester.cpp
    :language: cpp
    :start-after: //XML-LOAD-APPLY-PROFILES
    :end-before: //!--
    :dedent: 8

Warning

It is worth mentioning that if the same XML profile file is loaded multiple times, the second loading of the file will result in an error together with the consequent error log.

Note

To load dynamic types from XML files see the :ref:`Usage` subsection of :ref:`xmldynamictypes`.

Rooted vs Standalone profiles definition

Fast DDS offers various options for the definition of XML profiles. These options are:

  • Stand-alone: The element defining the XML profile is the root element of the XML file. Elements <dds>, <profiles>, <library_settings>, <types>, and <log> can be defined in a stand-alone manner.
  • Rooted: The element defining the XML profile is the child element of another element. For example, the <participant>, <data_reader>, <data_writer>, <topic>, and <transport_descriptors> elements must be defined as child elements of the <profiles> element.

The following is an example of the definition of the <types> XML profile using the two previously discussed approaches.

Stand-alone 
.. literalinclude:: /../code/XMLTesterSkipValidation.xml
   :language: xml
   :start-after: <!-->STANDALONE_TYPES_START<-->
   :end-before: <!-->STANDALONE_TYPES_END<-->
Rooted 
.. literalinclude:: /../code/XMLTesterSkipValidation.xml
   :language: xml
   :start-after: <!-->ROOTED_TYPES_START<-->
   :end-before: <!-->ROOTED_TYPES_END<-->

Note

Make sure that the first element of the xml profile must have the xmlns tag with the link xmlns="http://www.eprosima.com/XMLSchemas/fastRTPS_Profiles", in both rooted or standalone definitions.

Modifying predefined XML profiles

Some scenarios may require to modify some of the QoS after loading the XML profiles. For such cases the :ref:`dds_layer_core_entity_types` which act as factories provide methods to get the QoS from the XML profile. This allows the user to read and modify predefined XML profiles before applying them to a new entity.

.. literalinclude:: /../code/DDSCodeTester.cpp
    :language: cpp
    :start-after: //XML-MIX-WITH-CODE
    :end-before: //!--
    :dedent: 8