Configuration of connectors to use data handlers
If a data handler is to run in the context of a connector,
you must configure the connector to use a data handler:
- A connector must have access to the data-handler meta-object
in order to instantiate a data handler.
Before invoking a data handler for the first time, a connector
sets a static property in the data handler base class to the name
of a top-level data-handler meta-object. From this top-level meta-object,
the data handler obtains its configuration information. Each time
the data handler is subsequently instantiated, the configuration
properties for that data handler instance are obtained. The data
handler must have access to this configuration information to do
its work.
- To instantiate the data handler, the connector must know either
the name for the data handler class or the MIME type of the data.
When a connector calls createHandler() to invoke a data handler, it passes in either the class name
or the MIME type for the data.
- If the connector passes in the MIME type, the createHandler() method checks the top-level data-handler meta-object for
an attribute whose name matches the MIME type. If a matching attribute
is found, the createHandler() method checks for the value of the ClassName attribute in the child meta-object that is associated with
the MIME type.
- If the connector passes in a class name, the createHandler() method instantiates a data handler of that class name.
If the connector does not pass in the correct class name or MIME
type, the instantiation process fails. For more information, see Identifying the data-handler class.
Connectors are configured to obtain this configuration information
in different ways. For example:
- The Adapter for XML has a configuration property, DataHandlerConfigMO, that specifies the name of the top-level meta-object. If
this property is not filled in, the connector cannot find the meta-object.
In addition, any top-level business object for the XML connector
must have a MimeType attribute that specifies the MIME type of the data in the
business object. The connector uses the MimeType attribute value to invoke the appropriate data handler.
- The Adapter for JText has its own configuration meta-object,
which has ClassName, DataHandlerConfigMO and MimeType attributes to specify the name of the class, data-handler
meta-object, and the MIME type for a file, respectively.
Other connectors may have different ways of configuring the use
of a data handler. See the adapter guide for the connector for more
information.
If the connector cannot find the data handler top-level meta-object,
or it cannot determine the class name or MIME type, then it cannot
create the data handler. Therefore, when you are configuring a connector
to use a data handler, be sure to:
- Determine how to configure the name of the top-level data-handler
meta-object for the connector. Make sure that the spelling of the
meta-object name is correct.
- Determine how to configure the MIME type. Make sure that the
MIME type is spelled correctly.
- Make sure that the top-level data-handler meta-object is in
the supported objects list for the connector.
- Make sure that the child meta-object for the data handler has
the value of the data handler class name (in the ClassName attribute) specified correctly.
