Event dictionaries
provide the ability to store data attributes in a easily
accessible way. They allow you to describe any number
of message properties in a flexible way.
An example of that would be a message selector where
the Nirvana Realm Server can use it to create a filter
that is based on metadata, so it is not necessary to
open the whole message in order to see if it should
be filtered or not.
Event dictionaries are implemented in Nirvana using
the nEventProperties class. They are quite similar to
a Hashtable except that primitive types can be added.
The nConsumeEvent event object can be constructed using
an nEventProperties object. as
Dictionaries can contain nested dictionaries and arrays
of dictionaries. Nirvana filtering
allows subscribers to filter based on the contents of
these inner sets of properties using our advanced
filtering capabilities.
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So if for example you were to publish an event containing
the definition of a bond with a bondname of bond1 and
you wanted to have a dictionary entry called BONDNAME
specifying that you would do:
nEventProperteis props =new nEventProperties();
props.put(“BONDNAME”,”bond1”);
nConsumeEvent e=new nConsumeEvent(props,myBondDefinition.getBytes());
myChannel.publish(e);
OR
nEventProperteis props =new nEventProperties();
props.put(“BONDNAME”,”bond2”);
nConsumeEvent e=new nConsumeEvent(props,myBondDefinition.getBytes());
myQueue.push(e);
For further information on the use of event dictionaries
please see the filtering
documentation. Specific for channels, please see more
info on how to create channel
keys.
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