Databases Reference
In-Depth Information
format. All the delivery details can be hidden under the covers. EDN uses JMS to
deliver events from subscribers to publishers, but the configuration of JMS queues
and topics and any associated filters is hidden from users of the EDN service.
The following table highlights the differences between traditional MOM and
EDN. As can be seen, the focus of EDN is to make it very easy for event producers
to publish an event that can then be received by an arbitrary number of event
subscribers. EDN developers only need to be aware of the events themselves,
as all the underlying delivery mechanisms are taken care of within the EDN.
Interaction
Pattern
Messaging Support Configuration
EDN Notes
Request/Reply
Separate JMS queues
are used for Request
and Response
messages. JMS
Message Headers
are used to correlate
requests with
responses.
Request and
response queues
must be configured
with appropriate
connection factories
and message store.
EDN does not support
request/reply. It is not
possible to target the
receiver of an event.
Event subscribers are
not visible to event
producers and so
cannot be directly
targeted. Similarly,
event producers are
not visible to event
subscribers and so it
is not possible to send
direct replies just to the
originator of the event.
One way
guaranteed
delivery
Single JMS queue
with a single
subscriber
Queue must be
configured with
appropriate
connection factory
and message store
EDN does not support
guaranteed one way
delivery of events. An
event producer has no
way of knowing how
many subscribers will
receive the message or
if any subscribers will
receive the message.
One-to-many
message
delivery
Single JMS topic
with zero or more
subscribers
Topic must be
configured with
appropriate
connection factory
and message store.
EDN supports
exactly this message
interaction pattern
without the need to
configure any JMS
artifacts. EDN uses
JMS but this is hidden
from the developer.
