6.14 Message Broker
Message Broker [EIP] is an EAI architectural style wherein a component of a messaging system implements centralized routing for all messages flowing through the system. [EIP] also uses the term hub-and-spoke when referring to this architectural style. SeeBeyond's DataGate 3.6 product, predecessor to eGate 4.x, ICAN 5.0, and Java CAPS 5.1, is a Message Broker–based EAI package.
Message Broker architecture allows decoupling of senders from receivers. The senders need not know where the messages are going, and receivers need not know from where the messages are coming. The Message Broker embeds all routing logic necessary to get messages from senders to receivers. This centralizes routing logic maintenance.
In Java CAPS, and ICAN before it, each connectivity map could be considered to represent a Message Broker–based solution. In effect, all collaborations and Business Processes present in a connectivity map route messages from sources to destinations. Each eInsight Business Process could also be considered a Message Broker implementation, as it, too, makes routing decisions when orchestrating a series of activities. Collections of connectivity maps sharing common channels could be considered hierarchies of Message Brokers [EIP].
While Java CAPS can certainly be used to implement centralized routing solutions in the spirit of Message Broker, doing so does not appear particularly necessary or particularly advantageous.