Asynchronous Communication Between Components Presented By: Sachin Singh

Characteristics of Synchronous Communication  The remote object must currently be alive.  The client must establish a connection to the object.  The client must invoke a method on the object, and wait while the remote object executes the method and returns the result, if any.

Real Life Business Applications  Applications distributed across heterogeneous platforms over the network  Networks/Components prone to failure  Dynamic Business needs- scalable architecture  Requirement  “Loose Coupling”

Message Oriented Middleware  Rather than connecting directly to a remote object, the client connects to the message-oriented middleware and sends its message.  MOM middleware is an event-driven, asynchronous, non-blocking and message-based communication method that guarantees message delivery.

Quote Every DAD needs a MOM. Every DAD needs a MOM. --The Message Oriented Middleware Consortium Interpretation? ? ? Every Distributed Application Development needs a Message- Oriented Middleware.

MOM Products  MSMQ (Microsoft Message Queuing)  IBM MQSeries  JMS (Java Message Services)

MOM Typical Architecture

The JMS Case  The Java Message Service (JMS) provides a standard Java-based interface to the message services of a MOM of some other provider.

JMS Characteristics Messaging Messaging loosely coupled communication loosely coupled communication sender/receiver do not have to be active at the same time sender/receiver do not have to be active at the same time Sender/receiver only have to agree on message format Sender/receiver only have to agree on message format Applications Applications no dependency on interfaces no dependency on interfaces components which may be disconnected (e.g. mobile phones) components which may be disconnected (e.g. mobile phones)

JMS API Architecture A JMS provider is a messaging system that implements the JMS interfaces and provides administrative and control features. J2EE platform release 1.3 JMS clients are the programs or components, written in the Java programming language, that produce and consume messages. Messages are the objects that communicate information between JMS clients. Administered objects are pre configured JMS objects created by an administrator for the use of clients. (Ex destinations and connection factories)

JMS – Publish/Subscribe Messaging Domain

Advantages  High-level abstraction  physical location/ physical details hidden  Interoperability  Portability  Flexibility  Scalability  Reduces complexity

Disadvantages  Implementations are proprietary  Component can overwhelm other component

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