When Java™ was first introduced, most of the IT industry focused on its graphical user interface characteristics and the competitive advantage it offered in terms of distribution and platform independence. Today, the focus has broadened considerably: Java has been recognized as an excellent platform for creating enterprise solutions, specifically for developing distributed server-side applications. This shift has much to do with Java's emerging role as a universal language for producing implementation-independent abstractions for common enterprise technologies. The JDBC™ API is the first and most familiar example. JDBC provides a vendor-independent Java interface for accessing SQL relational databases. This abstraction has been so successful that it's difficult to find a relational database vendor that doesn't support JDBC. Java abstractions for enterprise technologies have expanded considerably to include JNDI ( Java Naming and Directory Interface™) for abstracting directory services, JMX ( Java Management Extensions) for abstracting access to computer devices on a network, and JMS™ ( Java Message Service) for abstracting access to different Message-Oriented Middleware products.
JMS has quickly become a de facto industry standard. In its second version, most enterprise messaging vendors now support the JMS specification, making for a large selection of JMS providers to choose from.
The Java Message Service is a Java API implemented by enterprise messaging vendors to provide Java applications with a common and elegant programming model that is portable across messaging systems. Enterprise messaging systems are used to send notification of events and data between software applications. There are two common programming models supported by the JMS API: publish-and-subscribe and point-to-point. Each model provides benefits and either or both may be implemented by JMS providers.
JMS and enterprise messaging systems provide Java developers with an asynchronous messaging system that allows systems to interact without requiring them to be tightly coupled. Messages can be delivered to systems that are not currently running and processed when it's convenient. The decoupled, asynchronous characteristics of enterprise messaging make JMS an extremely powerful and critical enterprise API. JMS is used by Java developers in Enterprise Application Integration, Business-to-Business (B2B) projects, and distributed computing in general.
As JMS quickly moves into the forefront as one of the most important J2EE technologies, understanding how JMS works and when to use it will become the hallmark of the most successful distributed computing professionals. Choosing to read this book to learn about JMS may be one of the smartest career moves you ever make.