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eBooks from David Chappell
All books and eBooks by David Chappell:
Java Message Service
by David Chappell and Richard Mons...
Chapter 1 In this chapter: • Enterprise Messaging • The Java Message Service (JMS) 1 • Application Scenarios • RPC Versus Asynchronous Messaging Understanding the Messaging Paradigm 1: Computers and people can communicate by using messaging systems to exchange messages over electronic networks. The most ubiquitous messaging system today is email, which facilitates communication among people. While email is an impor- tant human-to-human messaging system, this book is not about email. Instead, this book is concerned with messaging systems that allow different software applica- tions to communicate with each other. These application-to-application messag- ing systems, when used in business systems, are generically referred to as enterprise messaging systems, or Message-Oriented Middleware (MOM). Enterprise messaging systems allow two or more applications to exchange informa- tion in the form of messages. A message, in this case, is a self-contained package of business data and network routing headers. The business data contained in
(2007)
Java Message Service
Creating Distributed Enterprise Applications
by Mark Richards, Richard Mons..., and David Chappell
In the preceding code, if the redelivered flag was set on the message, we invoked the processCompensatingTransaction method to reverse any persisted or cached changes as a result of the prior message processing. In our case, the call to processInterimMes sage really doesn’t do anything except add the message payload to an internal Array List. However, in a real-world application, the call to processInterimMessage would probably execute some business logic and place data in a database table in preparation for the next message. Upon failure of the client, the messages would be redelivered, and the processCompensatingTransaction would clean up or reinitialize any application- specific data that may have been left in an unclean state. This is a good argument for message autonomy. Each message should be self-contained. When multiple messages need to depend on each other, the application should be written like a finite state machine where the results of
(2009)
Enterprise Service Bus
1 Chapter 1 Introduction to the Enterprise Service Bus Across all industries, executives are demanding more value from their strategic business processes. What process is strategic to a given company may vary dramatically by indus- try, but a common theme is that CEOs want their IT organizations to measurably improve the flow of data and information driving key business decisions. Whether it’s a financial services firm seeking a competitive advantage by guaranteeing a higher vol- ume of faster foreign exchange trades, a retail chain looking to accelerate the flow of store data back to brand managers at corporate headquarters, or a building materials supplier striving to optimize order flow through a complex distribution chain, there are common and significant technical challenges to be overcome. Information is locked up in applications within different departments and organizations, and it is both time-con- suming and costly to pry that data loose. In short,
(2008)
