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this article explores certain approaches that will result in a robust integration solution.
messaging technology is designed to deal with requirements. home-grown solutions can face significant challenges to meet these needs.
the rest of this article will deal with ibms websphere mq as the messaging product. the principles described here apply to any messaging product.
most integration systems are given these nfrs. applications being integrated may not be running at all times. the network layer between the systems may not be available at all times. the same message may not be processed twice (unless a message is being retried due to earlier failure in processing). information sent to an application must belong to a transaction along with other activities, such as database updates. the information should be sent only if all of those activities go through.
the principles of messaging
a message sent to a system will be delivered on a best effort basis. systems cannot ensure delivery within a specific time period. for immediate delivery, consider using a synchronous technology, such as enterprise javabeans (ejb).websphere mq client-based programs can also do an immediate delivery of messages. in this case, the application connects to a remote queue manager using tcp/ip and sends the message directly to a queue in the remote queue manager. in both cases, we fail to meet nfr #2.
do not assume that there is only one receiver process 【程序编程相关:Integrating XSL-FO i】
most developers are trained to write synchronous applications. in the popular programming languages, method calls are inherently synchronous in nature. messaging requires a different way of thinking. to help the developers understand the uniqueness of messaging, i have the following maxims.do not assume timeliness of message delivery 【推荐阅读:Product Review: Styl】
there may be more than one process picking and processing messages from a single queue. websphere mq ensures that a message is delivered to one process only. multiple receiver processes are run for scalability reasons. we can process more messa... 下一页