Chapter 5 Designing the integration Layer Message Routing Message routing is used to handle the scenarios where a single logical service is interacting with multiple existing systems using the list of dynamically specified recipients. Message routing is used along with a splitter, where one processes the exchange if it contains multiple recipients, each of which may have to be processed in a different way; after processing, one combines the results of individual related exchanges using an aggregator. Message Construction and Transformation Event messaging is used to transfer events from one application to another application, which is identified by a correlation identifier that contains a return address and is handled by a request reply message. Messages are wrapped in an envelope so that the existing system participating in a messaging system can establish a secure message header encryption method. Content filter and claim check patterns deal with the volumes of data, where large messages are handled but one is interested only in few data items from the entire message. Integration Patterns Integration patterns are the solution to commonly occurring integration problems, which are mainly divided as channel pattern (how messages are transported across channels), routing pattern (how messages routed between sender and receiver), transformation pattern (transformation of messages as per sender and receiver), and endpoints (how messages are consumed and exposed). Pattern – Simple (Internal) Integration The publisher–subscriber design pattern ensures that multiple applications consume the message at a time. Information standardization is based on source and synchronization of target systems with data required for its processing. The main focus is to synchronize information based on business events, thus removing any processing delays and overcoming the pain of managing a batch window. 162