Chapter 3. Enterprise Integration Patterns

Table of Contents

Camel supports most of the Enterprise Integration Patterns from the excellent book of the same name by Gregor Hohpe and Bobby Woolf. Its a highly recommended book, particularly for users of Camel.

There now follows a list of the Enterprise Integration Patterns from the book along with examples of the various patterns using Apache Camel

 Message ChannelHow does one application communicate with another using messaging?
 MessageHow can two applications connected by a message channel exchange a piece of information?
 Pipes and FiltersHow can we perform complex processing on a message while maintaining independence and flexibility?
 Message RouterHow can you decouple individual processing steps so that messages can be passed to different filters depending on a set of conditions?
 Message TranslatorHow can systems using different data formats communicate with each other using messaging?
 Message EndpointHow does an application connect to a messaging channel to send and receive messages?

Messaging Channels

 Point to Point ChannelHow can the caller be sure that exactly one receiver will receive the document or perform the call?
 Publish Subscribe ChannelHow can the sender broadcast an event to all interested receivers?
 Dead Letter ChannelWhat will the messaging system do with a message it cannot deliver?
 Guaranteed DeliveryHow can the sender make sure that a message will be delivered, even if the messaging system fails?
 Message BusWhat is an architecture that enables separate applications to work together, but in a de-coupled fashion such that applications can be easily added or removed without affecting the others?

Message Routing

 Content Based RouterHow do we handle a situation where the implementation of a single logical function (e.g., inventory check) is spread across multiple physical systems?
 Message FilterHow can a component avoid receiving uninteresting messages?
 Recipient ListHow do we route a message to a list of dynamically specified recipients?
 SplitterHow can we process a message if it contains multiple elements, each of which may have to be processed in a different way?
 ResequencerHow can we get a stream of related but out-of-sequence messages back into the correct order?

Message Transformation

 Content EnricherHow do we communicate with another system if the message originator does not have all the required data items available?
 Content FilterHow do you simplify dealing with a large message, when you are interested only in a few data items?
 NormalizerHow do you process messages that are semantically equivalent, but arrive in a different format?

Messaging Endpoints

 Messaging MapperHow do you move data between domain objects and the messaging infrastructure while keeping the two independent of each other?
 Event Driven ConsumerHow can an application automatically consume messages as they become available?
 Polling ConsumerHow can an application consume a message when the application is ready?
 Competing ConsumersHow can a messaging client process multiple messages concurrently?
 Message DispatcherHow can multiple consumers on a single channel coordinate their message processing?
 Selective ConsumerHow can a message consumer select which messages it wishes to receive?
 Durable SubscriberHow can a subscriber avoid missing messages while it's not listening for them?
 Idempotent ConsumerHow can a message receiver deal with duplicate messages?
 Transactional ClientHow can a client control its transactions with the messaging system?
 Messaging GatewayHow do you encapsulate access to the messaging system from the rest of the application?
 Service ActivatorHow can an application design a service to be invoked both via various messaging technologies and via non-messaging techniques?

System Management

 Wire TapHow do you inspect messages that travel on a point-to-point channel?

For a full breakdown of each pattern see the Book Pattern Appendix