Enterprise Integration Patterns
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.
Pattern Index
There now follows a list of the Enterprise Integration Patterns from the book along with examples of the various patterns using Apache Camel
Messaging Systems
| Message Channel | How does one application communicate with another using messaging? |
| Message | How can two applications connected by a message channel exchange a piece of information? |
| Pipes and Filters | How can we perform complex processing on a message while maintaining independence and flexibility? |
| Message Router | How can you decouple individual processing steps so that messages can be passed to different filters depending on a set of conditions? |
| Message Translator | How can systems using different data formats communicate with each other using messaging? |
| Message Endpoint | How does an application connect to a messaging channel to send and receive messages? |
Messaging Channels
| Point to Point Channel | How can the caller be sure that exactly one receiver will receive the document or perform the call? |
| Publish Subscribe Channel | How can the sender broadcast an event to all interested receivers? |
| Dead Letter Channel | What will the messaging system do with a message it cannot deliver? |
| Guaranteed Delivery | How can the sender make sure that a message will be delivered, even if the messaging system fails? |
| Message Bus | What 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 Construction
| Event Message | How can messaging be used to transmit events from one application to another? |
| Request Reply | When an application sends a message, how can it get a response from the receiver? |
| Correlation Identifier | How does a requestor that has received a reply know which request this is the reply for? |
| Return Address | How does a replier know where to send the reply? |
Message Routing
| Content Based Router | How do we handle a situation where the implementation of a single logical function (e.g., inventory check) is spread across multiple physical systems? |
| Message Filter | How can a component avoid receiving uninteresting messages? |
| Dynamic Router | How can you avoid the dependency of the router on all possible destinations while maintaining its efficiency? |
| Recipient List | How do we route a message to a list of (static or dynamically) specified recipients? |
| Splitter | How can we process a message if it contains multiple elements, each of which may have to be processed in a different way? |
| Aggregator | How do we combine the results of individual, but related messages so that they can be processed as a whole? |
| Resequencer | How can we get a stream of related but out-of-sequence messages back into the correct order? |
| Composed Message Processor | How can you maintain the overall message flow when processing a message consisting of multiple elements, each of which may require different processing? |
| Scatter-Gather | How do you maintain the overall message flow when a message needs to be sent to multiple recipients, each of which may send a reply? |
| Routing Slip | How do we route a message consecutively through a series of processing steps when the sequence of steps is not known at design-time and may vary for each message? |
| Throttler | How can I throttle messages to ensure that a specific endpoint does not get overloaded, or we don't exceed an agreed SLA with some external service? |
| Sampling | How can I sample one message out of many in a given period to avoid downstream route does not get overloaded? |
| Delayer | How can I delay the sending of a message? |
| Load Balancer | How can I balance load across a number of endpoints? |
| Hystrix | To use Hystrix Circuit Breaker when calling an external service. |
| Service Call | To call a remote service in a distributed system where the service is looked up from a service registry of some sorts. |
| Multicast | How can I route a message to a number of endpoints at the same time? |
| Loop | How can I repeat processing a message in a loop? |
| Content Enricher | How do we communicate with another system if the message originator does not have all the required data items available? |
| Content Filter | How do you simplify dealing with a large message, when you are interested only in a few data items? |
| Claim Check | How can we reduce the data volume of message sent across the system without sacrificing information content? |
| Normalizer | How do you process messages that are semantically equivalent, but arrive in a different format? |
| Sort | How can I sort the body of a message? |
| Script | How do I execute a script which may not change the message? |
| Validate | How can I validate a message? |
Messaging Endpoints
| Messaging Mapper | How do you move data between domain objects and the messaging infrastructure while keeping the two independent of each other? |
| Event Driven Consumer | How can an application automatically consume messages as they become available? |
| Polling Consumer | How can an application consume a message when the application is ready? |
| Competing Consumers | How can a messaging client process multiple messages concurrently? |
| Message Dispatcher | How can multiple consumers on a single channel coordinate their message processing? |
| Selective Consumer | How can a message consumer select which messages it wishes to receive? |
| Durable Subscriber | How can a subscriber avoid missing messages while it's not listening for them? |
| Idempotent Consumer | How can a message receiver deal with duplicate messages? |
| Transactional Client | How can a client control its transactions with the messaging system? |
| Messaging Gateway | How do you encapsulate access to the messaging system from the rest of the application? |
| Service Activator | How can an application design a service to be invoked both via various messaging technologies and via non-messaging techniques? |
System Management
| ControlBus | How can we effectively administer a messaging system that is distributed across multiple platforms and a wide geographic area? |
| Detour | How can you route a message through intermediate steps to perform validation, testing or debugging functions? |
| Wire Tap | How do you inspect messages that travel on a point-to-point channel? |
| Message History | How can we effectively analyze and debug the flow of messages in a loosely coupled system? |
| Log | How can I log processing a message? |
For a full breakdown of each pattern see the Book Pattern Appendix