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.
There now follows a list of the Enterprise Integration Patterns from the book along with examples of the various patterns using Apache Camel
How does one application communicate with another using messaging?
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?
How can you decouple individual processing steps so that messages can be passed to different filters depending on a set of conditions?
How can systems using different data formats communicate with each other using messaging?
How does an application connect to a messaging channel to send and receive messages?
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?
How can the sender make sure that a message will be delivered, even if the messaging system fails?
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?
How can messaging be used to transmit events from one application to another?
When an application sends a message, how can it get a response from the receiver?
How does a requestor that has received a reply know which request this is the reply for?
How does a replier know where to send the reply?
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?
How can a component avoid receiving uninteresting messages?
How can you avoid the dependency of the router on all possible destinations while maintaining its efficiency?
How do we route a message to a list of (static or dynamically) specified recipients?
How can we process a message if it contains multiple elements, each of which may have to be processed in a different way?
How do we combine the results of individual, but related messages so that they can be processed as a whole?
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?
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?
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?
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?
How can I sample one message out of many in a given period to avoid downstream route does not get overloaded?
How can I delay the sending of a message?
How can I balance load across a number of endpoints?
To use Hystrix Circuit Breaker when calling an external service.
To call a remote service in a distributed system where the service is looked up from a service registry of some sorts.
How can I route a message to a number of endpoints at the same time?
How can I repeat processing a message in a loop?
How do we communicate with another system if the message originator does not have all the required data items available?
How do you simplify dealing with a large message, when you are interested only in a few data items?
How can we reduce the data volume of message sent across the system without sacrificing information content?
How do you process messages that are semantically equivalent, but arrive in a different format?
How can I sort the body of a message?
How do I execute a script which may not change the message?
How can I validate a message?
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?
How can an application consume a message when the application is ready?
How can a messaging client process multiple messages concurrently?
How can multiple consumers on a single channel coordinate their message processing?
How can a message consumer select which messages it wishes to receive?
How can a subscriber avoid missing messages while it's not listening for them?
How can a message receiver deal with duplicate messages?
How can a client control its transactions with the messaging system?
How do you encapsulate access to the messaging system from the rest of the application?
How can an application design a service to be invoked both via various messaging technologies and via non-messaging techniques?
How can we effectively administer a messaging system that is distributed across multiple platforms and a wide geographic area?
How can you route a message through intermediate steps to perform validation, testing or debugging functions?
How do you inspect messages that travel on a point-to-point channel?
How can we effectively analyze and debug the flow of messages in a loosely coupled system?
How can I log processing a message?
For a full breakdown of each pattern see the Book Pattern Appendix