Enterprise Integration Patterns
Messaging Patterns
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Event MessageEvent MessageMessaging Patterns » Message Construction

Several applications would like to use event-notification to coordinate their actions, and would like to use Messaging to communicate those events.

How can messaging be used to transmit events from one application to another?

Use an Event Message for reliable, asynchronous event notification between applications.

When a subject has an event to announce, it will create an event object, wrap it in a message, and send it on a channel. The observer will receive the event message, get the event, and process it. Messaging does not change the event notification, just makes sure that the notification gets to the observer.

The difference between an Event Message and a Document Message is a matter of timing and content. An event’s contents is typically less important. Many events are empty; their mere occurrance tells the observer to react. An event’s timing is very important; the subject should issue an event as soon as a change occurs, and the observer should process it quickly while it’s still relevant. Guaranteed Delivery is usually not very helpful with events because they’re frequent and need to be delivered quickly. Message Expiration can be very helpful to make sure that an event is processed quickly or not at all.

... Read the entire pattern in the book Enterprise Integration Patterns

Related patterns: Command Message, Document Message, Durable Subscriber, Remote Procedure Invocation, Guaranteed Delivery, Message, Message Expiration, Messaging, JMS Publish/Subscribe Example, Point-to-Point Channel, Publish-Subscribe Channel


Table of Contents
Preface
Introduction
Solving Integration Problems using Patterns
Integration Styles
File Transfer
Shared Database
Remote Procedure Invocation
Messaging
Messaging Systems
Message Channel
Message
Pipes and Filters
Message Router
Message Translator
Message Endpoint
Messaging Channels
Point-to-Point Channel
Publish-Subscribe Channel
Datatype Channel
Invalid Message Channel
Dead Letter Channel
Guaranteed Delivery
Channel Adapter
Messaging Bridge
Message Bus
Message Construction
Command Message
Document Message
Event Message
Request-Reply
Return Address
Correlation Identifier
Message Sequence
Message Expiration
Format Indicator
Interlude: Simple Messaging
JMS Request/Reply Example
.NET Request/Reply Example
JMS Publish/Subscribe Example
Message Routing
Content-Based Router
Message Filter
Dynamic Router
Recipient List
Splitter
Aggregator
Resequencer
Composed Msg. Processor
Scatter-Gather
Routing Slip
Process Manager
Message Broker
Message Transformation
Envelope Wrapper
Content Enricher
Content Filter
Claim Check
Normalizer
Canonical Data Model
Interlude: Composed Messaging
Synchronous (Web Services)
Asynchronous (MSMQ)
Asynchronous (TIBCO)
Messaging Endpoints
Messaging Gateway
Messaging Mapper
Transactional Client
Polling Consumer
Event-Driven Consumer
Competing Consumers
Message Dispatcher
Selective Consumer
Durable Subscriber
Idempotent Receiver
Service Activator
System Management
Control Bus
Detour
Wire Tap
Message History
Message Store
Smart Proxy
Test Message
Channel Purger
Interlude: Systems Management Example
Instrumenting Loan Broker
Integration Patterns in Practice
Case Study: Bond Trading System
Concluding Remarks
Emerging Standards
Appendices
Bibliography
Revision History
Creative Commons Attribution License

You can reuse the following elements under the Creative Commons Attribution license: pattern icon, pattern name, problem and solution statements (in bold), and the sketch. Other portions are protected by copyright.

Enterprise Integration Patterns

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