Enterprise Integration PatternsMessaging Patterns

Service ActivatorService Activator

Messaging Patterns

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An application has a service that it would like to make available to other applications.

How can an application design a service to be invoked both via various messaging technologies and via non-messaging techniques?

Design a Service Activator that connects the messages on the channel to the service being accessed.

A Service Activator can be one-way (request only) or two-way (Request-Reply). The service can be as simple as a method call—synchronous and non-remote—perhaps part of a Service Layer [EAA]. The activator can be hard-coded to always invoke the same service, or can use reflection to invoke the service indicated by the message. The activator handles all of the messaging details and invokes the service like any other client, such that the service doesn’t even know it’s being invoked through messaging.


Related patterns: Command Message, Competing Consumers, Event-Driven Consumer, Invalid Message Channel, Message Dispatcher, Message Endpoint, Messaging Gateway, Polling Consumer, Request-Reply, Transactional Client

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Enterprise Integration Patterns Find the full description of this pattern in:
Enterprise Integration Patterns
Gregor Hohpe and Bobby Woolf
ISBN 0321200683
650 pages
Creative Commons Attribution License Parts of this page are made available under the Creative Commons Attribution license. You can reuse the pattern icon, the pattern name, the problem and solution statements (in bold), and the sketch under this license. Other portions of the text, such as text chapters or the full pattern text, are protected by copyright.

Table of Contents
Solving Integration Problems using Patterns
Integration Styles
File Transfer
Shared Database
Remote Procedure Invocation
Messaging Systems
Message Channel
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
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
Composed Msg. Processor
Routing Slip
Process Manager
Message Broker
Message Transformation
Envelope Wrapper
Content Enricher
Content Filter
Claim Check
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
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
Revision History