The document discusses using Scala and Spring Integration to implement Enterprise Integration Patterns. It provides an overview of messaging and integration concepts like pipes and filters, message channels, and message endpoints. It then explains how Spring Integration implements these patterns and supports configuration via XML or a Scala DSL. The Scala DSL offers benefits like compile-time validation and type safety compared to XML configuration.

1. Enterprise Integration Patterns
using
Scala and Spring Integration
Oleg Zhurakousky
SpringSource/VMware
Twitter: z_oleg
Email: ozhurakousky@vmware.com
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2. Enterprise Integration
Patterns (EIP)
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3. Messaging
• Integration starts with Messaging
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4. Why Messaging?
• Logical Decoupling
• Physical Decoupling
– Producer and Consumer are not aware of one
another
• Easy to extend
• Event-driven
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5. Pipes and Filters
– Endpoints (Filters) connected through
– Channels (Pipes) exchanging
– Message
$> cat foo.txt | grep the | while read l; do echo $l ; done
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6. Message
• Payload can be any object
• Header values are stored in a Map
Headers
Payload
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7. Message Channel
• Decouples Producers from Consumers
• Provides extension point for interceptors
• May be Point-to-Point
• Or Publish/Subscribe
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8. Message Endpoint
• Producers send Messages to a Message
Channel
• Depending on their type, Message Channels
may have Polling Consumers
• Or Event-Driven Consumers
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9. Message Endpoint Types
• Transformer
– Convert payload or modify headers
• Filter
– Discard messages based on boolean evaluation
• Router
– Determine next channel based on content
• Splitter
– Generate multiple messages from one
• Aggregator
– Assemble a single message from multiple
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10. What is Spring Integration?
• Framework is a reference implementation
of Enterprise Integration Patterns
• Built on top of Spring
– Runs within any Spring ApplicationContext
– All components are Spring-managed objects
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11. The Big Picture
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12. Spring Programming Model
• Inversion of Control
– Endpoints delegate to Spring-managed objects
– Framework handles message reception and
method invocation
• Clean separation of Code and Configuration
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13. Message Channel Types
<channel id="sync-p2p"/>
<channel id="async-p2p">
<dispatcher task-executor="someThreadPool" />
</channel>
<channel id="async-buffering-p2p">
<queue capacity="50" />
</channel>
<publish-subscribe-channel id="sync-pubsub" />
<publish-subscribe-channel id="async-pubsub"
task-executor="someThreadPool" />
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14. Messaging Endpoints
<int:gateway service-interface="foo.bar.MyGateway"
default-request-channel="inChannel" />
<int:filter input-channel="inChannel"
expression="payload.equals('World')"
output-channel="transformingChannel" />
<channel id="transformingChannel">
<dispatcher task-executor="executor" />
</channel>
<int:transformer input-channel="transformingChannel"
expression="'Hello ' + payload"
output-channel="loggingChannel" />
<int:service-activator input-channel="loggingChannel"
expression="T(java.lang.System).out.println(payload)"/>
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15. Channel Adapters and
Messaging Gateways
• JMS • HTTP (REST)
• AMQP • RIA (Flex, AJAX)
• TCP/UDP • WS (SOAP/POX)
• File/Resource • Mail (POP3/IMAP/SMTP)
• RMI • JDBC
• RSS/ATOM • XMPP
• FTP/FTPS/SFTP • Twitter
• NoSQL(Mongo, • Spring Events
Redis) • BPMN 2.0 (Activiti)
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16. Tooling
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17. Where does Scala fit in?
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18. Why Scala?
• There are 2 types of people in this world
– Like to say - "Don't like XML"
– "Don't like XML" - but understand that its
necessary evil. Appreciate alternatives but
not overly concerned with the lack of.
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19. Is XML or not to XML enough of an
argument?
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20. Why Scala? (cont. . .)
• True Type Safety vs IDE-Specific support
• Typos and misconfiguration
• Adding value based on the language features
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21. Welcome to SI Scala DSL
val messageFlow =
filter.using{p:String => p.equals("Cool World")} -->
transform.using{p:String => "Goodbye " + p} -->
handle.using{p:String => println(p)}
messageFlow.sendAndReceive[String]("Cool World")
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22. Welcome to SI Scala DSL
• Compile time validation vs initialization
validation and type safety:
filter.using{p:String => "Cool World"} - (filter can *only* return Boolean)
type mismatch; found : String => java.lang.String required: Function1[_, Boolean]
transform.using{p:String => println} - (transformer *must* return non-Unit value)
handle.using{p:String => println(p)} -->
handle.using{p:String => println(p)}
- value --> is not a member of o.s.i.d.SendingIntegrationComposition
(the first handler returns Unit (nothing of value in Messaging terms therefore the flow
can't continue)
Etc. . .
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23. Relevant Info
• Enterprise Integration Patterns - http://www.eaipatterns.com/
• Spring Integration project home -
http://www.springsource.org/spring-integration
• Spring Integration Scala DSL home -
https://github.com/SpringSource/spring-integration-scala/wiki
• Spring Integration Scala DSL blog -
http://blog.springsource.org/2012/03/05/introducing-spring-integration-
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