We are living in a connected word, where unrestricted sharing of data becomes an ultimate goal. This reflects the architecture of the software systems where the main focus is on building enterprise integrated solutions. Enterprise Integration Patterns (EIP) are used to architecture and design integrated solutions. During the past decades following integration styles have been identified: - file transfer - shared DB - RMI - messaging Asynchronous messaging is the most used architectural style for enterprise integration. It allows building of the loosely coupled solutions which overcomes limitations of the remote communication. This talk is about messaging, and the way Spring supports EIP via Spring Integration project.

1. ENTERPRISE INTEGRATION PATTERNS:
SPRING WAY
Dragan Gajic

2. INTEGRATION
• Creating a single, monolite app to cover
all aspects of business is hard
• Enterpises are comprised of
applications which can be: custom
build, 3rd party, legacy
• Connecting computer systems,
companies or people
• Share data and processes

3. INTEGRATION CHALLENGES
• Networks: unreliable & slow
• Differences: language, platform & data format
• Changes
• Limited control
• Standards
• Maintenance

4. INTEGRATION STYLES
• File transfer
• Shared DB
• RMI
• Messaging
• asyncronous
• reliable transfer
• common format (messages)
• Loose coupling

5. MESSAGE AND CHANNEL
• Message
• Header – information about the data
• Payload (body) – the data being transmitted
• Channel
Header
Payload
Header
Payload
• Point-to-Point
• Publish-Subscribe
Header
Payload
Header
Payload
Header
Payload
Producer Consumer

6. PIPES AND FILTERS
Persist
Pipe
Create validation
email
Pipe Pipe
Filter Filter
Send validation
email
SMTP
Pipe
Filter
USER
Registration
• Divide complex processing
• Filters – independent processing steps
• Pipes – connect filters into a sequence
• Fundamental architectural style for messaging
• Pipe = Channel
• Filter = Endpoint

7. SPRING INTEGRATION
• Top-level project in spring.io
• Enables lightweight messaging
• Combines DI, POJO and Messaging
• Implements most of EIP
• Includes wide selection of channel adapters
• SI != MOM, ESB

8. EXAMPLE: USER REGISTRATION
• After user registration validate email address by sending
confirmation link to email and notify moderators about new
profile
• In steps:
• Generate confirmation link (UUID)
• Store userId -> UUID
• Send confirmation email
• Notify site moderators about the new profile
SMTP
ADMIN
REST API

9. CHANNEL ADAPTER
@RequestMapping(method = RequestMethod.POST)
@ResponseStatus(HttpStatus.CREATED)
public ProfileResource register(@Valid @RequestBody RegistrationResource registration) {
Profile profile = profileService.save(regResToProfile.convert(registration));
publisher.publishEvent(new RegistrationEvent(this, profile));
return profileToProfileResource.convert(profile);
}
<int-event:inbound-channel-adapter channel="event-channel"
event-types=“x.x.RegistrationEvent"/>
<channel id="event-channel“ />

10. ENRICHER
<header-enricher input-channel="event-channel">
<header name="uuid“ expression="T(java.util.UUID).randomUUID.toString()"/>
</header-enricher>

11. WIRE-TAP
<wire-tap channel="logger"/>

12. PIPING IT ALL TOGETHER
<int-event:inbound-channel-adapter channel="event-channel"
event-types="com.levi9.samples.eip.registration.event.RegistrationEvent" />
<channel id="event-channel" />
<header-enricher input-channel="event-channel" output-channel=“logger">
<header name="uuid" expression="T(java.util.UUID).randomUUID().toString()" />
</header-enricher>
<logging-channel-adapter id="logger" level="INFO" log-full-message="true" />

13. COMPOSITE PROCESSOR

14. SPLITTER & ROUTER
<splitter input-channel="confirmation-channel“ output-channel="splitted" method="split">
<beans:bean class="com.levi9.samples.eip.registration.splitter.ProfileSplitter" />
</splitter>
<payload-type-router input-channel="splitted">
<mapping type="java.lang.Long" channel="save" />
<mapping type="com.levi9.samples.eip.registration.model.Profile" channel=“email" />
</payload-type-router>
public Object[] split(RegistrationEvent event) {
Profile profile = event.getProfile();
return new Object[] {profile.getId(), profile};
}

15. <service-activator input-channel="save" output-channel="done"
expression="@profileService.pending(headers.uuid, payload)" />
<chain input-channel="email" output-channel="done">
<int-mail:header-enricher>
<int-mail:from value="EIP" />
<int-mail:to expression="payload.email" />
<int-mail:subject value="Registration confirmation" />
</int-mail:header-enricher>
<transformer
expression="'Dear ' + payload.name + ', please click on the following link
#{ environment['host.name'] }/confirm/' + headers.uuid
+ ' in order to confirm email address.'" />
</chain>
SERVICE ACTIVATOR & TRANSLATOR
public boolean pending(String uuid, Long id) {
return confirmations.put(uuid, id) == null;
}

16. AGGREGATOR & MAIL ADAPTER
public String aggregate(List<Message<?>> messages) {
return (String) messages
.stream()
.filter(p -> p.getPayload() instanceof String)
.findFirst().orElse(null).getPayload();
}
<aggregator input-channel="done" method="aggregate" message-store=“store"
output-channel="mail-outbound" >
<bean class="com.levi9.samples.eip.registration.aggregator.ConfirmationAggregator"/>
</aggregator>
<channel id="mail-outbound" />
<int-mail:outbound-channel-adapter channel="mail-outbound"
host="#{ environment['mail.smtp.host']}"
port="#{ environment['mail.smtp.port']}" />
<bean id=“store" class="org.springframework.integration.store.SimpleMessageStore" />

17. MESSAGING SYSTEM
message
SMTP
ADMIN
REST API

18. DEMO
https://gitlab.levi9.com/d.gajic/eip/tree/code3

19. RESOURCES
• Book
• Enterprise Integration Patterns
• Gregor Hohpe, Bobby Woolf
• Spring Integration
• http://projects.spring.io/spring-integration
• Samples
• https://gitlab.levi9.com/d.gajic/eip.git
• Patterns
• http://www.enterpriseintegrationpatterns.com

20. Q&A