ENTERPRISE INTEGRATION PATTERNS: SPRING WAY Dragan Gajic 

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 

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

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

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

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 

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 

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 

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); }

ENRICHER 

WIRE-TAP 

PIPING IT ALL TOGETHER 

COMPOSITE PROCESSOR 

SPLITTER & ROUTER public Object[] split(RegistrationEvent event) { Profile profile = event.getProfile(); return new Object[] {profile.getId(), profile}; } 

SERVICE ACTIVATOR & TRANSLATOR public boolean pending(String uuid, Long id) { return confirmations.put(uuid, id) == null; } 

AGGREGATOR & MAIL ADAPTER public String aggregate(List> messages) { return (String) messages .stream() .filter(p -> p.getPayload() instanceof String) .findFirst().orElse(null).getPayload(); } 

MESSAGING SYSTEM message SMTP ADMIN REST API 

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

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 

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