grails 3 inside and out

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Grails 3 Inside & OutBy Graeme Rocher

@graemerocher

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Who we are?

Jeff Scott Brown Object Computing Inc. @jeffscottbrown brownj@ociweb.com

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Graeme Rocher Object Computing Inc. @graemerocher rocherg@ociweb.com

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Grails + OCI• OCI focused on Grails• Full service support

– Consulting– Training– Support

• Commitment to engineering • Grails team at OCI growing

– Come speak to us!

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More at ociweb.com/grails

Visit the OCI’s Table #2 to meet our Grails Team!

Graeme Rocher Jeff Brown

Dave Klein Colin Harrington

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Agenda• Plugins & Traits• Plugins & Events• Configuration API• Code Generation API• Gradle & The Shell

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The Example• Build a Mail Sender Plugin

• Trait• Events• Configuration• Code Generation

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Plugins & Traits

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Adding Behaviour with Traits• Use Enhances to add behaviour

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importgrails.artefact.*

@Enhances('Controller')traitMyTrait{voidmyNewMethod(){…}}

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Core Grails Traits• Controller - implemented by all controllers• DomainClass - implemented by all domain classes

• GormEntity - implemented by all GORM entities• Service - implemented by all services• TagLibrary - implemented by all tag libraries• Interceptor - all Grails interceptors• Events - Any object that wants to send events

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Events

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Events• Any class that implements the Events trait can send and receive events• Controllers and services implement the trait by default• You can effectively decouple systems using an event driven approach• Fits nicely with reactive programming• Events are built on the Reactor framework

• http://projectreactor.io

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Events• Use on to listen and notify to send or combine with sendAndReceive

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notify('mail:sent',eventFor(message))

on('mail:sent'){Event<TYPE>event->//dostuff}

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Events• The Consumer and Selector annotations from Spring Reactor work too!

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@ConsumerclassMyService{

@Selector('mail:sent')voidmailEventListener(MailMessagemsg){//dostuff}}

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Configuration API

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Configuration API

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booleanisFooEnabled=config.getProperty('foo.bar',Boolean,true)

//or

@Value('foo.bar')booleanisFooEnabled

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Plugins & Configuration• Applications inherit plugin configuration• You should keep your plugin configuration minimal• Plugin configuration defines the default values• Applications can override any plugin provided value

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Code Generation & Grails

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Code Generation Scripts• Go in src/main/scripts in plugins or applications• All scripts subclass the GroovyScriptCommand class• Some handy properties

• gradle - for invoking Gradle• ant - for invoking Ant• methodMissing - for invoking other code gen commands

• Useful traits• TemplateRenderer - for rendering templates• FileSystemInteraction - for interacting with the file system

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Code Generation Scripts• The model method exposes a Model interface for introspecting conventions

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interfaceModel{StringgetClassName()StringgetFullName()StringgetPackageName()…StringgetLowerCaseName()Stringconvention(StringconventionName)Map<String,Object>asMap()}

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DSL for Code Generation Scripts

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description("Createsaservicethatsendsamail"){usage"Thisdoescoolsstuff"}

defmodel=model(args[0])

rendertemplate:template('MailService.groovy'),destination:file("grails-app/services/${model.packagePath}/${model.convention('Service')}.groovy"),model:model

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Gradle & The Shell

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Gradle & The Shell• Create Gradle tasks that invoke your app

• Without knowing any Gradle! ;-)

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classMailBatcherCommandimplementsApplicationCommand{booleanhandle(ExecutionContextcontext){//DOSTUFFreturntrue}}

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Gradle & The Shell• Just add to build.gradle build class path and run the command

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classpath'org.grails.plugins:mailSender:0.1-SNAPSHOT'

gradlebatchSendMailgrailsbatch-send-mail

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Summary• Grails 3 provides powerful techniques to build plugins that empower your

application• The core philosophy of plugins and modular applications continues• Through traits and events Grails 3 is more powerful that ever before!• Grails’ internals are all based on the described techniques

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Q & A

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More at ociweb.com/grails

The OCI Grails Team is growing — will You join us?

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Stay Connected.

Web: grails.orgStackOverflow: http://stackoverflow.com/tags/grails Slack: http://slack-signup.grails.org Twitter: twitter.com/grailsframeworkLinkedIn: http://linkedin.com/groups/Grails-User-Group-39757

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