groovy & grails for spring/java developers
DESCRIPTION
Presentation given at SpringOne 2GX. The original presentation is mostly demo, but these slides show some nice features of Groovy and how Grails can support the varying needs to enterprise developers.TRANSCRIPT
Groovy & Grails for Java developers
Peter Ledbrook, Developer [email protected] / @pledbrook
© 2012 SpringOne 2GX. All rights reserved. Do not distribute without permission.
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Demo
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• Grails for Swing applications• MVC model• SwingBuilder for views
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application(title: 'DemoConsole', pack: true, locationByPlatform: true) { panel(border: emptyBorder(6)) { borderLayout() scrollPane(constraints: CENTER) { textArea( text: bind(target: model, targetProperty: 'scriptSource'), enabled: bind {model.enabled}, columns: 40, rows: 10) } }}
http://griffon.codehaus.org/
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Gradle
• Build tool with built-in dependency management• Conventions through plugins• Multi-project support• Full access to tasks and dependency tree• Easy to write your own tasks
– either in the build file– or via Groovy/Java classes
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http://www.gradle.org/
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• Parallel processing for Groovy• Actors library making full use of closures
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@Grab(group='org.codehaus.gpars', module='gpars', version='0.11')import groovyx.gpars.GParsPool
GParsPool.withPool { def animals = ['dog', 'ant', 'cat', 'whale'] println(animals.anyParallel {it ==~ /ant/} ? 'Found an ant' : 'No ants found') println(animals.everyParallel {it.contains('a')} ? 'All animals contain a' : 'Some animals can live without an a')}
http://gpars.codehaus.org/
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Try it out!
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http://groovyconsole.appspot.com/
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What is Grails?
• Rapid Web Application Development Framework– for the JVM– with first-class Java integration
• Inspired by Ruby on Rails, Django and others– Convention over Configuration– Don’t Repeat Yourself (DRY)
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Grails
What is Grails?
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Build
Web MVC GSP (Views)
GORM(Data Access)
Doc Engine
Servlet Container
Test Support
Database I18n
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Grails
What is Grails?
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What is Grails?
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Web ControllersThe Domain Model
Business Logic
Custom View TagsViews & Layouts
Libraries (JARs)
Additional Sources
Web Resources
i18n bundles
Build Commands
Tests
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Say bye-bye to the plumbing!
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Demo
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Enterprise requirements
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Web App
Messaging
Legacy Databases Services
JEE
Is this a problem for Grails apps?
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Build
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• Remember the Grails project structure?– add in build events and...
Can’t build natively with other build tools!
Grails Build System
Ant GradleMaven
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Dependency DSL
grails.project.dependency.resolution = { inherits "global" log "warn" repositories { grailsHome() mavenCentral() mavenRepo "http://localhost:8081/..." } ...}
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Dependency DSL
grails.project.dependency.resolution = { inherits "global" log "warn" ... dependencies { runtime "mysql:mysql-connector-java:5.1.17" test "org.gmock:gmock:0.8.1" ... } plugins { compile ":spring-security-core:1.2.7" ... }}
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‘Legacy’ Databases
• Grails can create a database from your domain model...• ...but what if you don’t own the database?
– DBA determines structure– Company conventions– Existing ‘legacy’ database
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• No existing domain model• Schema not too far off the beaten track
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Option 1: Custom ORM mapping
class Book { ... static mapping = { table "books" title type: "books" author column: "author_ref" }}
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• Existing Java/JPA domain model
Option 2: JPA annotations
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grails-app/conf/hibernate/hibernate.cfg.xml
<?xml version='1.0' encoding='UTF-8'?><!DOCTYPE ...><hibernate-configuration> <session-factory> <mapping class="org.ex.Book"/> <mapping class="org.ex.Author"/> ... </session-factory></hibernate-configuration>
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• You have Java model + Hibernate mapping files• Schema is way off the beaten track
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grails-app/conf/hibernate/hibernate.cfg.xml
Option 3: Hibernate XML Mappings
<?xml version='1.0' encoding='UTF-8'?><!DOCTYPE ...><hibernate-configuration> <session-factory> <mapping resource="org.ex.Book.hbm.xml"/> <mapping resource="org.ex.Author.hbm.xml"/> ... </session-factory></hibernate-configuration>
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constraints = { title blank: false, unique: true ...}
Constraints
Given domain class:
Then:
org.example.myapp.domain.Book
src/java/org/example/myapp/domain/BookConstraints.groovy
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• GORM layer over JPA• Use your own JPA provider• Useful for cloud services that only work with JPA, not
Hibernate
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Option 4: GORM JPA Plugin
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Database Migration Plugin
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Pre-production, Hibernate ‘update’ or ‘create-drop’
dbm-generate-changelogdbm-changelog-sync
Change domain model
dbm-gorm-diffdbm-update
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Reverse Engineering Plugin
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class Person { String name Integer age ...}
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Grails is Spring
• Spring MVC under the hood• Grails provides many useful beans
– e.g. grailsApplication• Define your own beans!
– resources.xml/groovy– In a plugin
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Example
import ...beans = { credentialMatcher(Sha1CredentialsMatcher) { storedCredentialsHexEncoded = true }
sessionFactory(ConfigurableLocalSessionFactoryBean) { dataSource = ref("dataSource") hibernateProperties = [ "hibernate.hbm2ddl.auto": "create-drop", "hibernate.show_sql": true ] }}
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Summary
• Various options for integrating Grails with:– Development/build– Deployment processes
• Works with many external systems– Solid support for non-Grailsy DB schemas– Flexible messaging & web service support
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More info
• w: http://grails.org/• f: http://grails.org/Mailing+Lists
• e: [email protected]• t: pledbrook• b: http://blog.springsource.com/author/peter-ledbrook/
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Q&A
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