groovy & grails for spring/java developers
Post on 10-May-2015
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Groovy & Grails for Java developers
Peter Ledbrook, Developer Advocatepledbrook@vmware.com / @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: pledbrook@vmware.com• t: pledbrook• b: http://blog.springsource.com/author/peter-ledbrook/
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Q&A
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