Groovy & Grails for Spring/Java developers

Groovy & Grails for Java
developers
Peter Ledbrook, Developer Advocate
pledbrook@vmware.com / @pledbrook

© 2012 SpringOne 2GX. All rights reserved. Do not distribute without permission.

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• Grails for Swing applications
• MVC model http://griffon.codehaus.org/
• SwingBuilder for views

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)
}
}
}

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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

http://www.gradle.org/

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• Parallel processing for Groovy
• Actors library making full use of closures

@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!

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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What is Grails?

Grails
Servlet
Web MVC GSP (Views)
Container

GORM
Database I18n
(Data Access)

Build Test Support Doc Engine

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What is Grails?

Grails

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What is Grails?

Web Controllers
The Domain Model
i18n bundles
Business Logic
Custom View Tags
Views & Layouts
Libraries (JARs)
Build Commands
Additional Sources
Tests
Web Resources

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Say bye-bye to the plumbing!

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Enterprise requirements

Web App

Messaging JEE

Legacy
Services
Databases

Is this a problem for Grails apps?

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Build

• Remember the Grails project structure?
– add in build events and...

Can’t build natively with other build tools!

Ant Maven Gradle

Grails Build System

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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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Option 1: Custom ORM mapping

• No existing domain model
• Schema not too far off the beaten track

class Book {
...
static mapping = {
table "books"
title type: "books"
author column: "author_ref"
}
}

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Option 2: JPA annotations

• Existing Java/JPA domain model

<?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>

grails-app/conf/hibernate/hibernate.cfg.xml

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Option 3: Hibernate XML Mappings

• You have Java model + Hibernate mapping files
• Schema is way off the beaten track

<?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>

grails-app/conf/hibernate/hibernate.cfg.xml

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Constraints

Given domain class:

org.example.myapp.domain.Book

Then:

src/java/org/example/myapp/domain/BookConstraints.groovy

constraints = {
title blank: false, unique: true
...
}

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Option 4: GORM JPA Plugin

• GORM layer over JPA
• Use your own JPA provider
• Useful for cloud services that only work with JPA, not
Hibernate

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Database Migration Plugin

Pre-production, Hibernate ‘update’ or ‘create-drop’

dbm-generate-changelog
dbm-changelog-sync

Change domain model

dbm-gorm-diff
dbm-update

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Reverse Engineering Plugin

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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Groovy & Grails for Spring/Java developers

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