Groovy & Grails for Java Developers

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Groovy and Grails for Java developers Peter Ledbrook SpringSource t: @pledbrook g: +PeterLedbrook e: pledbrook@vmware.com

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What is Groovy? • A dynamic language for the JVM – ...with a Java-like syntax – ...and optional static types • Uses and extends the JDK • Write scripts as well as classes • Seamless integration with Java – ...call Java from Groovy – ...or call Groovy from Java – ...all in the same project • Great IDE support in IntelliJ and Eclipse – NetBeans also has Groovy (& Grails support)

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3 GroovyBean syntax

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4 Deﬁne properties as ﬁelds...

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5 ...and initialize them on construction

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6 Deﬁne a getter method...

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7 ...and still use property syntax to access it

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9 Properties implicitly have getter and setter methods

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11 Use the @Immutable annotation...

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12 ...and typed properties...

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13 ...to get a standard constructor...

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14 ...and make instances immutable

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17 Use single or double-quotes for strings

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18 Double quotes allow for embedded expressions

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19 Use array syntax to access characters of a string

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21 Array syntax with ranges extracts substrings

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22 and can even allow for reversing of the substring

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23 Triple quotes for multi-line strings

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25 Java doubles are not exact

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27 Java solution with BigDecimal is ugly

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28 Groovy uses BigDecimal by default and provides operator support

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29 for precise ﬂoating-point calculations

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31 List literals

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32 Extra collection methods for convenience

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34 Easy map iteration with key and value as separate arguments

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36 Collection ﬁltering with closures

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38 Map one collection to another by applying a function to each element

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39 Same collection, but each element has a value of 3 less than before

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41 Slashy string literals for use with regular expressions

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42 Backslash in regex does not need escaping

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43 Iterate over matches...

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44 ...and use array syntax to access the match groups

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45 Literal for compiled patterns

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46 Generate XML from Groovy code

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47 Methods with closures become nested elements

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49 Named arguments become attributes

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51 Because it’s Groovy code, use conditions and loops

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53 Easy XML parsing

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54 Parse and create a DOM-like object

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55 And use properties, array-syntax, etc. to access elements and content

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58 ‘@’-syntax for accessing attributes

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60 Even incorporate ﬁltering

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Where to use Groovy • Scripts – especially with groovyserv – cross-platform • Tests – syntax more expressive – Spock for BDD • Java application plugins/scripting – GroovyShell – GroovyClassLoader • Domain Specific Languages • Higher-level application development

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Scripting with SQL 62

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Scripting with SQL 63 Create a new Sql instance with JDBC connection details

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Scripting with SQL 64 Easy querying and processing or results

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Scripting with SQL 65 Easy, safe updates with GStrings

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66 Scripting with XML content

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67 Scripting with XML content Grab content from URLs with automatic closing of the stream

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68 Scripting with XML content Then hook into other Groovy features for processing the content

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69 Scripting with XML content Easy writing to ﬁles, with safe ﬁle stream close

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70 Scripting with XML content Print to the new ﬁle

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71 Scripting with XML content Iteration over elements in the XML

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Scripting with GORM 72

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Scripting with GORM 73 Use @Grab to include external dependencies

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Scripting with GORM 74 Deﬁne a domain class...

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Scripting with GORM 75 ...and use GORM/MongoDB to save data

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Spock • BDD testing framework • Encourages simple test structure • ...and documented tests • given...when...then • + data-driven tests! • Can run via JUnit test runner 76 http://code.google.com/p/spock/ http://meetspock.appspot.com/

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77 Using Spock

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Implementing a DSL 78

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Groovy in Maven 79

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Groovy in Maven 80

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Groovy in Maven 81

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• Grails for Swing applications • MVC model • SwingBuilder for views 82 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 83 http://www.gradle.org/

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• Parallel processing for Groovy • Actors library making full use of closures 84 @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! 85 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) 86

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Grails What is Grails? 87 Build Web MVC GSP (Views) GORM (Data Access) Doc Engine Servlet Container Test Support Database I18n

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Grails What is Grails? 88

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What is Grails? 89 Web Controllers The Domain Model Business Logic Custom View Tags Views & Layouts Libraries (JARs) Additional Sources Web Resources i18n bundles Build Commands Tests

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Say bye-bye to the plumbing! 90

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Demo

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Enterprise requirements 92 Web App Messaging Legacy Databases Services JEE Is this a problem for Grails apps?

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Build 93 • Remember the Grails project structure? – add in build events and... Can’t build natively with other build tools! Grails Build System Ant Gradle Maven

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Dependency DSL grails.project.dependency.resolution = { inherits "global" log "warn" repositories { grailsHome() mavenCentral() mavenRepo "http://localhost:8081/..." } ... } 94

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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" ... } } 95

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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 96

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• No existing domain model • Schema not too far off the beaten track 97 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 98 grails-app/conf/hibernate/hibernate.cfg.xml ...

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• You have Java model + Hibernate mapping files • Schema is way off the beaten track 99 grails-app/conf/hibernate/hibernate.cfg.xml Option 3: Hibernate XML Mappings ...

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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 100

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• GORM layer over JPA • Use your own JPA provider • Useful for cloud services that only work with JPA, not Hibernate 101 Option 4: GORM JPA Plugin

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Database Migration Plugin 102 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 103 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 104

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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 ] } } 105

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Enterprise Integration • Spring opens up a world of possibilities – Spring Integration/Camel – Messaging (JMS/AMQP) – ESB – RMI, HttpInvoker, etc. • Web services & REST 106

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Grails Plugins • Routing • JMS, RabbitMQ • CXF, Spring-WS, WS-Client • REST 107

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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 108

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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/ 109

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Q&A