Groovy & Grails for Java Developers

Groovy is a dynamic language for the JVM with a Java-like syntax, and Grails is a rapid web application framework that uses the language extensively.

Find out how Groovy can improve a Java developer's life and what jobs it's really good for. Also learn about Grails and how it provides more than just a CRUD web framework, with strong enterprise integration features.

Transcript

1. Groovy and Grails for Java developers Peter Ledbrook SpringSource t: @pledbrook g: +PeterLedbrook e: pledbrook@vmware.com
2. 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)
3. 3 GroovyBean syntax
4. 4 Define properties as fields...
5. 5 ...and initialize them on construction
6. 6 Define a getter method...
7. 7 ...and still use property syntax to access it
9. 9 Properties implicitly have getter and setter methods
11. 11 Use the @Immutable annotation...
12. 12 ...and typed properties...
13. 13 ...to get a standard constructor...
14. 14 ...and make instances immutable
17. 17 Use single or double-quotes for strings
18. 18 Double quotes allow for embedded expressions
19. 19 Use array syntax to access characters of a string
21. 21 Array syntax with ranges extracts substrings
22. 22 and can even allow for reversing of the substring
23. 23 Triple quotes for multi-line strings
25. 25 Java doubles are not exact
27. 27 Java solution with BigDecimal is ugly
28. 28 Groovy uses BigDecimal by default and provides operator support
29. 29 for precise floating-point calculations
31. 31 List literals
32. 32 Extra collection methods for convenience
34. 34 Easy map iteration with key and value as separate arguments
36. 36 Collection filtering with closures
38. 38 Map one collection to another by applying a function to each element
39. 39 Same collection, but each element has a value of 3 less than before
41. 41 Slashy string literals for use with regular expressions
42. 42 Backslash in regex does not need escaping
43. 43 Iterate over matches...
44. 44 ...and use array syntax to access the match groups
45. 45 Literal for compiled patterns
46. 46 Generate XML from Groovy code
47. 47 Methods with closures become nested elements
49. 49 Named arguments become attributes
51. 51 Because it’s Groovy code, use conditions and loops
53. 53 Easy XML parsing
54. 54 Parse and create a DOM-like object
55. 55 And use properties, array-syntax, etc. to access elements and content
58. 58 ‘@’-syntax for accessing attributes
60. 60 Even incorporate filtering
61. 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
62. Scripting with SQL 62
63. Scripting with SQL 63 Create a new Sql instance with JDBC connection details
64. Scripting with SQL 64 Easy querying and processing or results
65. Scripting with SQL 65 Easy, safe updates with GStrings
66. 66 Scripting with XML content
67. 67 Scripting with XML content Grab content from URLs with automatic closing of the stream
68. 68 Scripting with XML content Then hook into other Groovy features for processing the content
69. 69 Scripting with XML content Easy writing to files, with safe file stream close
70. 70 Scripting with XML content Print to the new file
71. 71 Scripting with XML content Iteration over elements in the XML
72. Scripting with GORM 72
73. Scripting with GORM 73 Use @Grab to include external dependencies
74. Scripting with GORM 74 Define a domain class...
75. Scripting with GORM 75 ...and use GORM/MongoDB to save data
76. 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/
77. 77 Using Spock
78. Implementing a DSL 78
79. Groovy in Maven 79
80. Groovy in Maven 80
81. Groovy in Maven 81
82. • 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/
83. 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/
84. • 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/
85. Try it out! 85 http://groovyconsole.appspot.com/
86. 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
87. Grails What is Grails? 87 Build Web MVC GSP (Views) GORM (Data Access) Doc Engine Servlet Container Test Support Database I18n
88. Grails What is Grails? 88
89. 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
90. Say bye-bye to the plumbing! 90
91. Demo
92. Enterprise requirements 92 Web App Messaging Legacy Databases Services JEE Is this a problem for Grails apps?
93. 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
94. Dependency DSL grails.project.dependency.resolution = { inherits "global" log "warn" repositories { grailsHome() mavenCentral() mavenRepo "http://localhost:8081/..." } ... } 94
95. 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
96. ‘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
97. • 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" } }
98. • Existing Java/JPA domain model Option 2: JPA annotations 98 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>
99. • 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 <?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>
100. 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
101. • 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
102. 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
103. Reverse Engineering Plugin 103 class Person { String name Integer age ... }
104. 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
105. Example import ... beans = { credentialMatcher(Sha1CredentialsMatcher) { storedCredentialsHexEncoded = true } sessionFactory(ConfigurableLocalSessionFactoryBean) { dataSource = ref("dataSource") hibernateProperties = [ "hibernate.hbm2ddl.auto": "create-drop", "hibernate.show_sql": true ] } } 105
106. Enterprise Integration • Spring opens up a world of possibilities – Spring Integration/Camel – Messaging (JMS/AMQP) – ESB – RMI, HttpInvoker, etc. • Web services & REST 106
107. Grails Plugins • Routing • JMS, RabbitMQ • CXF, Spring-WS, WS-Client • REST 107
108. 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
109. 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
110. Q&A