This document summarizes various AST transformations in Groovy including local transformations used in Groovy, Grails, and Griffon as well as examples of annotations like @Singleton, @Delegate, @Immutable, @Category, @Mixin, @Grab, @Log, @InheritConstructors, @Canonical, @Scalify, @Entity, @Bindable, @Listener, @EventPublisher, @Scaffold. It also provides a recipe for implementing custom AST transformations with an interface, transformation class, and annotation. Finally it mentions other types of transformations like GContracts, Spock, CodeNarc, and Griffon.

1. Groovy
AST

3. Agenda
• Local
ASTTransforma5ons
– Groovy
– Grails
– Griffon
• Como
funcionan?
• Otras
formas
de
modificar
AST

4. LISTADO
DE
TRANSFORMACIONES
DE
AST
(NO
EXHAUSTIVO)

5. @Singleton
@Singleton
class AccountManager {
void process(Account account) { ... }
}
def account = new Account()
AccountManager.instance.process(account)

6. @Delegate
class Event {
@Delegate Date when
String title, url
}
df = new SimpleDateFormat("MM/dd/yyyy")
so2gx = new Event(title: "SpringOne2GX",
url: "http://springone2gx.com",
when: df.parse("10/19/2010"))
oredev = new Event(title: "Oredev",
url: "http://oredev.org",
when: df.parse("11/02/2010"))
assert oredev.after(so2gx.when)

7. @Immutable
@Immutable
class Person {
String name
}
def person1 = new Person("ABC")
def person2 = new Person(name: "ABC")
assert person1 == person2
person1.name = "Boom!” // error!

8. @Category
@Category(Integer)
class Pouncer {
String pounce() {
(1..this).collect([]) {
'boing!' }.join(' ')
}
}
use(Pouncer) {
3.pounce() // boing! boing! boing!
}

9. @Mixin
class Pouncer {
String pounce() {
(1..this.times).collect([]) {
'boing!' }.join(' ')
}
}
@Mixin(Pouncer)
class Person{
int times
}
person1 = new Person(times: 2)
person1.pounce() // boing! boing!

10. @Grab
@Grab('net.sf.json-lib:json-lib:2.3:jdk15')
def builder = new
net.sf.json.groovy.JsonGroovyBuilder()
def books = builder.books {
book(title: "Groovy in Action",
name: "Dierk Koenig")
}
assert books.name == ["Dierk Koenig"]

11. @Log
@groovy.util.logging.Log
class Person {
String name
void talk() {
log.info("$name is talking…")
}
}
def person = new Person(name: "Duke")
person.talk()
// Oct 7, 2010 10:36:09 PM sun.reflect.NativeMethodAccessorImpl invoke0
// INFO: Duke is talking…

12. @InheritConstructors
@groovy.transform.InheritConstructors
class MyException extends RuntimeException {}
def x1 = new MyException("Error message")
def x2 = new MyException(x1)
assert x2.cause == x1

13. @Canonical
@groovy.transform.Canonical
class Person {
String name
}
def person1 = new Person("Duke")
def person2 = new Person(name: "Duke")
assert person1 == person2
person2.name = "Tux"
assert person1 != person2

14. @Scalify
trait Output {
@scala.reflect.BeanProperty
var output:String = ""
}
@groovyx.transform.Scalify
class GroovyOutput implements Output {
String output
}

15. @En5ty
@grails.persistence.Entity
class Book {
String title
}
def book = new Book().save()
assert book.id
assert book.version

16. @Bindable
@groovy.beans.Bindable
class Book {
String title
}
def book = new Book()
book.addPropertyChangeListener({e ->
println "$e.propertyName $e.oldValue ->
$e.newValue"
} as java.beans.PropertyChangeListener)
book.title = "Foo” // prints "title Foo"
book.title = "Bar” // prints "title Foo Bar"

17. @Listener
@groovy.beans.Bindable
class Book {
@griffon.beans.Listener(snooper)
String title
private snooper = {e ->
println "$e.propertyName $e.oldValue ->
$e.newValue"
}
}
def book = new Book()
book.title = "Foo" // prints "title Foo"
book.title = "Bar" // prints "title Foo Bar"

18. @EventPublisher
@Singleton
@griffon.util.EventPublisher
class AccountManager {
void process(Account account) {
publishEvent("AccountProcessed", [account)]
}
}
def am = AccountManager.instance
am.addEventListener("AccountProcessed") { account ->
println "Processed account $account"
}
def acc = new Account()
AccountManager.instance.process(acc)
// prints "Processed account Account:1"

19. @Scaffold
class Book {
String title
}
@griffon.presentation.Scaffold
class BookBeanModel {}
def model = new BookBeanModel()
def book = new Book(title: "Foo")
model.value = book
assert book.title == model.title.value
model.value = null
assert !model.title.value
assert model.title

20. @En5ty
@griffon.persistence.Entity(‘gsql’)
class Book {
String title
}
def book = new Book().save()
assert book.id
assert book.version

21. Y
otras
tantas
…
• @PackageScope
• @Lazy
• @Newify
• @Field
• @Synchronized
• @Vetoable
• @ToString,
@EqualsAndHashCode,
@TupleConstructor
• @AutoClone,
@AutoExternalize
• …

22. LA
RECETA
SECRETA
PARA
HACER
TRANSFORMACIONES
DE
AST

23. 1
Definir
interface
@Retention(RetentionPolicy.SOURCE)
@Target({ElementType.FIELD, ElementType.TYPE})
@GroovyASTTransformationClass
("org.codehaus.griffon.ast.ListenerASTTransformation
")
public @interface Listener {
String value();
}

24. 2
Implementar
la
transformacion
import org.codehaus.groovy.control.CompilePhase;
import org.codehaus.groovy.transform.ASTTransformation;
import org.codehaus.groovy.transform.GroovyASTTransformation;
@GroovyASTTransformation(phase=CompilationPhase.CANONICALIZATION)
public class ListenerASTTransformation
implements ASTTransformation {
public void visit(ASTNode[] nodes, SourceUnit source) {
// MAGIC GOES HERE, REALLY! =)
}
}

25. 3
Anotar
el
codigo
@groovy.beans.Bindable
class Book {
@griffon.beans.Listener(snooper)
String title
private snooper = {e ->
// awesome code …
}
}

26. OTRO
TIPO
DE
TRANSFORMACIONES

27. GContracts

28. Spock

29. CodeNarc

30. Griffon

31. Gracias!
@aalmiray
hXp://jroller.com/aalmiray