What's new in Apache Groovy 2.4, 2.5, 3.0....

Sinon quoi de neuf
côté Apache Groovy?
Guillaume Laforge 
@glaforge
 
PMC Chair of  
Apache Groovy  
 
Developer Advocate  
Google Cloud Platform
Cédric Champeau 
@cedricchampeau
 
PMC Member of  
Apache Groovy  
 
Principal Engineer
Gradle Inc.

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2
@Canonical becomes a meta-annotation
import groovy.transform.* 
 
@Canonical(includeNames = true) 
class Person { 
String name 
int age 
} 
 
assert new Person('Guillaume', 39).toString() == 
'Person(name:Guillaume, age:39)'

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2
@Canonical becomes a meta-annotation
 
@Canonical(includeNames = true) 
class Person { 
String name 
int age 
} 
 
assert new Person('Guillaume', 39).toString() == 
'Person(name:Guillaume, age:39)'
includeNames
from @ToString

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3
More control on annotation collector
DUPLICATE
Annotations from the annotation
collection will always be inserted.
PREFER_COLLECTOR
Annotations from the collector will be
added and any existing annotations
with the same name will be removed.
PREFER_EXPLICIT
ignored if any existing annotations with
the same name are found.
PREFER_EXPLICIT_MERGED
ignored if any existing annotations with
the same name are found but any new
parameters on the collector annotation
will be added to existing annotations.
PREFER_COLLECTOR_MERGED
added and any existing annotations
with the same name will be removed
but any new parameters found within
existing annotations will be merged
into the added annotation.

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4
Pre/post events for @TupleConstructor
import groovy.transform.TupleConstructor
@TupleConstructor(pre = { first = first?.toLowerCase() })
class Person {
String first
}
def p = new Person('Jack')
assert p.first == 'jack'

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4
Pre/post events for @TupleConstructor
@TupleConstructor(pre = { first = first?.toLowerCase() })
class Person {
String first
}
assert p.first == 'jack'
import static groovy.test.GroovyAssert.shouldFail
@TupleConstructor(pre = { assert first })
class Person {
String first
}
shouldFail {
def unknown = new Person()
}

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5
Prevent @TupleConstructor default ctors
@TupleConstructor 
class Person { 
String first, last 
int age 
}

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5
class Person { 
int age 
}
Generates:
Person(String first, String last, int age) { /*...*/ }
Person(String first, String last) { this(first, last, 0) }
Person(String first) { this(first, null) }
Person() { this(null) }

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6
@TupleConstructor(defaults = true) 
class Person {
int age 
}

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6
@TupleConstructor(defaults = true) 
class Person {
int age 
}
Generates only:
Person(String ﬁrst, String last, int age) { /*...*/ }

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7
New @MapConstructor transformation
 
class Person { 
} 
 
@CompileStatic // optional 
@ToString(includeSuperProperties = true) 
@MapConstructor(pre = { super(args?.first, args?.last); 
args = args ?: [:] }, 
post = { first = first?.toUpperCase() }) 
class Author extends Person { 
String bookName 
}
assert new Author(first: 'Dierk',
last: 'Koenig',
bookName: 'ReGinA').toString() ==
'Author(ReGinA, DIERK, Koenig)' 
 
assert new Author().toString() ==
'Author(null, null, null)'

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7
New @MapConstructor transformation
 
class Person { 
} 
 
@CompileStatic // optional 
@ToString(includeSuperProperties = true) 
@MapConstructor(pre = { super(args?.first, args?.last); 
args = args ?: [:] }, 
post = { first = first?.toUpperCase() }) 
class Author extends Person { 
String bookName 
}
assert new Author(first: 'Dierk',
last: 'Koenig',
bookName: 'ReGinA').toString() ==
'Author(ReGinA, DIERK, Koenig)' 
 
assert new Author().toString() ==
'Author(null, null, null)'
Can decorate map
ctor with pre / post-
instructions

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8
Properties validated in AST xforms
import groovy.transform.AutoClone 
 
@AutoClone(excludes = 'sirName') 
class Person { 
String firstName 
String surName 
} 
 
new Person(firstName: "John",
surName: "Doe").clone()

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8
Properties validated in AST xforms
import groovy.transform.AutoClone 
 
@AutoClone(excludes = 'sirName') 
class Person { 
String firstName 
String surName 
} 
 
new Person(firstName: "John",
surName: "Doe").clone()
Error during @AutoClone
processing: 'excludes'
property 'sirName'
does not exist.

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9
@Immutable support in class hierarchy
 
@EqualsAndHashCode 
class Person { 
String name 
}

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9
 
class Person { 
String name 
}
@Immutable 
@TupleConstructor(includeSuperProperties = true) 
@EqualsAndHashCode(callSuper = true) 
@ToString(includeNames = true, includeSuperProperties = true) 
class Athlete extends Person { 
String sport 
}

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9
 
class Person { 
String name 
}
@Immutable 
@TupleConstructor(includeSuperProperties = true) 
@EqualsAndHashCode(callSuper = true) 
@ToString(includeNames = true, includeSuperProperties = true) 
class Athlete extends Person { 
String sport 
}
def d1 = new Athlete('Michael Jordan', 'BasketBall') 
def d2 = new Athlete(name: 'Roger Federer', sport: 'Tennis')
assert d1 != d2 
assert d1.toString() ==  
'Athlete(sport:BasketBall, name:Michael Jordan)' 
assert d2.toString() ==  
'Athlete(sport:Tennis, name:Roger Federer)'

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10
@Immutable supports Optional
import groovy.transform.Immutable 
 
@Immutable 
class Person { 
String name 
Optional address 
} 
 
def p = new Person('Joe', Optional.of('Home')) 
 
assert p.toString() == 'Person(Joe, Optional[Home])' 
assert p.address.get() == 'Home'

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10
@Immutable supports Optional
import groovy.transform.Immutable 
 
@Immutable 
class Person { 
String name 
Optional address 
} 
 
def p = new Person('Joe', Optional.of('Home')) 
 
assert p.toString() == 'Person(Joe, Optional[Home])' 
assert p.address.get() == 'Home'
@Immutable 
class Person { 
String name 
Optional birth 
}
Fails compilation,
as Date is mutable

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11
New @AutoImplement transformation
@AutoImplement 
class MyNames extends AbstractList implements Closeable {}

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11
@AutoImplement 
class MyNames extends AbstractList implements Closeable {}
class MyNames extends AbstractList implements Closeable { 
String get(int param0) { 
return null 
} 
boolean addAll(Collection extends String> param0) { 
return false 
} 
void close() throws Exception { 
} 
int size() { 
return 0 
} 
}

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12
@AutoImplement(exception = IOException) 
class MyWriter extends Writer { }

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12
@AutoImplement(exception = UnsupportedOperationException, 
message = 'Not supported by MyIterator') 
class MyIterator implements Iterator { }

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12
@AutoImplement(exception = UnsupportedOperationException, 
message = 'Not supported by MyIterator') 
class MyIterator implements Iterator { }
@AutoImplement(code = { throw new UnsupportedOperationException( 
'Should never be called but was called on ' + new Date()) }) 
class EmptyIterator implements Iterator { 
boolean hasNext() { false } 
}

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13
:grab command in groovysh
groovy:000> :grab 'com.google.guava:guava:19.0'
groovy:000> import com.google.common.collect.BiMap
===> com.google.common.collect.BiMap

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14
@Delegate on getters too
class Person { 
String name
@Delegate 
String getName() {
name.reverse()
}
}
def p = new Person(name: 'Erine')
assert p.toUpperCase() == 'ENIRE'

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15
JAXB marshalling shortcuts
import groovy.transform.EqualsAndHashCode
import javax.xml.bind.JAXBContext
import javax.xml.bind.annotation.*
@EqualsAndHashCode
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement
class Person {
String name
int age
}

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15
@EqualsAndHashCode
@XmlRootElement
class Person {
String name
int age
}
def jaxbContext =
JAXBContext.newInstance(Person)
def p = new Person(name: 'Marion', age: 9)
def xml = jaxbContext.marshal(p)
assert jaxbContext.unmarshal(xml, Person) == p

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15
@EqualsAndHashCode
@XmlRootElement
class Person {
String name
int age
}
def jaxbContext =
JAXBContext.newInstance(Person)
def p = new Person(name: 'Marion', age: 9)
def xml = jaxbContext.marshal(p)
assert jaxbContext.unmarshal(xml, Person) == p
No need for
createMarshaller()

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16
CliBuilder supports annotations
// specify parameters 
def cli = new CliBuilder(usage: 'groovy Greeter [option]') 
cli.a(longOpt: 'audience', args: 1, 'greeting audience') 
cli.h(longOpt: 'help', 'display usage') 
 
// parse and process parameters 
def options = cli.parse(args) 
if (options.h) cli.usage() 
else println "Hello ${options.a ? options.a : 'World'}"

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17
import groovy.cli.* 
 
interface GreeterI { 
@Option(shortName='h', description='display usage')
Boolean help() 
@Option(shortName='a', description='greeting audience')
String audience() 
@Unparsed
List remaining() 
}

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17
import groovy.cli.* 
 
interface GreeterI { 
@Option(shortName='h', description='display usage')
Boolean help() 
@Option(shortName='a', description='greeting audience')
String audience() 
@Unparsed
List remaining() 
}
def cli = new CliBuilder(usage: 'groovy Greeter [option]') 
def argz = '--audience Groovologist'.split() 
def options = cli.parseFromSpec(GreeterI, argz) 
assert options.audience() == 'Groovologist'

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18
With… tap…
@Canonical 
class Person { 
String name 
int age 
}

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18
With… tap…
assert new Person().with {
name = 'Guillaume'
age = 39
return it
}.toString() == 'Person(Guillaume, 39)'
@Canonical 
class Person { 
String name 
int age 
}

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18
With… tap…
assert new Person().with {
name = 'Guillaume'
age = 39
return it
assert new Person().tap {
name = 'Guillaume'
age = 39
@Canonical 
class Person { 
String name 
int age 
}

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19
Miscellaneous
• Map#retainAll {} and Map#removeAll {} methods
• GDK’s createSimilarCollection() and
createSimilarMap() methods support all the JDK’s
collections and maps
• New File#relativePath(file) method

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JSON
generator

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21
A customizable JSON serializer
class Person { 
String name 
String title 
int age 
String password 
Date dob 
URL favoriteUrl 
}
Person person = new Person(name: 'John', title: null,  
age: 21, password: 'secret', 
dob: Date.parse('yyyy-MM-dd', '1984-12-15'), 
favoriteUrl: new URL('http://groovy-lang.org/')) 
 
def generator = new JsonGenerator.Options() 
.excludeNulls() 
.dateFormat('[email protected]') 
.excludeFieldsByName('age', 'password') 
.excludeFieldsByType(URL) 
.build() 
 
assert generator.toJson(person) ==  
'{"dob":"[email protected]","name":"John"}'

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22
.addConverter(URL) { URL u, String key -> 
if (key == 'favoriteUrl') { 
u.getHost() 
} else { 
u 
} 
} 
.build()

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22
u.getHost() 
} else { 
u 
} 
} 
.build()
Data type to
customize

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22
u.getHost() 
} else { 
u 
} 
} 
.build()
Data type to
customize
Optional key

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AST
macros

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24
AST macros: the old way
@Retention(RetentionPolicy.SOURCE) 
@Target([ElementType.TYPE]) 
@GroovyASTTransformationClass([
"metaprogramming.AddMethodASTTransformation"])
@interface AddMethod { }

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24
@Target([ElementType.TYPE]) 
"metaprogramming.AddMethodASTTransformation"])
@interface AddMethod { }
Let’s decorate a class  
with an additional method

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25
@GroovyASTTransformation(phase = CompilePhase.INSTRUCTION_SELECTION) 
class AddMethodASTTransformation extends AbstractASTTransformation { 
void visit(ASTNode[] nodes, SourceUnit source) { 
ClassNode classNode = (ClassNode) nodes[1] 
 
ReturnStatement code = 
new ReturnStatement( 
new ConstantExpression("42")) 
 
MethodNode methodNode = 
new MethodNode("getMessage", 
ACC_PUBLIC, ClassHelper.make(String), 
[] as Parameter[], [] as ClassNode[], 
code) 
 
classNode.addMethod(methodNode) 
} 
}

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25
 
ReturnStatement code = 
new ReturnStatement( 
new ConstantExpression("42")) 
 
code) 
 
} 
}
return 42

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26
AST macros: the new way
 
ReturnStatement simplestCode = macro { return "42" }
 
 
 
code) 
 
} 
}

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26
 
 
 
 
code) 
 
} 
}
macro method

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26
 
 
 
 
code) 
 
} 
}
macro method
Different variants:
macro(Closure),
macro(boolean, Closure)
macro(CompilePhase,
Closure)…

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27
AST macros: variable substitution
@Target([ElementType.FIELD]) 
"metaprogramming.MD5ASTTransformation"]) 
@interface MD5 { }

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27
@Target([ElementType.FIELD]) 
"metaprogramming.MD5ASTTransformation"]) 
@interface MD5 { }
Adds a get${stringField}MD5()
method for each @MD5 String ﬁeld

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28
BlockStatement buildMD5MethodCode(FieldNode fieldNode) { 
VariableExpression fieldVar = GeneralUtils.varX(fieldNode.name) 
 
return macro(CompilePhase.SEMANTIC_ANALYSIS, true) { 
return java.security.MessageDigest 
.getInstance('MD5') 
.digest($v { fieldVar }.getBytes()) 
.encodeHex() 
.toString() 
} 
}

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28
BlockStatement buildMD5MethodCode(FieldNode fieldNode) { 
VariableExpression fieldVar = GeneralUtils.varX(fieldNode.name) 
 
return macro(CompilePhase.SEMANTIC_ANALYSIS, true) { 
return java.security.MessageDigest 
.getInstance('MD5') 
.digest($v { fieldVar }.getBytes()) 
.encodeHex() 
.toString() 
} 
}
Substitute this $v expression with  
a variable from the context

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29
AST macros: macro class
class StatisticsASTTransformation extends AbstractASTTransformation { 
ClassNode templateClass = buildTemplateClass(classNode) 
 
templateClass.methods.each { MethodNode node -> 
classNode.addMethod(node) 
} 
} 
 
ClassNode buildTemplateClass(ClassNode reference) { 
def methodCount = constX(reference.methods.size()) 
def fieldCount = constX(reference.fields.size()) 
 
return new MacroClass() { 
class Statistics { 
java.lang.Integer getMethodCount() { 
return $v { methodCount } 
} 
 
java.lang.Integer getFieldCount() { 
return $v { fieldCount } 
} 

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29
AST macros: macro class
class StatisticsASTTransformation extends AbstractASTTransformation { 
ClassNode templateClass = buildTemplateClass(classNode) 
 
templateClass.methods.each { MethodNode node -> 
classNode.addMethod(node) 
} 
} 
 
ClassNode buildTemplateClass(ClassNode reference) { 
def methodCount = constX(reference.methods.size()) 
def fieldCount = constX(reference.fields.size()) 
 
return new MacroClass() { 
class Statistics { 
java.lang.Integer getMethodCount() { 
return $v { methodCount } 
} 
 
java.lang.Integer getFieldCount() { 
return $v { fieldCount } 
} 
MacroClass not restricted to
expressions & statements:
you can generate
methods & classes

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30
Create custom macros
withLock(lock) {
// …
}

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30
withLock(lock) {
// …
}
try {
lock.lock()
// …
} finally {
lock.unlock()
}

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30
withLock(lock) {
// …
}
try {
lock.lock()
// …
} finally {
lock.unlock()
}
@Macro static Expression withLock(
MacroContext ctx, Expression lockVar,
ClosureExpression body) {
callX(closureX(
macro {
try {
$v { lockVar }.lock()
$v { body }.call()
} finally {
$v { lockVar }.unlock()
}
}
), 'call')
}

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31
AST matchers
@Target([ElementType.METHOD]) 
@GroovyASTTransformationClass(["JokingASTTransformation"]) 
@interface Joking { }

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31
AST matchers
@GroovyASTTransformation(
phase = CompilePhase.INSTRUCTION_SELECTION) 
class JokingASTTransformation
extends AbstractASTTransformation {
 
MethodNode methodNode = nodes[1] 
 
methodNode 
.getCode() 
.visit( 
new ConvertOnePlusOneToThree(source)) 
} 
}

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31
AST matchers
@GroovyASTTransformation(
phase = CompilePhase.INSTRUCTION_SELECTION) 
class JokingASTTransformation
extends AbstractASTTransformation {
 
MethodNode methodNode = nodes[1] 
 
methodNode 
.getCode() 
.visit( 
new ConvertOnePlusOneToThree(source)) 
} 
}
class ConvertOnePlusOneToThree
extends ClassCodeExpressionTransformer { 
SourceUnit sourceUnit 
 
ConvertOnePlusOneToThree(SourceUnit sourceUnit) { 
this.sourceUnit = sourceUnit 
} 
 
Expression transform(Expression exp) { 
Expression ref = macro { 1 + 1 } 
 
if (ASTMatcher.matches(ref, exp)) { 
return macro { 3 } 
} 
 
return super.transform(exp) 
} 
}

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32
AST matchers
void testTestingSumExpression() { 
use(ASTMatcher) { 
TwiceASTTransformation sample = new TwiceASTTransformation()
 
Expression referenceNode = macro { 
a + a 
}.withConstraints { 
placeholder 'a' 
} 
 
assert sample 
.sumExpression 
.matches(referenceNode) 
} 
}

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32
AST matchers
void testTestingSumExpression() { 
use(ASTMatcher) { 
TwiceASTTransformation sample = new TwiceASTTransformation()
 
Expression referenceNode = macro { 
a + a 
}.withConstraints { 
placeholder 'a' 
} 
 
assert sample 
.sumExpression 
.matches(referenceNode) 
} 
}
Placeholders to
match anything

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Groovy
“Parrot”!

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34
Good ol’ do / while loops
int i = 0 
 
do { 
println i++ 
} while (i < 10) 
 
assert i == 10

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35
Classical array initializers
def d = new double[] {}
def i = new int[] { 1, 2 }

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36
Identity comparison is back!
class Person { String name } 
 
def p1 = new Person(name: 'Marion') 
def p2 = new Person(name: 'Érine') 
def p2copy = p2  
 
assert p2 === p2copy 
assert p1 !== p2

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37
!in and !instanceof
if (!(1324 instanceof String)) {} 
if (1234 !instanceof String) {} 
 
assert !(3 in []) 
assert 3 !in []

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38
Safe indexing ?[ ]
List list = null 
assert list?[2] == null
Map map = null 
assert map?['abc'] == null

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39
Try with resources
import java.util.zip.GZIPOutputStream 
 
def input = new File('./NOTICE') 
def output = new File('/tmp/zipped.zip') 
 
// Java-style 
try ( 
FileInputStream fin = new FileInputStream(input); 
GZIPOutputStream out = new GZIPOutputStream(new FileOutputStream(output)) 
) { 
byte[] buffer = new byte[4096] 
int nread = 0 
while ((nread = fin.read(buffer)) != -1) { 
out.write(buffer, 0, nread) 
} 
}

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40
Try with resources
import java.util.zip.GZIPOutputStream 
 
def input = new File('./NOTICE') 
def output = new File('/tmp/zipped.zip') 
 
// Groovy-style :-) 
try ( 
fin = new FileInputStream(input) 
out = new GZIPOutputStream(new FileOutputStream(output)) 
) {
out << fin
}

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41
Lambdas!
import static java.util.stream.Collectors.toList 
 
(1..10).forEach((it) -> { println it }) 
 
assert (1..10).stream() 
.filter((it) -> it % 2 == 0) 
.map((it) -> it * 2) 
.collect(toList()) == [4, 8, 12, 16, 20]

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42
Lambdas!
// all the shapes
(x, y) -> x + y 
(x, y) -> { x + y } 
(int x, int y) -> x + y

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42
Lambdas!
// all the shapes
(x, y) -> x + y 
(x, y) -> { x + y } 
implicit
return

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42
Lambdas!
// all the shapes
(x, y) -> x + y 
(x, y) -> { x + y } 
def c = (int x, int y = 0) -> x + y 
assert c(1) == 1
implicit
return

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42
Lambdas!
// all the shapes
(x, y) -> x + y 
(x, y) -> { x + y } 
def c = (int x, int y = 0) -> x + y 
assert c(1) == 1
implicit
return
default
argument

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43
Method references — class refs
import static java.util.stream.Collectors.toList 
 
// class::staticMethod 
assert ['1', '2', '3'] == 
[1, 2, 3].stream() 
.map(String::valueOf) 
.collect(toList()) 
 
// class::instanceMethod 
assert ['A', 'B', 'C'] == 
['a', 'b', 'c'].stream() 
.map(String::toUpperCase) 
.collect(toList())

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44
Method references — instance refs
class Name { 
String name 
char firstLetter() { name[0] } 
static cloneOf(Name n) { new Name(name: n.name + '2') } 
}

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44
Method references — instance refs
class Name { 
String name 
char firstLetter() { name[0] } 
static cloneOf(Name n) { new Name(name: n.name + '2') } 
}
// instance::instanceMethod 
def fl = new Name(name: 'Guillaume')::firstLetter 
assert fl() == 'G' 
 
// instance::staticMethod 
def n = new Name(name: 'Marion') 
def clone = n::cloneOf 
assert clone(n).name == 'Marion2'

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45
Method references — constructor refs
def r = Random::new 
println r().nextInt(10)

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45
def r = Random::new 
println r().nextInt(10)
def arr2d = String[][]::new 
arr2d(2, 2) == [[null, null], [null, null]]

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46
import groovy.transform.Canonical 
 
@Canonical 
class Animal { 
String kind 
}

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46
import groovy.transform.Canonical 
 
@Canonical 
class Animal { 
String kind 
}
def a = Animal::new 
assert a('lion').kind == 'lion' 
 
def c = Animal 
assert c::new('cat').kind == 'cat'

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47
Elvis assignment
import groovy.transform.ToString 
 
@ToString 
class Person { 
String name 
int age 
}
def p = new Person(name: 'Érine') 
 
p.with { 
name = name ?: 'unknown' 
age = age ?: 4 
} 
 
assert p.toString() == 'Person(Érine, 4)'

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47
Elvis assignment
import groovy.transform.ToString 
 
@ToString 
class Person { 
String name 
int age 
}
def p = new Person(name: 'Érine') 
 
p.with { 
name = name ?: 'unknown' 
age = age ?: 4 
} 
 
assert p.toString() == 'Person(Érine, 4)'
p.with { 
name ?= 'unknown' 
age ?= 4 
}

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48
JavaDoc comments saved
import org.codehaus.groovy.control.* 
import static org.apache.groovy.parser.antlr4.AstBuilder.DOC_COMMENT 
 
def code = ''' 
/** 
* class Foo 
* @author glaforge 
*/ 
class Foo { 
/** a method */ 
void m(int i) {} 
} 
'''

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48
JavaDoc comments saved
import org.codehaus.groovy.control.* 
import static org.apache.groovy.parser.antlr4.AstBuilder.DOC_COMMENT 
 
def code = ''' 
/** 
* class Foo 
* @author glaforge 
*/ 
class Foo { 
/** a method */ 
void m(int i) {} 
} 
'''
def ast = new CompilationUnit().tap { 
addSource 'myscript.groovy', code 
compile Phases.SEMANTIC_ANALYSIS 
}.ast 
 
def cls = ast.classes[0]
 
assert cls.nodeMetaData[DOC_COMMENT]
.contains('class Foo') 
assert cls.methods[0].nodeMetaData[DOC_COMMENT]
.contains('a method')

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49
@Groovydoc to get javadocs at runtime
/**
* @Groovydoc
* Text content available at runtime 
*/ 
class A {}

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49
@Groovydoc to get javadocs at runtime
/**
* @Groovydoc
* Text content available at runtime 
*/ 
class A {}
assert A.class.getAnnotation(Groovydoc).value()
.contains('content available at runtime')

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What's new in Apache Groovy 2.4, 2.5, 3.0....

What's new in Apache Groovy 2.4, 2.5, 3.0....

Guillaume Laforge

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