Groovy in the light of Java 8 -- SpringOne2GX 2014
How can Groovy developers can benefit from Java 8?
What are the differences between Java 8 and Groovy?
How does Groovy go beyond what Java 8?
Is Groovy still relevant now that we have Java 8?
But more precisely… • Will Java lambdas replace Groovy closures? • What are the differences between them? ! • Will Groovy support all the new Java 8 language constructs? • lambdas, default methods, method references… ! • How Groovy developers can benefit from Java 8? ! • What does Groovy offer beyond Java 8? 8
What we’re going to talk about • What’s new in Java 8 • new syntax constructs • new APIs ! • Similar concepts in Groovy • and how they compare or complement ! • What Groovy offers in addition • beyond Java, Groovy adds its own twist! 11
Lambda expressions 20 double highestScore = students .filter(Student s -> s.getGradYear() == 2011) .map(Student s -> s.getScore()) .max(); There’s no function type!
Lambda expressions 20 double highestScore = students .filter(Student s -> s.getGradYear() == 2011) .map(Student s -> s.getScore()) .max(); Pipeline being built Single pass!
The various lambda syntaxes 22 String name -> name.length() ! (int left, int right) -> left + right ! (String left, String sep, String right) -> { System.out.println(left + sep + right) } One parameter: no parens Expression on right: no curly
The various lambda syntaxes 22 String name -> name.length() ! (int left, int right) -> left + right ! (String left, String sep, String right) -> { System.out.println(left + sep + right) } Parentheses required for more that one parameter
The various lambda syntaxes 23 name -> name.length() ! (left, right) -> left + right ! (left, sep, right) -> { System.out.println(left + sep + right) } Clever type inference can help get rid of parameter type declarations
Beyond: Closure default parameters 25 def mult = { int a, int b = 10 -> a * b } ! assert mult(2, 3) == 6 assert mult(5) == 50 Default value if the parameter is not specified
Beyond: Duck typing polymorphism 26 def adder = { a, b -> a + b } ! assert adder(100, 200) == 300 assert adder('X', 'Y') == 'XY' Works both for numbers and for strings
Static methods in interfaces • You can put static utility methods in interfaces, instead of in companion classes (like « Collections ») 39 public interface Stream { // ... static Stream empty() { return new Stream { ... } } }
Groovy Traits • Like interfaces, but with method bodies • similar to Java 8 interface default methods • Elegant way to compose behavior • multiple inheritance without the « diamond » problem • Traits can also be stateful • traits can have properties like normal classes • Compatible with static typing and static compilation • class methods from traits also visible from Java classes • Also possible to implement traits at runtime 41
Annotations on types • Everywhere you can put a type, you can put an annotation 48 @NonNull String name; ! email = (@Email String) input; ! List<@NonNull String> names; ! new @Interned MyObject(); ! void monitorTemperature() throws @Critical TemperatureException { ... } ! class UnmodifiableList implements @Readonly List<@Readonly T> {...}
Annotations on types • Everywhere you can put a type, you can put an annotation 48 @NonNull String name; ! email = (@Email String) input; ! List<@NonNull String> names; ! new @Interned MyObject(); ! void monitorTemperature() throws @Critical TemperatureException { ... } ! class UnmodifiableList implements @Readonly List<@Readonly T> {...} Not yet supported
Annotations on types • Everywhere you can put a type, you can put an annotation 48 @NonNull String name; ! email = (@Email String) input; ! List<@NonNull String> names; ! new @Interned MyObject(); ! void monitorTemperature() throws @Critical TemperatureException { ... } ! class UnmodifiableList implements @Readonly List<@Readonly T> {...} Imagine the potential for targets for local AST transformations?
Annotations on types • Everywhere you can put a type, you can put an annotation 48 @NonNull String name; ! email = (@Email String) input; ! List<@NonNull String> names; ! new @Interned MyObject(); ! void monitorTemperature() throws @Critical TemperatureException { ... } ! class UnmodifiableList implements @Readonly List<@Readonly T> {...}
Groovy compile-time meta-annotations 49 import groovy.transform.AnnotationCollector ! @Service @Transactional @AnnotationCollector public @interface TransactionalService {} ! @TransactionalService class MyTransactionalService {} Can handle parameters (even conflicting), or you can create your own « processor »
Date / Time API 52 LocalDate.now(); today.with(TemporalAdjusters.lastDayOfMonth()).minusDays(2); ! LocalDate.of(2012, Month.MAY, 14); dateOfBirth.plusYears(1); ! LocalDate date = LocalDate.of(2000, Month.NOVEMBER, 20); LocalDate nextWed = date.with(TemporalAdjusters.next(DayOfWeek.WEDNESDAY)); Groovy could add some operator overloading?
Groovy truth, null handling, Elvis with Optional 63 def maybeName = Optional.of("Guillaume") ! def result = maybeName ?: "unknown" ! if (maybeName) { println maybeName.get() } else { println "unknown" } ! maybeName?.toUpperCase() Interesting discussions on the mailing-list to further enhance usage of Optional from Groovy
Android support • You can use Groovy to code Android apps! • use Groovy 2.4.0-beta-1+ • prefer @CompileStatic ! • Two great posts to get started: • http://melix.github.io/blog/2014/06/grooid.html • http://melix.github.io/blog/2014/06/grooid2.html 78
What does NYT likes about Groovy on Android? • No Java 8, no lambda on Android… 80 Func0 func = new Func0() { @Override public String call() { return "my content"; } }; Async.start(func);
What does NYT likes about Groovy on Android? • No Java 8, no lambda on Android… 81 ! ! ! ! ! ! Async.start { "my content" } Good bye annonymous inner classes!
What does NYT likes about Groovy on Android? ! • Groovy code more concise and more readable ! • but just as type-safe as needed! (with @TypeChecked) ! • but just as fast as needed! (with @CompileStatic) 82
Grails — web framework 86 @Grab("com.h2database:h2:1.3.173") import grails.persistence.* ! @Entity @Resource(uri='/books') class Book { String title } One class, one command, and you’ve got a full REST CRUD application!
Ant + XML 96 def writer = new StringWriter() def mkp = new MarkupBuilder(writer) ! mkp.html { head { title 'Build notification' } body { p 'Your build was successful' } } ! new AntBuilder().mail(mailhost: 'localhost', messagemimetype: 'text/html', subject: 'Build successful') { ! from address: '[email protected]' to address: '[email protected]' message writer attchments { fileset(dir: 'dist') { include name: '**/logs*.txt' } } }
Ant + XML 96 def writer = new StringWriter() def mkp = new MarkupBuilder(writer) ! mkp.html { head { title 'Build notification' } body { p 'Your build was successful' } } ! new AntBuilder().mail(mailhost: 'localhost', messagemimetype: 'text/html', subject: 'Build successful') { ! from address: '[email protected]' to address: '[email protected]' message writer attchments { fileset(dir: 'dist') { include name: '**/logs*.txt' } } } Generate some HTML with the XML support
Ant + XML 96 def writer = new StringWriter() def mkp = new MarkupBuilder(writer) ! mkp.html { head { title 'Build notification' } body { p 'Your build was successful' } } ! new AntBuilder().mail(mailhost: 'localhost', messagemimetype: 'text/html', subject: 'Build successful') { ! from address: '[email protected]' to address: '[email protected]' message writer attchments { fileset(dir: 'dist') { include name: '**/logs*.txt' } } } Generate some HTML with the XML support Use the Ant builder and the mail task
Ant + XML 96 def writer = new StringWriter() def mkp = new MarkupBuilder(writer) ! mkp.html { head { title 'Build notification' } body { p 'Your build was successful' } } ! new AntBuilder().mail(mailhost: 'localhost', messagemimetype: 'text/html', subject: 'Build successful') { ! from address: '[email protected]' to address: '[email protected]' message writer attchments { fileset(dir: 'dist') { include name: '**/logs*.txt' } } } Generate some HTML with the XML support Use the Ant builder and the mail task Use the Ant’s fileset
JSON support — creating JSON 97 import groovy.json.* ! def json = new JsonBuilder() json.person { name 'Guillaume' age 37 daughters 'Marion', 'Erine' address { street '1 Main Street' zip 75001 city 'Paris' } }
Template module — new markup template engine • Based on the principles of Groovy’s « builders » • and particularly the MarkupBuilder class for generating arbitrary XML / HTML payloads ! • Compiled statically for fast template rendering ! • Internationalization aware • provide the desired Locale in the configuration object • usual suffix notation template_fr_FR.tpl ! • Custom base template class • ability to provide reusable methods across your templates 99
Template module — new markup template engine • Based on the principles of Groovy’s « builders » • and particularly the MarkupBuilder class for generating arbitrary XML / HTML payloads ! • Compiled statically for fast template rendering ! • Internationalization aware • provide the desired Locale in the configuration object • usual suffix notation template_fr_FR.tpl ! • Custom base template class • ability to provide reusable methods across your templates 99 Spring Boot approved
Markup template engine — the idea 100 cars { cars.each { car(make: it.make, name: it.name) } } model = [cars: [ new Car(make: 'Peugeot', name: '508'), new Car(make: 'Toyota', name: 'Prius’) ]] Feed a model into your template
Questions still open: Syntax support for… • lambdas • not necessarily, (confusing / duplication) ! • method references • enhance method closures • or replace them with method references ! • interface default methods • yes: traits methods aren’t default methods • repeated annotations • yes: not urgent • but less boilerplate is good ! • annotations on type • yes: opens up new possibilities for targets of local AST transformation ! • interface static methods • yes: for Java compatibility 107
Further possible API enhancements • Make Optional Groovy-friendly • with regards to Groovy Truth • accessing the wrapped value ! • More Groovy methods for… • NIO • Streams • Date / time ! • Operator overloading for Date / time • for arithmetics on instants and durations 108
Further possible API enhancements • Make Optional Groovy-friendly • with regards to Groovy Truth • accessing the wrapped value ! • More Groovy methods for… • NIO • Streams • Date / time ! • Operator overloading for Date / time • for arithmetics on instants and durations 108 Community feedback & contributions welcome!
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