O slideshow foi denunciado.
Utilizamos seu perfil e dados de atividades no LinkedIn para personalizar e exibir anúncios mais relevantes. Altere suas preferências de anúncios quando desejar.

groovy transforms

Learn about using Groovy's built-in AST transforms and writing your own

  • Entre para ver os comentários

groovy transforms

  1. 1. SPRINGONE2GX WASHINGTON, DC Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution -NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Groovy AST Transformations Dr Paul King @paulk_asert http://slideshare.net/paulk_asert/groovy-transforms https://github.com/paulk-asert/groovy-transforms
  2. 2. Apache Groovy Groovy in Action 2nd edition Manning promo code: ctwspringo2gx http://www.manning.com/koenig2 2
  3. 3. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Contents 3  Introduction • Built-in AST Transforms • Writing your own transforms
  4. 4. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Parsing Summary 4 public run() ... L1 ALOAD 1 LDC 1 AALOAD ALOAD 0 LDC "Howdy Y'all" INVOKEINTERFACE callCurrent() ARETURN ... println "Howdy Y'all" BlockStatement -> ReturnStatement -> MethodCallExpression -> VariableExpression("this") -> ConstantExpression("println") -> ArgumentListExpression -> ConstantExpression("Howdy Y'all") MyScript.groovy > groovy MyScript.groovy > groovyc MyScript.groovy > groovysh > groovyConsole
  5. 5. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 5 Parsing Summary • 9 phase compiler – Early stages: read source code and convert into a sparse syntax tree – Middle stages: iteratively build up a more dense and information rich version of the syntax tree – Later stages: check the tree and convert it into byte code/class files Initialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization
  6. 6. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 6 Parsing - Early StagesInitialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization @ToString class Greeter { String message = "Howdy Y'all" void greet() { println message } } ClassNode: Greeter MethodNode: greet Property: message type: unresolved(String) AnnotationNode: ToString type: unresolved(ToString) methods: properties: annotations: BlockStatement MethodCall: this.println(message)
  7. 7. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 7 Parsing - Middle StagesInitialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization ClassNode: Greeter MethodNode: greet FieldNode: message type: resolved(String) methods: fields: constructors: ConstructorNode MethodNode: getMessage MethodNode: setMessage MethodNode: toString MethodNode: getMetaClass …
  8. 8. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 8 Parsing - Final StagesInitialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization public greet()V ... L1 ... ALOAD 0 GETFIELD Greeter.message INVOKEINTERFACE callCurrent() POP ...
  9. 9. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 9 When are transforms applied? Initialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization Local Transformations Global Transformations
  10. 10. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 10 1 + 2 + 3
  11. 11. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 11 1 + 2 + 3
  12. 12. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 12 1 + 2 + 3 assert 1 + 1 == 2
  13. 13. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Contents 13 • Introduction  Built-in AST Transforms • Writing your own transforms
  14. 14. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 14 @ToString @groovy.transform.ToString class Detective { String firstName, lastName } def d = new Detective(firstName: 'Sherlock', lastName: 'Holmes') assert d.toString() == 'Detective(Sherlock, Holmes)' class Detective { String firstName, lastName String toString() { def _result = new StringBuilder() _result.append('Detective(') _result.append(this.firstName) _result.append(', ') _result.append(this.lastName) _result.append(')') return _result.toString() } } ToStringASTTransformation
  15. 15. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 15 @ToString annotation parameters… Parameter Name Purpose excludes Name of properties (list or comma separated) to exclude from toString(). By default, all properties are included. Incompatible with “includes”. includes Name of properties (list or comma separated) to include in toString(). Incompatible with “excludes”. includeSuper Include the toString() for the super class by setting to true. Default: false. includeNames Include the names of the properties by setting this parameter to true. Default: false. allProperties Whether JavaBean "properties" are included.2.5
  16. 16. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 16 …@ToString annotation parameters Parameter Name Purpose includeFields Include fields, not just properties. Default: false. ignoreNulls Exclude any properties that are null. By default null values will be included. includePackage Print just the simple name of the class without the package. By default the package name is included. cache Set to true to cache toString() calculations. Use only for immutable objects. By default the value is recalculated upon each method call. includeSuperProperties Include properties from super class. Default: false
  17. 17. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 17 @ToString (using parameters) @ToString(ignoreNulls=true, excludes='lastName', includeNames=true, includePackage=false, includeFields=true) class Detective { String firstName, lastName List clues private nemesis = 'Moriarty' } def d = new Detective(firstName: 'Sherlock', lastName: 'Holmes') assert d.toString() == 'Detective(firstName:Sherlock, nemesis:Moriarty)'
  18. 18. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 18 @EqualsAndHashCode @EqualsAndHashCode class Actor { String firstName, lastName } def a1 = new Actor(firstName: 'Ian', lastName: 'McKellen') def a2 = new Actor(firstName: 'Ian', lastName: 'McKellen') assert !(a1.is(a2)) assert a1 == a2 EqualsAndHashCodeASTTransformation
  19. 19. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 19 @EqualsAndHashCode class Actor { String firstName, lastName int hashCode() { def _result = HashCodeHelper.initHash() _result = HashCodeHelper.updateHash(_result, this.firstName) _result = HashCodeHelper.updateHash(_result, this.lastName) return _result } boolean canEqual(other) { return other instanceof Actor } ...
  20. 20. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 20 ... boolean equals(other) { if (other == null) return false if (this.is(other)) return true if (!( other instanceof Actor)) return false Actor otherTyped = (Actor) other if (!(otherTyped.canEqual(this))) return false if (!(this.getFirstName().is(otherTyped.getFirstName()))) { if (!(this.getFirstName() == otherTyped.getFirstName())) { return false } } if (!(this.getLastName().is(otherTyped.getLastName()))) { if (!(this.getLastName() == otherTyped.getLastName())) { return false } } return true } } @EqualsAndHashCod e
  21. 21. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 21 @EqualsAndHashCode annotation parameters…Parameter Name Purpose excludes Exclude certain properties from the calculation by specifying them as a comma separated list or literal list of String name values. This is commonly used with an object that has an 'id' field. By default, no properties are excluded. Incompatible with “includes” includes Include only a specified list of properties by specifying them as a comma separated list or literal list of String name values. Incompatible with “excludes”. cache Set to true to cache hashCode() calculations. Use only for immutable objects. By default the hashCode() is recalculated whenever the hashCode() method is called.
  22. 22. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 22 …@EqualsAndHashCode annotation parametersParameter Name Purpose callSuper Include properties from the super class by setting this parameter to true. By default, the super class is not used as part of the calculation. includeFields Include the class's fields, not just the properties, in the calculation by setting this parameter to true. By default, fields are not taken into account. useCanEqual Set to false to disable generation of a canEqual() method to be used by equals(). By default the canEqual() method is generated. The canEqual idiom provides a mechanism for permitting equality in the presence of inheritance hierarchies. For immutable classes with no explicit super class, this idiom is not required.
  23. 23. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 23 @MapConstructor • How does Groovy normally handle "named" arguments class Athlete { String first, last } def a1 = new Athlete( first: 'Michael', last: 'Jordan') assert a1.first == 'Michael' 2.5 def a1 = new Athlete() a1.setFirst('Michael') a1.setLast('Jordan')
  24. 24. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 24 @MapConstructor • With @MapConstructor we have an explicit Map constructor • Good for Java integration & final fields @MapConstructor class Athlete { String first, last } def a1 = new Athlete( first: 'Michael', last: 'Jordan') assert a1.first == 'Michael' 2.5 Athlete(Map m) { if (m.containsKey('first')) { first = m.get('first') } if (m.containsKey('last')) { last = m.get('last') } }
  25. 25. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 25 @MapConstructor annotation parameters… Parameter Name Purpose excludes Exclude certain properties from the constructor. Incompatible with “includes” includes Include only a specified list of properties in the constructor. Incompatible with “excludes” pre A Closure containing statements which will be prepended to the generated constructor post A Closure containing statements which will be appended to the end of the generated constructor 2.5
  26. 26. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 26 …@MapConstructor annotation parameters Parameter Name Purpose includeFields Include the class's fields, not just the properties, in the calculation by setting this parameter to true. By default, fields are not taken into account. includeProperties Include properties in the constructor. Default: true includeSuperProperties Include properties from super classes in the constructor useSetters By default, properties are set directly using their respective field but a setter can be used instead if desired 2.5
  27. 27. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 27 @MapConstructor import groovy.transform.* @ToString(includeFields=true, includeNames=true) @MapConstructor(post={ full = "$first $last" }) class Person { final String first, last private final String full } assert new Person(first: 'Dierk', last: 'Koenig').toString() == 'Person(first:Dierk, last:Koenig, full:Dierk Koenig)' 2.5
  28. 28. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 28 @TupleConstructor • A traditional positional arguments constructor @TupleConstructor class Athlete { String first, last } def a1 = new Athlete('Michael', 'Jordan') def a2 = new Athlete('Michael') def a3 = new Athlete(first: 'Michael') assert a1.first == a2.first assert a2.first == a3.first
  29. 29. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 29 @TupleConstructor annotation parameters… Parameter Name Purpose excludes Exclude certain properties from the constructor. Incompatible with “includes” includes Include only a specified list of properties in the constructor. Incompatible with “excludes” callSuper Should super properties be called within a call to the parent constructor rather than set as properties force By default, this annotation becomes a no-op if you provide your own constructor, this flag forces constructor creation defaults Used to set whether default value processing is enabled (the default) or disabled 2.5
  30. 30. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 30 …@TupleConstructor annotation parameters Parameter Name Purpose includeFields Include the class's fields, not just the properties, in the calculation by setting this parameter to true. By default, fields are not taken into account. includeProperties Include properties in the constructor. Default: true includeSuperFields Include fields from super classes in the constructor includeSuperProperties Include properties from super classes in the constructor useSetters By default, properties are set directly using their respective field but a setter can be used instead if desired 2.5
  31. 31. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 31 @TupleConstructor @TupleConstructor class Athlete { String first, last } def a1 = new Athlete('Michael', 'Jordan') def a2 = new Athlete('Michael') def a3 = new Athlete(first: 'Michael') assert a1.first == a2.first assert a2.first == a3.first
  32. 32. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 32 @TupleConstructor @TupleConstructor class Athlete { String first, last } def a1 = new Athlete('Michael', 'Jordan') def a2 = new Athlete('Michael') def a3 = new Athlete(first: 'Michael') assert a1.first == a2.first assert a2.first == a3.first class Athlete { String first, last Athlete(String first=null, String last=null) {…} }
  33. 33. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 33 @TupleConstructor @TupleConstructor class Athlete { String first, last } def a1 = new Athlete('Michael', 'Jordan') def a2 = new Athlete('Michael') def a3 = new Athlete(first: 'Michael') assert a1.first == a2.first assert a2.first == a3.first class Athlete { String first, last Athlete(String first=null, String last=null) {…} } class Athlete { String first, last Athlete(String first, String last) {…} Athlete(String first) {…} Athlete() {…} }
  34. 34. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 34 @TupleConstructor @TupleConstructor(defaults=false) class Athlete { String first, last } def a1 = new Athlete('Michael', 'Jordan') def a2 = new Athlete('Michael') def a3 = new Athlete(first: 'Michael') class Athlete { String first, last Athlete(String first, String last) {…} }
  35. 35. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 35 @Canonical • Combines @ToString, @EqualsAndHashCode and @TupleConstructor • Actually uses AnnotationCollector in Groovy 2.5 @Canonical class Inventor { String firstName, lastName } def i1 = new Inventor('Thomas', 'Edison') def i2 = new Inventor('Thomas') assert i1 != i2 assert i1.firstName == i2.firstName assert i1.toString() == 'Inventor(Thomas, Edison)' 2.5
  36. 36. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 36 @Canonical • Combines @ToString, @EqualsAndHashCode and @TupleConstructor • Actually uses AnnotationCollector in Groovy 2.5 @AnnotationCollector(value=[ToString, TupleConstructor, EqualsAndHashCode], mode=AnnotationCollectorMode.PREFER_EXPLICIT_MERGED) public @interface Canonical { } 2.5
  37. 37. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 37 @Canonical • Combines @ToString, @EqualsAndHashCode and @TupleConstructor • Actually uses AnnotationCollector in Groovy 2.5 @AnnotationCollector(value=[ToString, TupleConstructor, EqualsAndHashCode], mode=AnnotationCollectorMode.PREFER_EXPLICIT_MERGED) public @interface Canonical { } @Canonical(includeNames=false) @ToString(excludes='last', includeNames=true) class Person { String first, last String getInitials() { "${first[0]}${last[0]}" } } assert new Person(first: 'Dierk', last: 'Koenig').toString() == 'Person(first:Dierk, initials:DK)' 2.5
  38. 38. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 38 @AnnotationCollector @AnnotationCollector @ToString(excludes='id,first', includeNames=true) @EqualsAndHashCode @TupleConstructor(excludes='id') @interface MyCanonical {} @MyCanonical class Person { UUID id = UUID.randomUUID() String first, last } def agent = new Person('James', 'Bond') assert agent.toString() == 'Person(last:Bond)'
  39. 39. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 39 @Lazy… • Safe and efficient deferred construction • Understands double checked-locking and holder class idioms // nominally expensive resource with stats class Resource { private static alive = 0 private static used = 0 Resource() { alive++ } def use() { used++ } static stats() { "$alive alive, $used used" } }
  40. 40. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 40 …@Lazy class ResourceMain { def res1 = new Resource() @Lazy res2 = new Resource() @Lazy static res3 = { new Resource() }() @Lazy(soft=true) volatile Resource res4 } new ResourceMain().with { assert Resource.stats() == '1 alive, 0 used' res2.use() res3.use() res4.use() assert Resource.stats() == '4 alive, 3 used' assert res4 instanceof Resource def expected = 'res4=java.lang.ref.SoftReference' assert it.dump().contains(expected) }
  41. 41. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 41 @InheritConstructors • Reduced boiler-plate for scenarios where parent classes have multiple constructors (e.g. Exceptions & PrintWriter) @InheritConstructors class MyPrintWriter extends PrintWriter { } def pw1 = new MyPrintWriter(new File('out1.txt')) def pw2 = new MyPrintWriter('out2.txt', 'US-ASCII') [pw1, pw2].each { it << 'foo' it.close() } assert new File('out1.txt').text == new File('out2.txt').text ['out1.txt', 'out2.txt'].each{ new File(it).delete() }
  42. 42. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 42 @Sortable… • Reduced boiler-plate for Comparable classes including specialised Comparators @Sortable(includes = 'last,initial') class Politician { String first Character initial String last String initials() { first[0] + initial + last[0] } }
  43. 43. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 43 …@Sortable // @Sortable(includes = 'last,initial') class Politician { ... } def politicians = [ new Politician(first: 'Margaret', initial: 'H', last: 'Thatcher'), new Politician(first: 'George', initial: 'W', last: 'Bush') ] politicians.with { assert sort()*.initials() == ['GWB', 'MHT'] def comparator = Politician.comparatorByInitial() assert toSorted(comparator)*.initials() == ['MHT', 'GWB'] }
  44. 44. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 44 @Builder • Recent Java idiom is to use "fluent-api" builders • Often not needed for Groovy • But if you need Java integration or want improved IDE support… @Builder class Chemist { String first, last int born } def builder = Chemist.builder() def c = builder.first("Marie").last("Curie").born(1867).build()
  45. 45. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 45 @Builder • Supports customizable building strategies DefaultStrategy Creates a nested helper class with methods for each property and a build() method SimpleStrategy Creates chainable setters, i.e. each setter returns the object itself ExternalStrategy For creating a builder for a class you don’t have control over, e.g. from a library or another team in your organization. InitializerStrateg y Like DefaultStrategy but when used with @CompileStatic allows type- safe object creation
  46. 46. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 46 @Delegate class Clock { void tellTime() { println '7 am' } } class Alarm { void soundAlarm() { println 'Time to wake up' } } class AlarmClock { @Delegate Clock c = new Clock() @Delegate Alarm a = new Alarm() } new AlarmClock().with { tellTime(); soundAlarm() }
  47. 47. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 47 @Delegate class Clock { void tellTime() { println '7 am' } } class Alarm { void soundAlarm() { println 'Time to wake up' } } class AlarmClock { @Delegate Clock c = new Clock() @Delegate Alarm a = new Alarm() } new AlarmClock().with { tellTime(); soundAlarm() } class AlarmClock { private Clock c = new Clock() private Alarm a = new Alarm() void tellTime() { c.tellTime() } void soundAlarm() { a.soundAlarm() } }
  48. 48. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 48 @Memoized • For making pure functions more efficient class Calc { def log = [] @Memoized int sum(int a, int b) { log << "$a+$b" a + b } } new Calc().with { assert sum(3, 4) == 7 assert sum(4, 4) == 8 assert sum(3, 4) == 7 assert log.join(' ') == '3+4 4+4' }
  49. 49. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 49 @TailRecursive • For unravelling recursion import groovy.transform.TailRecursive class RecursiveCalc { @TailRecursive int accumulate(int n, int sum = 0) { (n == 0) ? sum : accumulate(n - 1, sum + n) } } new RecursiveCalc().with { assert accumulate(10) == 55 }
  50. 50. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 50 @TailRecursiveclass RecursiveCalc { int accumulate(int n, int sum) { int _sum_ = sum int _n_ = n while (true) { if (_n_ == 0) { return _sum_ } else { int __n__ = _n_ int __sum__ = _sum_ _n_ = __n__ - 1 _sum_ = __sum__ + __n__ } } } int accumulate(int n) { accumulate(n, 0) } }
  51. 51. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 51 @Immutable • For unchanging data structures @Immutable class Genius { String firstName, lastName } def g1 = new Genius(firstName: 'Albert', lastName: "Einstein") assert g1.toString() == 'Genius(Albert, Einstein)' def g2 = new Genius('Leonardo', "da Vinci") assert g2.firstName == 'Leonardo' shouldFail(ReadOnlyPropertyException) { g2.lastName = 'DiCaprio' }
  52. 52. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 52 @Log @Log4j @Log4j2 @Commons @Slf4j • For easy logging @groovy.util.logging.Log class Database { def search() { log.fine(runLongDatabaseQuery()) } def runLongDatabaseQuery() { println 'Calling database' /* ... */ return 'query result' } } new Database().search()
  53. 53. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 53 @Synchronized • For safe synchronization class PhoneBook1 { private final phoneNumbers = [:] @Synchronized def getNumber(key) { phoneNumbers[key] } @Synchronized void addNumber(key, value) { phoneNumbers[key] = value } }
  54. 54. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 54 @WithReadLock @WithWriteLock • Declarative and efficient synchronization class PhoneBook2 { private final phoneNumbers = [:] @WithReadLock def getNumber(key) { phoneNumbers[key] } @WithWriteLock def addNumber(key, value) { phoneNumbers[key] = value } }
  55. 55. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 55 @AutoClone (Simple example) • Easier cloning. With multiple styles supported: because one size doesn't fit all for cloning on the JVM @AutoClone class Chef1 { String name List<String> recipes Date born } def name = 'Heston Blumenthal' def recipes = ['Snail porridge', 'Bacon & egg ice cream'] def born = Date.parse('yyyy-MM-dd', '1966-05-27') def c1 = new Chef1(name: name, recipes: recipes, born: born) def c2 = c1.clone() assert c2.recipes == recipes
  56. 56. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 56 @AutoClone (Advanced example) @TupleConstructor @AutoClone(style=COPY_CONSTRUCTOR) class Person { final String name final Date born } @TupleConstructor(includeSuperProperties=true, callSuper=true) @AutoClone(style=COPY_CONSTRUCTOR) class Chef2 extends Person { final List<String> recipes } def name = 'Jamie Oliver' def recipes = ['Lentil Soup', 'Crispy Duck'] def born = Date.parse('yyyy-MM-dd', '1975-05-27') def c1 = new Chef2(name, born, recipes) def c2 = c1.clone() assert c2.name == name && c2.born == born && c2.recipes == recipes
  57. 57. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 57 @AutoCloneStyle Style Description CLONE Adds a clone() method to your class. The clone() method will call super.clone() before calling clone() on each Cloneable property of the class. Doesn’t provide deep cloning. Not suitable if you have final properties. (Default) SIMPLE Adds a clone() method to your class which calls the no-arg constructor then copies each property calling clone() for each Cloneable property. Handles inheritance hierarchies. Not suitable if you have final properties. Doesn’t provide deep cloning. COPY_CONSTRUCTOR Adds a “copy” constructor, i.e. one which takes your class as its parameter, and a clone() method to your class. The copy constructor method copies each property calling clone() for each Cloneable property. The clone() method creates a new instance making use of the copy constructor. Suitable if you have final properties. Handles inheritance hierarchies. Doesn’t provide deep cloning. SERIALIZATION Adds a clone() method to your class which uses serialization to copy your class. Suitable if your class already implements the Serializable or Externalizable interface. Automatically performs deep cloning. Not as time or memory efficient. Not suitable if you have final properties.
  58. 58. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 58 @AutoExternalize @AutoExternalize @ToString class Composer { String name int born boolean married } def c = new Composer(name: 'Wolfgang Amadeus Mozart', born: 1756, married: true) def baos = new ByteArrayOutputStream() baos.withObjectOutputStream{ os -> os.writeObject(c) } def bais = new ByteArrayInputStream(baos.toByteArray()) def loader = getClass().classLoader def result bais.withObjectInputStream(loader) { result = it.readObject().toString() } assert result == 'Composer(Wolfgang Amadeus Mozart, 1756, true)'
  59. 59. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 59 @TimedInterrupt @ThreadInterrupt @ConditionalInterrupt • For safer scripting • Typically applied through compilation customizers to user scripts rather than directly used
  60. 60. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Contents 60 • Introduction • Built-in AST Transforms  Writing your own transforms
  61. 61. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 61 Parsing Deep Dive • Purpose Read source files/streams and configure compiler • Key classes CompilerConfiguration CompilationUnit Initialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization
  62. 62. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 62 • Purpose Use (ANTLR) grammar to convert source code into token tree • Key classes CompilationUnit GroovyLexer GroovyRecognizer GroovyTokenTypes • CST Transforms – http://java.dzone.com/articles/groovy- antlr-plugins-better Parsing Deep DiveInitialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization
  63. 63. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 63 Parsing Deep Dive • Purpose Token tree converted into abstract syntax tree (AST) and is the first place where we can begin to write AST visitors • Key classes AntlrParserPlugin EnumVisitor • AST Transforms @Grab (global) Initialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization
  64. 64. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 64 Parsing Deep Dive • Purpose Resolves classes and performs consistency and validity checks beyond what the grammar can provide • Key classes StaticVerifier ResolveVisitor StaticImportVisitor InnerClassVisitor, AnnotationCollector • AST Transforms @Lazy @Builder @Field @Log @Memoized @PackageScope @TailRecursive @BaseScript Initialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization
  65. 65. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 65 Parsing Deep Dive • Purpose Finalizes the complete abstract syntax tree and typically the last point at which you want to run a transformation • Key classes InnerClassCompletionVisitor EnumCompletionVisitor, TraitComposer • AST Transforms @Bindable @Vetoable @Mixin @AutoClone @ConditionalInterrupt @ThreadInterrupt @TimedInterrupt @ListenerList @Canonical @Category @Delegate @Bindable @Vetoable @EqualsAndHashCode @AutoExternalize @Immutable @IndexedProperty @Synchronized @InheritConstructors @Sortable @WithReadLock @WithWriteLock @Singleton @Newify @ToString @TupleConstructor Initialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization
  66. 66. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 66 • Purpose Chooses an instruction set for the generated bytecode, e.g. Java 5 versus pre-Java 5 • AST Transforms @CompileStatic @TypeChecked Parsing Deep DiveInitialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization
  67. 67. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 67 Parsing Deep Dive • Purpose Creates bytecode based Class in memory • Key classes OptimizerVisitor GenericsVisitor Verifier LabelVerifier ExtendedVerifier ClassCompletionVerifier AsmClassGenerator Initialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization
  68. 68. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 68 Parsing Deep Dive • Purpose Binary output (.class file) written to file system Initialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization
  69. 69. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 69 Parsing Deep Dive • Purpose Used to cleanup any resources no longer needed Initialization Semantic Analysis Instruction Selection Parsing Conversion Canonicalization Class Generation Output Finalization
  70. 70. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Visitor Pattern… • separates the object being walked (the tree) from the behavior of the walker (the visitor) 70
  71. 71. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ …Visitor Pattern • Consider extending ClassCodeVisitorSupport but also consider extending AbstractASTTransformation or using ClassCodeExpressionTransformer 71
  72. 72. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Writing a Local AST Transform… • Create an Annotation • Annotated with @GroovyASTTransformationClass 72 class MainTransformation{} import org.codehaus.groovy.transform.GroovyASTTransformationClass import java.lang.annotation.* @Retention(RetentionPolicy.SOURCE) @Target([ElementType.METHOD]) @GroovyASTTransformationClass(classes = [MainTransformation]) public @interface Main {}
  73. 73. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ …Writing a Local AST Transform… • Write your transform class 73 @GroovyASTTransformation(phase = CompilePhase.INSTRUCTION_SELECTION) class MainTransformation implements ASTTransformation { private static final ClassNode[] NO_EXCEPTIONS = ClassNode.EMPTY_ARRAY private static final ClassNode STRING_ARRAY = ClassHelper.STRING_TYPE.makeArray() void visit(ASTNode[] astNodes, SourceUnit sourceUnit) { // use guard clauses as a form of defensive programming if (!astNodes) return if (!astNodes[0] || !astNodes[1]) return if (!(astNodes[0] instanceof AnnotationNode)) return if (astNodes[0].classNode?.name != Main.class.name) return if (!(astNodes[1] instanceof MethodNode)) return ...
  74. 74. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ …Writing a Local AST Transform… 74 ... MethodNode annotatedMethod = astNodes[1] ClassNode declaringClass = annotatedMethod.declaringClass def callMethod = callX(ctorX(declaringClass), annotatedMethod.name) Statement body = block(stmt(callMethod)) def visibility = ACC_STATIC | ACC_PUBLIC def parameters = params(param(STRING_ARRAY, 'args')) declaringClass.addMethod('main', visibility, VOID_TYPE, parameters, NO_EXCEPTIONS, body) } }
  75. 75. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ …Writing a Local AST Transform • Use the transform 75 class Greeter { @Main def greet() { println "Hello from the greet() method!" } }
  76. 76. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ …Writing a Local AST Transform • Use the transform 76 class Greeter { @Main def greet() { println "Hello from the greet() method!" } } new GroovyShell(getClass().classLoader).evaluate ''' class Greeter { @Main def greet() { println "Hello from the greet() method!" } } '''
  77. 77. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Creating AST… • By hand (raw) • Verbose, full IDE supported 77 import org.codehaus.groovy.ast.* import org.codehaus.groovy.ast.stmt.* import org.codehaus.groovy.ast.expr.* new ReturnStatement( new ConstructorCallExpression( ClassHelper.make(Date), ArgumentListExpression.EMPTY_ARGUMENTS ) )
  78. 78. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ …Creating AST… • By hand (with helper utility methods) • Concise, not everything has concise form (yet) 78 import static org.codehaus.groovy.ast.tools.GeneralUtils.* import static org.codehaus.groovy.ast.ClassHelper.* returnS(ctorX(make(Date)))
  79. 79. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ …Creating AST… • With ASTBuilder (from a specification/DSL) • Requires AST knowledge, limited IDE support 79 import org.codehaus.groovy.ast.builder.AstBuilder def ast = new AstBuilder().buildFromSpec { returnStatement { constructorCall(Date) { argumentList {} } } }
  80. 80. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ …Creating AST… • With ASTBuilder (from a String) • Concise, intuitive, can't create everything, limited IDE support 80 import org.codehaus.groovy.ast.builder.AstBuilder def ast = new AstBuilder().buildFromString('new Date()')
  81. 81. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ …Creating AST… • With ASTBuilder (from code) • Clear, concise, some entities cannot be created, IDE assistance 81 import org.codehaus.groovy.ast.builder.AstBuilder def ast = new AstBuilder().buildFromCode { new Date() }
  82. 82. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ …Creating AST • ASTBuilder limitations • Great for prototyping, not always suitable for production transforms • Groovy technology, can be slow, subject to global transforms • Sometimes wasteful, e.g. you might need to create more than you need such as creating a whole class to then pull out one method • Some flavors don't support arbitrary node types, don't make it easy to handle interactions with existing class nodes, don't make it easy to support redirects or generics, nor allow you to properly set the line/column numbers resulting in difficult to debug AST transform and cryptic compilation errors 82
  83. 83. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Feature Interactions • Consider Groovy's @ToString annotation transform which runs at the end of the Canonicalization phase • Now suppose we want to create a @Trace annotation transform which when placed on a class will "instrument" each method with "trace" println statements, e.g. this: becomes: • What behaviour should I expect calling toString() if @Trace runs at the end of Semantic Analysis? Canonicalization? Instruction Selection? 83 def setX(x) { this.x = x } def setX(x) { println "setX begin" this.x = x println "setX end" }
  84. 84. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Testing AST Transforms • Consider using ASTTest • Test both the AST tree and the end-to-end behavior • Consider writing defensive guards • Use GroovyConsole 84
  85. 85. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Design Considerations • Don't reuse ClassNodes • Compile-time vs Runtime trade-offs and typing • Feature Interactions/Fragility • Beware Complexity • Risks of introducing bugs • Avoid global transforms (unless needed) • GroovyConsole is your friend (AST/bytecode) • Use addError for errors • Retain line/column number information when transforming • Watch variable scoping 85
  86. 86. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Further Information • Documentation • http://docs.groovy-lang.org/docs/groovy- latest/html/documentation/#_compile_time_metaprogramming • Macro Groovy • https://github.com/bsideup/MacroGroovy • https://github.com/bsideup/groovy-macro-methods • AST Workshop • http://melix.github.io/ast-workshop/ 86
  87. 87. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ More Information: Groovy in Action, 2ed 87 Manning promo code: ctwspringo2gx
  88. 88. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Bonus Material
  89. 89. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 89 Groovy and "fluent-api" builders • A common idiom in recent times for Java is to use an inner helper class and accompanying "fluent-api" to reduce ceremony when creating Java classes with many parameters – But Groovy's named parameters greatly reduces this need class Chemist { String first String last int born } def c = new Chemist(first: "Marie", last: "Curie", born: 1867) assert c.first == "Marie" assert c.last == "Curie" assert c.born == 1867
  90. 90. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 90 @Builder… • But if you need Java integration or want improved IDE support… import groovy.transform.builder.Builder @Builder class Chemist { String first String last int born } def builder = Chemist.builder() def c = builder.first("Marie").last("Curie").born(1867).build() assert c.first == "Marie" assert c.last == "Curie" assert c.born == 1867
  91. 91. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 91 …@Builder… • And it supports customizable building strategies Strategy Description DefaultStrategy Creates a nested helper class for instance creation. Each method in the helper class returns the helper until finally a build() method is called which returns a created instance. SimpleStrategy Creates chainable setters, i.e. each setter returns the object itself after updating the appropriate property. ExternalStrategy Allows you to annotate an explicit builder class while leaving some buildee class being built untouched. This is appropriate when you want to create a builder for a class you don’t have control over, e.g. from a library or another team in your organization. InitializerStrategyCreates a nested helper class for instance creation which when used with @CompileStatic allows type-safe object creation.
  92. 92. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 92 …@Builder • Type-safe construction using phantom types (*if* you need it) @Builder(builderStrategy=InitializerStrategy) @Immutable class Chemist { String first, last int born } @CompileStatic def solution() { def init = Chemist.createInitializer().first("Marie").last("Curie").born(1867) new Chemist(init).with { assert first == "Marie" assert last == "Curie" assert born == 1867 } } solution()
  93. 93. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 93 @Delegate (motivation) • Anything wrong with this? class NoisySet extends HashSet { @Override boolean add(item) { println "adding $item" super.add(item) } @Override boolean addAll(Collection items) { items.each { println "adding $it" } super.addAll(items) } }
  94. 94. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 94 @Delegate (motivation) • Anything wrong with this? • Could we fix this implementation? class NoisySet extends HashSet { @Override boolean add(item) { println "adding $item" super.add(item) } @Override boolean addAll(Collection items) { items.each { println "adding $it" } super.addAll(items) } }
  95. 95. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 95 @Delegate (motivation) • Anything wrong with this? • Could we fix this implementation? • What about using the delegate pattern written by hand? class NoisySet extends HashSet { @Override boolean add(item) { println "adding $item" super.add(item) } @Override boolean addAll(Collection items) { items.each { println "adding $it" } super.addAll(items) } }
  96. 96. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 96 @Delegate • For declarative but flexible use of the delegate pattern class NoisySet { @Delegate Set delegate = new HashSet() @Override boolean add(item) { println "adding $item" delegate.add(item) } @Override boolean addAll(Collection items) { items.each { println "adding $it" } delegate.addAll(items) } } Set ns = new NoisySet() ns.add(1) ns.addAll([2, 3]) assert ns.size() == 3
  97. 97. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 97 @Delegate annotation parameters… Parameter Name Purpose interfaces Set this parameter to true to make the owner class implement the same interfaces as the delegate, which is the default behavior. To make the owner not implement the delegate interfaces, set this parameter to false. deprecated Set this parameter to true to have the owner class delegate methods marked as @Deprecated in the delegate. By default @Deprecated methods are not delegated. methodAnnotations Set to true if you want to carry over annotations from the methods of the delegate to your delegating method. By default, annotations are not carried over. Currently Closure annotation members are not supported. parameterAnnotations Set to true if you want to carry over annotations from the method parameters of the delegate to your delegating method. By default, annotations are not carried over. Currently Closure annotation members are not supported.
  98. 98. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 98 …@Delegate annotation parameters Only one of 'includes', 'includeTypes', 'excludes' or 'excludeTypes' should be used Parameter Name Purpose excludes List of method and/or property names to exclude when delegating. excludeTypes List of interfaces containing method signatures to exclude when delegating. includes List of method and/or property names to include when delegating. includeTypes List of interfaces containing method signatures to exclude when delegating.
  99. 99. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 99 @Memoized • For making pure functions more efficient class Calc { def log = [] @Memoized int sum(int a, int b) { log << "$a+$b" a + b } } new Calc().with { assert sum(3, 4) == 7 assert sum(4, 4) == 8 assert sum(3, 4) == 7 assert log.join(' ') == '3+4 4+4' }
  100. 100. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 100 @TailRecursive • For unravelling recursion import groovy.transform.TailRecursive class RecursiveCalc { @TailRecursive int accumulate(int n, int sum = 0) { (n == 0) ? sum : accumulate(n - 1, sum + n) } } new RecursiveCalc().with { assert accumulate(10) == 55 }
  101. 101. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 101 @TailRecursiveclass RecursiveCalc { int accumulate(int n, int sum) { int _sum_ = sum int _n_ = n while (true) { if (_n_ == 0) { return _sum_ } else { int __n__ = _n_ int __sum__ = _sum_ _n_ = __n__ - 1 _sum_ = __sum__ + __n__ } } } int accumulate(int n) { accumulate(n, 0) } }
  102. 102. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 102 @Immutable • For unchanging data structures @Immutable class Genius { String firstName, lastName } def g1 = new Genius(firstName: 'Albert', lastName: "Einstein") assert g1.toString() == 'Genius(Albert, Einstein)' def g2 = new Genius('Leonardo', "da Vinci") assert g2.firstName == 'Leonardo' shouldFail(ReadOnlyPropertyException) { g2.lastName = 'DiCaprio' }
  103. 103. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 103 @Log @Log4j @Log4j2 @Commons @Slf4j • For easy logging @groovy.util.logging.Log class Database { def search() { log.fine(runLongDatabaseQuery()) } def runLongDatabaseQuery() { println 'Calling database' /* ... */ return 'query result' } } new Database().search()
  104. 104. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 104 @Synchronized • For safe synchronization class PhoneBook1 { private final phoneNumbers = [:] @Synchronized def getNumber(key) { phoneNumbers[key] } @Synchronized void addNumber(key, value) { phoneNumbers[key] = value } }
  105. 105. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 105 @WithReadLock @WithWriteLock • Declarative and efficient synchronization class PhoneBook2 { private final phoneNumbers = [:] @WithReadLock def getNumber(key) { phoneNumbers[key] } @WithWriteLock def addNumber(key, value) { phoneNumbers[key] = value } }
  106. 106. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 106 @AutoClone (Simple example) • Easier cloning. With multiple styles supported: because one size doesn't fit all for cloning on the JVM @AutoClone class Chef1 { String name List<String> recipes Date born } def name = 'Heston Blumenthal' def recipes = ['Snail porridge', 'Bacon & egg ice cream'] def born = Date.parse('yyyy-MM-dd', '1966-05-27') def c1 = new Chef1(name: name, recipes: recipes, born: born) def c2 = c1.clone() assert c2.recipes == recipes
  107. 107. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 107 @AutoClone (Advanced example) @TupleConstructor @AutoClone(style=COPY_CONSTRUCTOR) class Person { final String name final Date born } @TupleConstructor(includeSuperProperties=true, callSuper=true) @AutoClone(style=COPY_CONSTRUCTOR) class Chef2 extends Person { final List<String> recipes } def name = 'Jamie Oliver' def recipes = ['Lentil Soup', 'Crispy Duck'] def born = Date.parse('yyyy-MM-dd', '1975-05-27') def c1 = new Chef2(name, born, recipes) def c2 = c1.clone() assert c2.name == name && c2.born == born && c2.recipes == recipes
  108. 108. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 108 @AutoCloneStyle Style Description CLONE Adds a clone() method to your class. The clone() method will call super.clone() before calling clone() on each Cloneable property of the class. Doesn’t provide deep cloning. Not suitable if you have final properties. (Default) SIMPLE Adds a clone() method to your class which calls the no-arg constructor then copies each property calling clone() for each Cloneable property. Handles inheritance hierarchies. Not suitable if you have final properties. Doesn’t provide deep cloning. COPY_CONSTRUCTOR Adds a “copy” constructor, i.e. one which takes your class as its parameter, and a clone() method to your class. The copy constructor method copies each property calling clone() for each Cloneable property. The clone() method creates a new instance making use of the copy constructor. Suitable if you have final properties. Handles inheritance hierarchies. Doesn’t provide deep cloning. SERIALIZATION Adds a clone() method to your class which uses serialization to copy your class. Suitable if your class already implements the Serializable or Externalizable interface. Automatically performs deep cloning. Not as time or memory efficient. Not suitable if you have final properties.
  109. 109. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 109 @AutoExternalize @AutoExternalize @ToString class Composer { String name int born boolean married } def c = new Composer(name: 'Wolfgang Amadeus Mozart', born: 1756, married: true) def baos = new ByteArrayOutputStream() baos.withObjectOutputStream{ os -> os.writeObject(c) } def bais = new ByteArrayInputStream(baos.toByteArray()) def loader = getClass().classLoader def result bais.withObjectInputStream(loader) { result = it.readObject().toString() } assert result == 'Composer(Wolfgang Amadeus Mozart, 1756, true)'
  110. 110. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 110 @TimedInterrupt @ThreadInterrupt @ConditionalInterrupt • For safer scripting • Typically applied through compilation customizers to user scripts rather than directly used
  111. 111. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 111 @TimedInterrupt @TimedInterrupt(value = 520L, unit = MILLISECONDS) class BlastOff1 { def log = [] def countdown(n) { sleep 100 log << n if (n == 0) log << 'ignition' else countdown(n - 1) } } def b = new BlastOff1() Thread.start { try { b.countdown(10) } catch (TimeoutException ignore) { b.log << 'aborted' } }.join() assert b.log.join(' ') == '10 9 8 7 6 aborted'
  112. 112. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 112 @ThreadInterrupt @ThreadInterrupt class BlastOff2 { def log = [] def countdown(n) { Thread.sleep 100 log << n if (n == 0) log << 'ignition' else countdown(n - 1) } } def b = new BlastOff2() def t1 = Thread.start { try { b.countdown(10) } catch(InterruptedException ignore) { b.log << 'aborted' } } sleep 570 t1.interrupt() t1.join() assert b.log.join(' ') == '10 9 8 7 6 aborted'
  113. 113. Unless otherwise indicated, these slides are © 2013 -2015 ASERT and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 113 @ConditionalInterrupt @ConditionalInterrupt({ count <= 5 }) class BlastOff3 { def log = [] def count = 10 def countdown() { while (count != 0) { log << count count-- } log << 'ignition' } } def b = new BlastOff3() try { b.countdown() } catch (InterruptedException ignore) { b.log << 'aborted' } assert b.log.join(' ') == '10 9 8 7 6 aborted'

×