GR8Conf 2011: GContracts
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GContracts is a Groovy library that implements Design by Contract using annotations. It allows specifying preconditions, postconditions, and class invariants using annotations like @Requires, @Ensures, and @Invariant. These annotations take closure expressions that are evaluated at compile-time and run-time to check conditions. GContracts works with Groovy 1.6 and higher and has features like labeling, interface contracts, inheritance support, and integration with Grails.
GR8Conf 2011: GContracts
- 1. GContracts Andre Steingress @sternegross/@gcontracts
- 10. www.ejug.at
- 12. GCONTRACTS DESIGN BY CONTRACT (tm) FOR GROOVY Groovy 1.7+ (was 1.6 loooong time ago) BSD LICENSE https://github.com/andresteingress/gcontracts
- 13. JUMP START.
- 14. LET‘S REVIEW THIS ACCOUNT CLASS. Googled, found at javacoffeebreak.com
- 15. PREREQUISITES.
- 16. @Grab( group='org.gcontracts', module='gcontracts-core', version='[1.2.3,)' ) no additional dependencies...
- 18. 3 ANNOTATIONS.
- 19. Commonalities • special assertion types • specifying boolean expressions • closure instances as annotation parameters @MyAnnotation({ param?.size() > 0 })
- 20. @Requires • precondition • a method‘s bouncer
- 21. @Ensures • postcondition • a method‘s mother
- 22. @Invariant • class-invariant • an object‘s god.
- 23. LET‘S REVIEW THIS ACCOUNT CLASS. Googled, found at javacoffeebreak.com
- 24. INTERNALS.
- 25. @Ensures({ count() == old.count + 1 }) { count() == old.count + 1 } { result, old -> assert count() == old.count + 1 } compile-time class $_gc_closure1 extends Closure { def doCall(...) { // ... assert count() == old.count + 1 // ... } } @Requires($_gc_213123123123.class)
- 26. JVM Arguments: -ea -da if ($GCONTRACTS_ENABLED) { ... } org.gcontracts.ViolationTracker.init() $_gc_result = Putable$_gc_closure1.newInstance(this, run-time this).call(element, key) if (org.gcontracts.ViolationTracker.violationsOccured()) org.gcontracts.ViolationTracker.rethrowFirst()
- 27. Officially Supported since Groovy 1.8!
- 28. Works since Groovy 1.6 http://pniederw.wordpress.com/2010/03/04/3/
- 29. MORE FEATURES.
- 30. LABELING
- 33. INHERITANCE ✓INTERFACE CONTRACTS ✓ABSTRACT CLASSES ✓CONCRETE CLASSES ✓MIXED
- 35. MICRO CONTRACTS REUSABLE CONTRACT PART
- 36. MICRO CONTRACTS
- 37. Grails Integration • Container extends object construction time • @Service stereotype causes CI validation in @PostConstruct
- 41. ABOUT CONTRACTS.
- 44. WHY CONTRACTS?
- 45. SPOCK, JUNIT, et. al. ARE „THE CHINAMAN IS NOT THE ISSUE HERE, DUDE.“
- 46. External API Changes New Programmers Changing Requirements Assumptions Additional Libraries New Use-Cases More Clients New Knowledge Code Conventions
- 47. External API Changes New Programmers Changing Requirements Assumptions Additional Libraries New Use-Cases More Clients New Knowledge Code Conventions
- 48. WHAT DID YOU PROGRAM LAST WEEK? CAN YOU RECALL YOUR THOUGHTS, MODELS? WHY SHOULD ANYONE ELSE KNOW ABOUT THEM?
- 51. Thank you!
- 52. "Design by Contract" is a trademark of Interactive Software Engineering.