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Overallpresenta3on
Introduc3ontoDomainSpecificLanguagesanditstechniques.AswellasshowingFluentValida3onFrameworkconcep3onprocess.
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DomainSpecificLanguage(DSL)isaprogramminglanguagededicatedtosolveproblemsofanspecificdomain
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whichcanbetechnical
SQL HQL CSS
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orbusinessrelated.
Banking Manufacturing
Logis3cs
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ADSLcanbeinternalorexternal.
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ExternalDSLsareself‐contained
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whileinternalDSLsremainontopofotherprogramminglanguages.
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Inotherwords,internalDSLsareAPIs.
That's why they're also known as Fluent Interfaces!
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DSLsallowyoutoexpressdomainsclearly.
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Forexample,whileabusinessanalystofabankingdomainwouldsay
Transfer 5.000,00 from Client A's cash account to Client B's savings account.
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AcommonJAVAimplementa3oncouldbe
bankService.transfer(5000.00, clientA.getCashAccount(), clientB.getSavingsAccount());
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AnexternalDSLcouldexpressthesameas
transfer 5000 from clientA.cashAccount to clientB.savingsAccount
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AndaninternalDSLinJAVAcouldlooklike
bankService.execute( new Transfer() .of(5000) .from(clientA.cashAccount()) .to(clientB.savingsAccount()));
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It’snotaboutonesinglemethod
publicTransferof(doublevalue);
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butanen3remeaningfulopera3on.
new Transfer() .of(5000) .from(clientA.cashAccount()) .to(clientB.savingsAccount())
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SometechniquestodefineinternalDSLs
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MethodChaining
new Transfer() .of(5000) .from(clientA.cashAccount()) .to(clientB.savingsAccount())
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NestedFunc3on
bankService.transfer(5000, from(clientA.cashAccount()), to(clientB.savingsAcount()));
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ObjectScoping
bankService.execute( new Transfer(){{ of(5000); from(clientA.cashAccount()); to(clientB.savingsAccount()); }});
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FluentValida3onFrameworkisalabprojectapplyingFluentInterfacestothe
domainofcodevalida3on.
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Mainideawaschangingvalida3onslike
if(arg0 == null) throw new IllegalArgumentException();
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tosomethinglike
ensure(arg0).isNotNull();
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Howtochangeexcep3onmessage?
ensure(arg0).isNotNull().otherwise("arg0 cannot be null"); //doesn't work
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Triggermethodattheendoftheexpression
ensure(arg0).isNotNull().now();
ensure(arg0).isNotNull() .otherwise() .throwThis( new IllegalStateException()) .now();
//not cool!
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Anotherop3onwascrea3ngtwoentrypoints
ensure(arg0).isNotNull();
analyse(arg0).and().throwThis(new IllegalStateException()).ifNull();
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Mixingmethodchainingwithnestedfunc3ons
ensure(myObject).is(inValidState());
analyse(systemReport).and(notifyByEmail()).ifIsNot(operatingWell());
thesolu3onbecameextensible!
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Todaywesaw
DSLsarecool! ExternalDSLsarehardtoimplement FluentInterfacesandInternalDSLsarethesamething FluentInterfacesworkgreatforextensivelyusedAPIs
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That’sallfolks!
projecthXp://fluval.sourceforge.net bloghXp://blog.danielgazineu.com
email/gtalkdanielgazineu@gmail.com
twiXer@danielgazineu
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