Domain Specific Language - DSL

Örnek

Gramer şöyle olsun. Burada ilginç olan Word1. Hem gramer Word1 ile bitebiliyor hem de optional word ile bitebiliyor.

Grammar ::= ( 
  'SINGLE-WORD' | 
  'PARAMETERISED-WORD' '('[A-Z]+')' |
  'WORD1' 'OPTIONAL-WORD'? | 
  'WORD2' ( 'WORD-CHOICE-A' | 'WORD-CHOICE-B' ) | 
  'WORD3'+ 
)

Elimizde şöyle bir DSL olsun.

// Initial interface, entry point of the DSL
// Depending on your DSL's nature, this can also be a class with static
// methods which can be static imported making your DSL even more fluent
interface Start {
  End singleWord();
  End parameterisedWord(String parameter);
  Intermediate1 word1();
  Intermediate2 word2();
  Intermediate3 word3();
}
 
// Terminating interface, might also contain methods like execute();
interface End {
  void end();
}
 
// Intermediate DSL "step" extending the interface that is returned
// by optionalWord(), to make that method "optional"
interface Intermediate1 extends End {
  End optionalWord();
}
 
// Intermediate DSL "step" providing several choices (similar to Start)
interface Intermediate2 {
  End wordChoiceA();
  End wordChoiceB();
}
 
// Intermediate interface returning itself on word3(), in order to allow
// for repetitions. Repetitions can be ended any time because this 
// interface extends End
interface Intermediate3 extends End {
  Intermediate3 word3();
}

Şöyle yaparız

Start start = ...
 
start.singleWord().end();
start.parameterisedWord("abc").end();
 
start.word1().end();
start.word1().optionalWord().end();
 
start.word2().wordChoiceA().end();
start.word2().wordChoiceB().end();
 
start.word3().end();
start.word3().word3().end();
start.word3().word3().word3().end();