Groovy DSLs 教学课件.ppt

Groovy DSLs Prototyping Textual, Domain-Specific Languages in the Groovy Programming Language Chris.vanBuskirk@vanderbilt.edu 1-Feb-2008 A Forgivable Half-Truth Groovy is a superset of Java Wraps Java’s OO paradigm and byte code virtual machine with : Dynamically typed scripting language Lots of syntatic sugar and first-class support for computing with lists and maps Closures Hello World println hello world public class hello_world extends groovy.lang.Script { … public static void main (java.lang.String[] args) { System.out.println(“hello world”); } … } SwingBuilder: A DSL for UIs SwingBuilder in Action MySimpleDsl.groovy MySimpleDsl in Action Not Really a DSL Yet Mostly just executing a script that the user provides at run-time. The Groovy compiler does the job of parsing for us (i.e. no BNF grammars) ALSO: Groovy = Java + Meta-Programming Meta-Object Protocol (inspired by Smalltalk and Lisp)meta-classes intercept method invocation property accessat run time Expando-MOP Example // Simple, Expando-MOP Technique java.lang.Integer.metaClass.getEuro = { - delegate * ExchangeRates_2018.EUROS_PER_DOLLAR } java.lang.Integer.metaClass.getDollars = { - delegate } assert 1.euro == 10.dollars // i.e. getEuro( ) class ExchangeRates_2018 { def static final EUROS_PER_DOLLAR = 10 } A “Time” DSL Slightly More Complicated Example MyTimeDsl in Action MyTimeDsl.groovy Starting to Look Like a DSL !!! M$-Inbox Query Language Overriding the ‘|’ Operator InboxQL.groovy Sorting By User-Defined Keys * * Institute for Software Integrated Systems Vanderbilt University ? 2008, Vanderbilt University Class MetaClass new behavior default behavior obj.someMethod( ) *