Jazoon 2010 - Building DSLs with Eclipse

Building DSLs with Eclipse Peter Friese, itemis @peterfriese @xtext www.itemis.de (c) 2009 Peter Friese. Distributed under the EDL V1.0 - http://www.eclipse.org/org/documents/edl-v10.php More info: http://www.peterfriese.de / http://www.itemis.com

Think about your job!

Feel like this?

Because

Because you need to write

Because you need to write lots of boring code?

Wrong Level of Abstraction! http://www.ﬂickr.com/photos/rykerstribe/3222969466/

DSL o p a m e n a c g i i u n f a i g c e

DSL A language... ...that lets you express your intention ... that solves one problem ... that doesn’t get in your way ... that ﬁts your situation ... that’s formal and processable ... that’s simple and easy to learn

Some DSLs you might have heard of

select name, salary from employees where salary > 2000 order by salary

External or Internal

Internal DSLs

Mailer.mail() .to(“you@gmail.com”) .from(“me@gmail.com”) .subject(“Writing DSLs in Java”) .body(“...”) .send();

Simple

Limited

External DSLs

1)Create ANTLR grammar 2)Generate lexer / parser 3)Parser will create parse tree 4)Transform parse tree to semantic model 5)Iterate model 6)Pass model element(s) to template

Lack of symbolic integration Writing parsers / generators is complicated IDE support is inferior / non-existent

Flexible

Adaptable

Complicated

Why not use a DSL... ... for building DSLs?

http://www.eclipse.org/Xtext/ @xtext

ar Model m m ra G Generator Runtime Superclass Subclass Class LL(*) Parser ECore meta model Editor

Grammar (similar to EBNF) grammar org.xtext.example.Entity with org.eclipse.xtext.common.Terminals generate entity "http://www.xtext.org/example/Entity" Model: (types+=Type)*; Type: TypeDef | Entity; TypeDef: "typedef" name=ID ("mapsto" mappedType=JAVAID)?; JAVAID: name=ID("." ID)*; Entity: "entity" name=ID ("extends" superEntity=[Entity])? "{" (attributes+=Attribute)* "}"; Attribute: type=[Type] (many?="*")? name=ID;

grammar org.xtext.example.Entity with org.eclipse.xtext.common.Terminals Meta model inference generate entity "http://www.xtext.org/example/Entity" entity Rules -> Classes Model: (types+=Type)*; Model Type: TypeDef | Entity; types TypeDef: * Type "typedef" name=ID name: EString ("mapsto" mappedType=JAVAID)?; superEntity JAVAID: name=ID("." ID)*; TypeDef Entity Entity: mappedType attributes "entity" name=ID Attribute ("extends" superEntity=[Entity])? JAVAID name: EString "{" name: EString many: EBoolean (attributes+=Attribute)* "}"; type Attribute: type=[Type] (many?="*")? name=ID;

grammar org.xtext.example.Entity with org.eclipse.xtext.common.Terminals Meta model inference generate entity "http://www.xtext.org/example/Entity" entity Alternatives -> Hierarchy Model: (types+=Type)*; Model Type: TypeDef | Entity; types TypeDef: * Type "typedef" name=ID name: EString ("mapsto" mappedType=JAVAID)?; superEntity JAVAID: name=ID("." ID)*; TypeDef Entity Entity: mappedType attributes "entity" name=ID Attribute ("extends" superEntity=[Entity])? JAVAID name: EString "{" name: EString many: EBoolean (attributes+=Attribute)* "}"; type Attribute: type=[Type] (many?="*")? name=ID;

grammar org.xtext.example.Entity with org.eclipse.xtext.common.Terminals Meta model inference generate entity "http://www.xtext.org/example/Entity" entity Assignment -> Feature Model: (types+=Type)*; Model Type: TypeDef | Entity; types TypeDef: * Type "typedef" name=ID name: EString ("mapsto" mappedType=JAVAID)?; superEntity JAVAID: name=ID("." ID)*; TypeDef Entity Entity: mappedType attributes "entity" name=ID Attribute ("extends" superEntity=[Entity])? JAVAID name: EString "{" name: EString many: EBoolean (attributes+=Attribute)* "}"; type Attribute: type=[Type] (many?="*")? name=ID;

Let’s build a DSL for Mobile Apps

Building DSLs 1. Analyze problem domain 2. Map concepts of problem domain to language 3. (Optional: write interpreter) 4. (Optional: write generator)

Analyzing the problem domain http://www.ﬂickr.com/photos/miniﬁg/3174009125/

Anatomy of an iPhone app View title Speaker Table view Name Image Title Session Table cell Location Tab bar Entity Tab bar button Data Provider

Mapping concepts tabbarApplication jazoonApp { button { Entity title= "Schedule" icon= "83-calendar.png" Data Provider view= ScheduleList( AllSessions() ) } button { Tab bar title= "Speakers" icon= "112-group.png" Tab bar button view= SpeakerList( AllSpeakers() ) } Table view button { title= "Topics" View title icon= "44-shoebox.png" view= TopicList( AllTopics() ) Table cell } }

Mapping concepts entity Speaker { String speakerId String name Entity String bio String organization String country Data Provider String smallImageURL String largeImageURL Tab bar } Session[] talks Tab bar button entity Session { String talkId String title Table view String abstract String ^type View title String location String startTime String endTime Table cell Speaker[] speakers Topic[] topics } entity Topic { String topicId String themeId String name }

Mapping concepts Entity contentprovider AllSessions returns Session[] Data Provider fetches XML from "http://jipa.netcetera.ch/talks.xml" Tab bar selects "feed.entry" Tab bar button contentprovider AllSpeakers returns Speaker[] fetches XML Table view from "http://jipa.netcetera.ch/speakers.xml" selects "feed.entry" View title Table cell

Mapping concepts contentprovider AllSessions returns Session[] fetches XML Entity from "http://query.yahooapis.com/v1/public/ yql?q=use%20%22http%3A%2F%2FHeikoBehrens.net Data Provider %2Fjazoon%2Ftalks.xml%22%20as%20talks%3B%0Aselect %20*%20from%20talks%20where%20omitDetails Tab bar %3D1&debug=true" selects "query.results.talks.talk" Tab bar button contentprovider SessionsByTopic(String id) returns Session[] Table view fetches XML from ("http://query.yahooapis.com/v1/public/ View title yql?q=use%20%22http%3A%2F%2FHeikoBehrens.net %2Fjazoon%2Ftalks.xml%22%20as%20s%3B%0Aselect%20* Table cell %20from%20s%20where%20topicId%20%3D %20%22"id"%22&diagnostics=true&debug=true&debug=true ") selects "query.results.talks.talk"

Mapping concepts Entity Data Provider tableview ScheduleList(Session[] sessions) { title= "Schedule" Tab bar section { cell Subtitle foreach sessions as session { Tab bar button text= session.title details= session.startTime action= SessionDetails( Table view SessionById(session.talkId)) } View title } } Table cell

Demo 1

Mapping concepts to code

«Xpand»

Protected regions Debugger Editor Outlets Proﬁler Cartridges Polymorphism Type safe Produces any Can run standalone kind of text Eclipse-based (ANT / Maven)

Mapping concepts to code

Mapping concepts to code tableview SpeakerList( Speaker[] speakers) { title= "Speakers" section { cell Default foreach speakers as speaker { text= speaker.name image= speaker.smallImageURL action= SpeakerDetails (SpeakerById( speaker.speakerId)) } } }

Mapping concepts to code tableview SpeakerList( «DEFINE viewModule FOR Speaker[] speakers) SectionedView» { «FILE filenameModule()» title= "Speakers" #import "«filenameHeader()»" section #import "NSObject+Applause.h" { «EXPAND imports» cell Default foreach speakers as speaker @implementation «className()» { text= speaker.name «EXPAND sectionCount» image= speaker.smallImageURL «EXPAND sectionTitleHeader» action= SpeakerDetails «EXPAND rowCounts» (SpeakerById( «EXPAND cellDescriptions» speaker.speakerId)) «EXPAND cellSelections» } «EXPAND staticData» } @end } «ENDFILE» «ENDDEFINE»

Demo 2

3 things to take home

3 things to take home 1 Implementing DSLs is easy with Xtext 2 Xtext delivers great IDE support 3 Symbolic integration is possible

More Info? Xtext Webinar: http://live.eclipse.org/node/886 www.xtext.org Consulting: http://www.itemis.com @peterfriese | http://peterfriese.de

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Jazoon 2010 - Building DSLs with Eclipse

by Peter Friese

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