Building DSLs with Xtext - Eclipse Modeling Day 2009

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Model-Driven Software Development with DSLs

Suppose...

You’d want to core an apple...

... for your kids.

? Right tool for the job?

Your trusty swiss army knife!

Suppose...

You’d want to core a few more apples...

... for an apple cake.

Still the best tool for the job?

Better use this one.

and this one:

... a DSL is ...

A speciﬁc tool for a speciﬁc job

Domain-Specific Language (DSL) A DSL is a formal, processable language targeting at a specific viewpoint or aspect of a software system. Its semantics, flexibility and notation is designed in order to support working with that viewpoint as good as possible.

Rd2-c2

“ Queen to c7. Check.” “ Rd2-c2 , ” rook at d2 moves to c2.

Moves in Chess: !ook at a1 moves to a5. P iece S q uare A ction De stin ation "ishop at c8 captures knight at h3. P iece S q uare ion Action D es tinat # b1 x c3 Piece S qua re ction stination AD e $2 - g4 ation S A D quar e ction e stin

Rook a1 move a5 Bishop c8 capture h3 Knight Knight b1 capture c3 Queen Pawn g2 move g4 Game Move Source «enum» WhitePlayer * Destination Piece BlackPlayer Piece

"ishop at c8 captures knight at h3 " c8 x h3

Model (textﬁle) White: "Mayfield" Black: "Trinks" pawn at e2 moves to e4 pawn at f7 moves to g5 K b1 - c3 f7 - f5 queen at d1 moves to h5 // 1-0

Xtext is a complete environment for development of textual - programming languages and - domain-speciﬁc languages. It is implemented in Java and is based on Eclipse, EMF, and Antlr.

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

Demo • Model File within Editor + Custom View • Xtext Grammar for writing simple chess games • Derived meta model • Java program that works with textual models • Xpand-based generator © itemis AG 2009 – All rights reserved 31

Real World DSLs

Regular Expressions

[-+]?[0-9]*.?[0-9]+

Complex Event Processing

from FlightBookings F, CarBookings C, HotelBookings H matching [24 hours: F, C, H ] on F.name = C.name = H.name select F.name, true bookingWithCar, into TripleBookings from FlightBookings F, CarBookings C, HotelBookings H matching [24 hours: F, !C, H ] on F.name = C.name = H.name select F.name, false bookingWithCar into TripleBookings from TripleBookings where prev(bookingWithCar) and not bookingWithCar select name into LostCustomers

internal DSL (with Java)

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

Entities by Example vs.

package templates; import java.util.*; import java.io.Serializable; import javax.persistence.*; @SuppressWarnings("serial") @Entity public class Customer implements Serializable { ! private Long id; ! private String name; ! private Address address; ! private Set<Order> orders = new HashSet<Order>(); ! // No-arg constructor ! public Customer() { ! } ! @Id ! public Long getId() { ! ! return id; ! } ! public void setId(Long id) { ! ! this.id = id; ! } ! public String getName() { ! ! return name; ! } ! public void setName(String name) { ! ! this.name = name; ! } ! public Address getAddress() { ! ! return address; ! } ! public void setAddress(Address address) { ! ! this.address = address; ! } ! @OneToMany ! public Collection<Order> getOrders() { ! ! return orders; ! } ! public void setOrders(Set<Order> orders) { ! ! this.orders = orders; ! } }

package templates; import java.io.Serializable; import java.util.*; import javax.persistence.*; @SuppressWarnings("serial") @Entity public class Customer implements Serializable { ! private Long id; ! private String name; ! private Address address; ! private Set<Order> orders = new HashSet<Order>(); ! // No-arg constructor ! public Customer() { ! } ! @Id ! public Long getId() { ! ! return id; ! } ! public void setId(Long id) { ! ! this.id = id; ! } ! public String getName() { ! ! return name; ! } ! public void setName(String name) { ! ! this.name = name; ! } ! public Address getAddress() { ! ! return address; ! } ! public void setAddress(Address address) { ! ! this.address = address; ! } ! @OneToMany ! public Collection<Order> getOrders() { ! ! return orders; ! } ! public void setOrders(Set<Order> orders) { ! ! this.orders = orders; ! } }

entity Customer { ! property name : String ! property address : Address ! property orders : Order[] } POJOs DAOs

The Finder Method

<entity name="Customer"> <attribute type="String" name="name"/> <findMethod name="findFixed"> <expression> <equals> <attributeRef attr="name"/> <constant val="John Doe"/> </equals> </expression> <findMethod> </entity> entity Customer { ! property name : String ! finder findFixed : name = "John Doe" }

Demo ! Implement simple Entity DSL ! Use prepared Generator

grammar org.xtext.webinar.Entity ! with org.eclipse.xtext.common.Terminals entity generate entity "http://www.xtext.org/webinar/Entity" Model Model: types ! (elements+=Type)*; * Type: Type name: EString ! SimpleType | Entity; SimpleType: ! 'type' name=ID; SimpleType Entity Entity: extends ! 'entity' name=ID ('extends' extends=[Entity])? '{' properties ! ! properties+=Property* * ! '}'; Property name: EString type many: EBoolean Property: ! 'property' name=ID ':' type=[Type] (many?='[]')?;

Pimp my Write

Whitespace-Aware Languages

Incremental Generation

Conclusion

Abstraction

Use a DSL to develop your tools

Support Newsgroup Community Forum Professional Support

twitter @HBehrens blog http://HeikoBehrens.net mail Heiko.Behrens@itemis.de xing http://www.xing.com/proﬁle/Heiko_Behrens linkedin http://www.linkedin.com/in/HeikoBehrens www.xtext.org The Committer Team twitter @Xtext Heiko Michael Sven Moritz Peter Dennis Jan Patrick Knut Sebastian Behrens Clay Efftinge Eysholdt Friese Hübner Köhnlein Schönbach Wannheden Zarnekow

Building DSLs with Xtext - Eclipse Modeling Day 2009

by Heiko Behrens

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