Building DSLs with
Eclipse
Peter Friese, itemis
@peterfriese
@xtext
(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

What is a DSL?

Domain

Language

Suppose...

You’d want to core an apple...

... for your kids.

?
Right tool for the job?

Your trusty swiss army knife!

Because you can use it for other stuff, too.
E.g., opening a bottle of wine.

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:

BUT
avoid the unitasker!

BUT
avoid the unitasker!

... a DSL is ...

A specific tool
for a specific job

A specific tool
for a specific job

Samples for DSLs

SQL

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

ANT

<project name="MyProject" default="dist" basedir=".">
<property name="src" location="src"/>
<property name="build" location="build"/>
<property name="dist" location="dist"/>
<target name="init">
<mkdir dir="${build}"/>
</target>
<target name="compile" depends="init">
<javac srcdir="${src}" destdir="${build}"/>
</target>
<target name="dist" depends="compile">
<mkdir dir="${dist}/lib"/>
<jar jarfile="${dist}/lib/MyProject.jar"
basedir="${build}"/>
</target>
<target name="clean">
<delete dir="${build}"/>
<delete dir="${dist}"/>
</target>
</project>

<project name="MyProject" default="dist" basedir=".">
<property name="src" location="src"/>
<property name="build" location="build"/>
<property name="dist" location="dist"/>
<target name="init">
<mkdir dir="${build}"/>
</target>
<target name="compile" depends="init">
<javac srcdir="${src}" destdir="${build}"/>
</target>
<target name="dist" depends="compile">
<mkdir dir="${dist}/lib"/>
<jar jarfile="${dist}/lib/MyProject.jar"
basedir="${build}"/>
</target>
<target name="clean">
<delete dir="${build}"/>
<delete dir="${dist}"/>
</target>
</project>

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

Flexible

Adaptable

Complicated

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

Demo 1

@SuppressWarnings("serial")
@Entity
@Table(name = "CUSTOMER_INFO")
public class CustomerInfo implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "idSeq")
@SequenceGenerator(name = "idSeq", sequenceName = "CUST_SEQ", allocationSize = 1)
@Column(name = "CUST_ID", nullable = false)
private String customerId;
public void setCustomerId(String customerId) {
this.customerId = customerId;
}
public String getCustomerId() {
return customerId;
}
@Column(name = "EMAIL", nullable = false, length = 128)
private String emailAddress;
public String getEmailAddress() {
return emailAddress;
}
public void setEmailAddress(String emailAddress) {
String oldValue = emailAddress;
this.emailAddress = emailAddress;
firePropertyChangedEvent("emailAddress", oldValue, this.emailAddress);
}

@SuppressWarnings("serial")
@Entity
@Table(name = "CUSTOMER_INFO")
public class CustomerInfo implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "idSeq")
@SequenceGenerator(name = "idSeq", sequenceName = "CUST_SEQ", allocationSize = 1)
@Column(name = "CUST_ID", nullable = false)
private String customerId;
public void setCustomerId(String customerId) {
this.customerId = customerId;
}
public String getCustomerId() {
return customerId;
}
@Column(name = "EMAIL", nullable = false, length = 128)
private String emailAddress;
public String getEmailAddress() {
return emailAddress;
}
public void setEmailAddress(String emailAddress) {
String oldValue = emailAddress;
this.emailAddress = emailAddress;
firePropertyChangedEvent("emailAddress", oldValue, this.emailAddress);
}

entity CustomerInfo
(id=CUST_ID, sequenceName=CUST_SEQ)
{
String emailAddress (notNull, length = 128)
}

entity CustomerInfo
(id=CUST_ID, sequenceName=CUST_SEQ)
{
String emailAddress (notNull, length = 128)
}
Bean
DAO
(POJO)

Underlying Technology

Model
G
ra
m
m
ar

ar
Model
m
m
ra
G
Generator

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

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
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 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
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
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;

grammar org.xtext.example.Entity
with org.eclipse.xtext.common.Terminals Meta model inference
generate entity
"http://www.xtext.org/example/Entity"
entity
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;

Demo 2

Poll "Simple poll"
question "What's your name?" name
question "How do you feel today?" howareyou
() "Fine" fine
() "Great" great
() "Bad" bad
() "Not too bad" not2bad
question "What's your favourite food?" food
[] "Pizza" pizza
[] "Pasta" pasta
[] "Sushi" sushi
[] "Mexican" mexican

Pimp My Write

Tooltips
Scoping
Outline
Label Provider
Validation Hyperlinking / Navigation
AST
Code Formatting
Content Assist
Folding
Quick Fix
Datatype Converter
Parser
Syntax Highlighting

Tooltips
Scoping
Outline
Hyperlinking / Navigation
AST
Code Formatting
Content Assist
Folding
Quick Fix
Datatype Converter
Parser
Syntax Highlighting

Tooltips
Scoping
Outline
Label Provider
Validation Hyperlinking / Navigation
AST
Code Formatting
Content Assist
Folding
Quick Fix
Datatype Converter
Parser
Syntax Highlighting

Conclusion

Abstraction

Use a DSL to develop your tools

Support
Newsgroup
Community Forum
Professional Support

Heiko Sven Moritz Peter Dennis Jan Patrick Sebastian Michael Knut
Behrens Efftinge Eysholdt Friese Hübner Köhnlein Schönbach Zarnekow Clay Wannheden
Individual

Twitter: @xtext
http://www.xtext.org