Workshop On Xtext

Software Installation
• You‘ll ﬁnd a CD with the required software on your desk

• Unzip the Eclipse distribution matching your OS
Windows users: Use a location close to the root directory

• Run the Eclipse executable

• Choose File -> Import -> Existing projects into workspace

• Select Archive ﬁle and choose workspace.zip from the CD

Workshop
Moritz Eysholdt, Sebastian Zarnekow, Jan Köhnlein

Moritz Eysholdt Jan Köhnlein

Sebastian Zarnekow

What is a
Domain Speciﬁc
Language (DSL)?

A domain-speciﬁc language (DSL)
is a formal, processable language
targeting at a speciﬁc viewpoint or aspect
of a system.

A domain-specific language (DSL)
is a formal, processable language
targeting at a specific viewpoint or aspect
of a system.

Its semantics, flexibility and notation is designed
in order to support working with that viewpoint
as good as possible.

Why would I
want to use a
DSL?

Why isn‘t
everybody using
DSLs?

Isn‘t text a
little bit old-
fashioned?

}

protected String getErrorMessage() {
return errorMessage.toString();
}

Graphics

public boolean isSameStructure(EObject left, EObject right) {
counter = 0;
return internalIsSameStructure(left, right);
}

public boolean internalIsSameStructure(EObject left, EObject right) {
++counter;
if (!isSameClass(left.eClass(), right.eClass())) {
errorMessage.append("Classes are not equal: " + left + " != " + ri
return false;
}
List<EObject> leftChildren = getRelevantChildren(left);
List<EObject> rightChildren = getRelevantChildren(right);
if(leftChildren.size() != rightChildren.size()) {
errorMessage.append("Number of children differs " + left + " " + r
return false;
}
for (int i = 0; i < leftChildren.size(); ++i) {
if(!internalIsSameStructure(leftChildren.get(i), rightChildren.get
errorMessage.append("Children differ " + left + " " + right +
return false;
}
}

Text
return true;
}

protected boolean isSameClass(EClass left, EClass right) {
return left.getName().equals(right.getName())
&& left.getEPackage().getNsURI().equals(right.getEPackage().g
}

protected List<EObject> getRelevantChildren(EObject _this) {
List<EObject> relevantChildren = new ArrayList<EObject>(_this.eContents(
for (Iterator<EObject> i = relevantChildren.iterator(); i.hasNext();) {
EObject next = i.next();
if (!isRelevantChild(_this, next)) {
i.remove();
}
}
return relevantChildren;
}

protected boolean isRelevantChild(EObject container, EObject child) {
return true;

}

}

Graphics

counter = 0;
}

• High-level views

++counter;
return false;
}
return false;
}
return false;
}
}

Text
return true;
}

}

i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


++counter;
return false;
}
return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;

Suggests non-formalism

return false;
}
return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;


return false;
}
return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal
i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;



• Individual tools
return false;
}
return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal
i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;



return false;
}
return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal

• Well established tools
i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;



return false;
}

• Hard to evolve

return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal

i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;



return false;
}

• Hard to evolve

return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal


}

} • Easy to evolve
i.remove();

}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;



return false;
}

• Hard to evolve


• Editing with mouse

}
return false;

return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal


}

i.remove();

}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;



return false;
}

• Hard to evolve


• Editing with mouse

}
return false;

return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal


i.remove();

•
}

} Editing with keyboard

return true;

Showtime !
• In your Eclipse workbench
• Choose Run->Run conﬁgurations...
• Double click on Eclipse Application
• Go to the Arguments tab and add
-XX:MaxPermSize=128m
to the VM arguments
• Click on Run

A Guided Example
entity Conference {
property Name : String
on
Attendees refs many Pers
Sp eakers refs many Speaker
}

entity Person {
property Name : String
}
{
enti ty Speaker extends Person
n
Sessions refs many Sessio
}

entity Session {
property Title: String
property IsTutorial : Bool
}

Grammar Language

grammar org.xtext.cg2009.Entities
with org.eclipse.xtext.common.Terminals

generate entities "http://www.xtext.org/cg2009/Entities"

Model :
(entities += Entity)+;

Entity returns Entity:
'entity' name=ID ('extends' superType=[Entity])? '{'
(properties+=Property)*
'}';

Property:
SimpleProperty | ReferenceProperty;

SimpleProperty:
'property' name=ID ':' type=('String'|'Number'|'Bool');

ReferenceProperty :
name=ID 'refs' ('one' | many?='many')? type=[Entity];

Edit SQL with Xtext
CREATE TABLE Conferences (
id INTEGER NOT NULL PRIMARY KEY,
• Only
)
name CHAR(50)
Create-Statements

• List of columns

Edit SQL with Xtext
CREATE TABLE Conferences (
id INTEGER NOT NULL PRIMARY KEY,
name CHAR(50)

• Enhance with
)

Foreign Keys CREATE TABLE Speaker (
name CHAR(50),
id INTEGER,
FOREIGN KEY (id)
REFERENCES Conference(id)
)

Cross References

Model Element

Cross References

Element Name

Model Element

Cross References

Element Name

resolve

Model Element

Cross References

Element Name

resolve determin

Model Element

Problem:
Names may not be ambiguous.

Problem:

Solution:
Implement a ScopeProvider!

Problem:

Solution:
Implement a ScopeProvider!

A Scope is a context speciﬁc, hierarchical
collection of all reachable model elements
and their respective names.

Scope Provider

Make Foreign Keys work!

public IScope scope_ForeignKey_from(
ForeignKey context, EReference reference) {
Table fromTable = (Table) context.eContainer();
return createTableScope(fromTable);
}

Meta-Model Inference
grammar org.xtext.codeGeneration.Entities
with org.eclipse.xtext.common.Terminals

generate entities "http://www.xtext.org/CG2009/Entities"

Model :
(entities += Entity)+;

Entity returns Entity:
'entity' name=ID ('extends' superType=[Entity])? '{'
(properties+=Property)*
'}';

Property:
SimpleProperty | ReferenceProperty;

SimpleProperty:
'property' name=ID ':' type=('String'|'Number'|'Bool');

ReferenceProperty :
name=ID 'refs' ('one' | many?='many')? type=[Entity];

Model Conferences
with Xtext

How do I create a language
for an existing meta-model?

Model Conferences
with Xtext

Validate Your
Conference
1. Have a look at the generated Validator-Stub.
2. Implement some checks for your language.
3. Check out the results.

@Check
public void checkSpeakersName(Speaker speaker) {
assertTrue("Speaker's name is to short.",
ConferencesLanguagePackage.SPEAKER__NAME,
speaker.getName().length() >= 2);
}

Convention
over
Conﬁguration

Conﬁgured with
Google Guice

class MyDslRuntimeModule extends DefaultRuntimeModule {
Class<? extends ServiceInterface> bindService() {
return MyServiceImplementation.class;
}
}

Extensible Language
Generator
• Generates a lot of Java code
• Composed of fragments
• Customizable
• Add your own
fragments!

Formatting
Pretty Printing
Code Beautiﬁcation

import
<Literature.entities> entity
City {Int id; String
name;}
entity Store { Int
id; String name;
Int
city
references
City.
id; }

Formatting
Pretty Printing
Code Beautiﬁcation

import
name;}
entity Store { Int
id; String name;
Int import <Literature.entities>
city
references entity City {
City. Int id;
id; } String name;
}

entity Store {
Int id;
String name;
Int city references
City.id;
}

Formatting
Pretty Printing Code Beautiﬁcation

import
name;}
entity Store { Int
id; String name;
Int import <Literature.entities>
city
references entity City {
City. Int id;
id; } String name;
}

entity Store {
Int id;
String name;
Int city references
City.id;
§ 1. At ... do ...
}
§ 2. At ... do ...
§ 3. At ... do ...
§ 4. At ... do ...
...

Integration with EMF
eclipse

Any EMF-based modeling
Code Generator GMF Editor P R O J E C T
Component

eclipse

Component

<<abstract>>
XMIResource
Resource

eclipse

Component

<<abstract>> XMI
XMIResource
Resource

eclipse

Component

<<abstract>> XMI
XMIResource
Resource

XtextResource

eclipse

Component

<<abstract>> XMI
XMIResource
Resource

XtextResource Text

eclipse

Component

<<abstract>> XMI
XMIResource
Resource

XtextResource Text

Parser Linker Serializer

ValueConverter ScopeProvider Formatter

EMF Index
• Indexes all resources in workspace
• Query elements and cross-references
• Efﬁcient scoping

EMF Index
• Indexes all resources in workspace
• Query elements and cross-references
• Efﬁcient scoping
Load
Resources

Learn more at
http://www.xtext.org

Workshop On Xtext

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