Xbase is a partial programming language implemented in Xtext and is meant to be embedded and xtended within other programming languages and domain-specific languages (DSL) written in Xtext. This presentation provides hooks how to starting learning and using Xbase. Please not that this presentation (date: 2012-11-23) is based on Xtext/Xbase 2.3.1 and thus uses the old API of Xbase.

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Am Beispiel des Domain Model Examples
© itemis AG

2. Agenda
 Xbase
 Anwendungsfälle
 Xbase im Domain Model Example
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 Links
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2

3. Xbase – Am Beispiel des Domain Model Examples
Was ist Xbase?
“Xbase is a partial programming language implemented in Xtext
and is meant to be embedded and xtended within other programming languages
and domain-specific languages (DSL) written in Xtext.”
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Quelle: Sven Efftinge - Xbase - A new programming language?
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3

4. Xbase – Am Beispiel des Domain Model Examples
Generelle Bestandteile von Xbase
Expression-Grammatik
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JVMTypes
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Extensions (Bibliothek von Funktionen, die für Typen bereitgestellt werden)
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Xbase Compiler (zu Java Code) / Xbase Interpreter
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4

5. Xbase – Am Beispiel des Domain Model Examples
Xbase im Detail (1)
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Xbase.xtext
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Typen: Arrays, einfache Typ-Referenzen, Funktionstypen (Lambda-Ausdrücke), parametrisierte TypReferenzen, Java-Primitive -> Xbase implementiert Java Typsystem und ist konform zur Java Lang
Spec
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Expressions (1)
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Literale: String, Nummer (entspricht Integer), Boolean, Null, Typ (entspricht .class)
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Operatoren: fest eingebaute boolsche / arithmetische Operatoren sowie with-Operator für Lambda
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binär: +=, ||, &&, ==, !=, <, >, <=, >=, ->, .., =>, <<, >>, <<<, >>>, <>, ?:, <=>, +, -, *, /, %, **
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unär: !, -
Zuweisungen (Assignments)
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Feature Calls (property access, null safe feature Call, static feature call)
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Constructor Call
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Lambda Ausdrücke (aka Closures): z.B. myList.findFirst([ e | e.name==null ])
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5

6. Xbase – Am Beispiel des Domain Model Examples
Xbase im Detail (2)
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Expressions (ctd.)
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Switch Expression (switch, case)
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Variable Declarations (nur in Blocks erlaubt)
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Blocks, entspricht Container für imperative Code-Sequenzen
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For Loop
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While Loop
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Do-While Loop
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Return Expression
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Throwing Exceptions
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try-catch-finally expression
Implizite Variablen 'this‘ und 'it‘: Referenz auf den aktuellen Kontext, it kann auch innerhalb von
Funktionen verwendet werden
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If Expression (if, else if, else)
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6

7. Xbase – Am Beispiel des Domain Model Examples
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Xbase Extensions
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7

8. Xbase – Am Beispiel des Domain Model Examples
Xbase Compiler
Standard-Generator für Xbase Expressions, der Java-Code generiert
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wie man Xbase erweitert, und was man alles anpassen muss, ist hier beschrieben: Extending Xbase
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Expressions können meist beliebig miteinander und beliebig tief kombiniert und verschachtelt sein: ein
Expressions Compiler sollte unabhängig davon in der Lage sein, validen Code zu generieren
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8

9. Xbase – Am Beispiel des Domain Model Examples
Eigenschaften von Xbase
Runs on the JVM
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Compiles to Java
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Statically Typed
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Full Java Generics
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No built-in types
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Closures
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Type Inference
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Operator Overloading
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Simplicity over Syntactical Flexibility
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Everything is an Expression
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9

10. Xbase – Am Beispiel des Domain Model Examples
Abstrakte Anwendungsfälle
extends
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implements
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invokes
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maps to
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model instances/assigments (with type checks)
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invariants/boolean expressions
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decisions/switch/cases
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calculation
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11. Xbase – Am Beispiel des Domain Model Examples
Konkretere Anwendungsfälle
Integration/Verwebung mit bestehendem Code
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Model-Checks durch Typsystem(e)
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durch Typsystem unterstützte Code-Generierung (Expressions an mehreren Stellen)
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12. Xbase – Am Beispiel des Domain Model Examples
Model inferrer & Type inferrer
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Model inferrer
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JDT Integration
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Transparenz Java/DSL
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Tracing
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Debugging
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Type inferrer
Typisierung von in die DSL eingebauten Expression -> Angabe des erwarteten Rückgabetyps
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12

13. Xbase – Am Beispiel des Domain Model Examples
Model inferrer / Generator / Builder Participant
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Ableiten von (Teil-)Artefakten, die sich weiterhin mit DSL integrieren sollen -> Model inferrer
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Reines Erzeugen von Artefakten, die nichts von der DSL wissen müssen -> Generator
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Ausführungshäufigkeit
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Generator: Beim Speichern der DSL
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Model inferrer: Live beim Editieren der DSL-Datei
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Aufruf-Reihenfolge und Build Abhängigkeiten beachten
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Unterschiedliches Verhalten vom Builder in der IDE und im automatisierten Build -> im
automatisierten Build müssen unter Umständen erst Stubs erzeugt werden, damit zunächst alle
Referenzen aufgelöst werden können und so trotz wechselseitiger Abhängigkeit alle Artefakte
kompiliert werden können
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DSL referenziert auf Java-Elemente, die noch nicht generiert worden sind bzw. zwar schon
generiert wurden aber noch nicht kompiliert worden sind (Java Compiler lief noch nicht)
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13

14. Xbase – Am Beispiel des Domain Model Examples
Wann sollte man Xbase/JVMTypes verwenden, wann nicht?
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sich über die Zielgruppe(n) der DSL klar werden
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sich über die Auswertungsziele der DSL klar werden
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Generatoren/Interpreter, welche Informationen müssen dazu in den DSLs erfasst werden?
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sich über die Chancen und Risiken der Entscheidung klar werden
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Pro
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bekommt vieles Out-Of-The-Box (Standard Editor und Generator/Compiler-Verhalten, Typ-Checks)
Contra
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eine fachliche DSL wird zu technisch
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DSL wird mit Informationen überfrachtet
Ziel-Artefakte: Code, Konfiguration, Dokumentation, Testdaten, Tests, Datenbankskripte,
Buildskripte, ...
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immer dran denken: man kann Xbase auch ohne JVMTypes verwenden, und die Xbase
Expression-Struktur auch ohne den Standard-Xbase-Compiler nutzen
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14

15. Xbase – Am Beispiel des Domain Model Examples
Änderungen durch Xbase
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Grammatik-Definition
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grammar … with org.eclipse.xtext.xbase.Xbase
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import 'http://www.eclipse.org/xtext/common/JavaVMTypes' as types
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 die Sprache muss von Xbase erben
 optional
MWE2 Grammar Generator
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Registrieren der neuen EPackages und GenModels + URI-Mapping
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fragment = types.TypesGeneratorFragment {}
 für JDT Integration u.a. in Proposals
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fragment = xbase.XbaseGeneratorFragment {}
 für ModelInferrer
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public class …ScopeProvider extends XbaseScopeProvider
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class …JvmModelInferrer extends AbstractModelInferrer  für Mapping auf JvmTypes
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public class SprayTypeProvider extends XbaseTypeProvider  Typisieren von Expresssions
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…RuntimeModule: @Override public Class<? extends ITypeProvider> bindITypeProvider() { … }
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Im Scope-Provider localScope definieren für Expressions (it, this)
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 für Scopen der Expressions
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16. Xbase – Am Beispiel des Domain Model Examples
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Xbase in Spray
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17. Xbase – Am Beispiel des Domain Model Examples
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Xbase in Spray
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18. Xbase – Am Beispiel des Domain Model Examples
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19

20. Xbase – Am Beispiel des Domain Model Examples
Erweiterungen für das Domain Model Example
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DSL definieren, um das Mapping zwischen Fachmodell und Persistenz-Modell zu definieren
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Zuweisungen können auch durch Verknüpfungen erfolgen, z.B. Name = Vorname + ” “ + Nachname
•
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dabei müssen durch das Typsystem invalide Zuweisungen erkannt werden bzw. erst gar nicht angeboten
werden
Zuweisungen können Guards enthalten, z.B. Anrede = if(gender == ‘female’) “Frau” else “Herr”
Analog zu Jnario eine Test-Beschreibungs-Sprache definieren, um
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Erwartungen auszudrücken: Wenn Eingabe diese Belegung Dann Ausgabe diese Belegung
Abfrage-Sprache definieren
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Test-Datensätze auszudrücken, also defacto Instanzieren des Domänen-Modells
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21. Xbase – Am Beispiel des Domain Model Examples
Links: Dokumentation & Blogs
Xbase - A new programming language?
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Xbase Language Reference
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Xtext and Java
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Xbase - Implementing domainspecific languages for Java
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Xtext 2.1: using Xbase variables
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The JvmModelInferrer, the debugger and Xbase in Xtext 2.3
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Extending Xbase
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Pragmatic DSL Design with Xtext, Xbase and Xtend 2
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Five simple steps to your JVM language
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Using JVM Types in Xtext 2.1 and the ImportManager
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Xtext casts: Debug-support, Number literals, 7 languages, Jnario
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XREPL
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22. Xbase – Am Beispiel des Domain Model Examples
Links: Xbase Source Code
Xbase.xtext
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JvmModelGenerator.xtend
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XbaseCompiler.java
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XbaseCompiler2.java (benutzt das neue Typsystem)
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AbstractXbaseCompiler.java
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XbaseInterpreter.java
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JvmModelAssociator.java
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JvmTypesBuilder.java
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TypeConvertingCompiler.java
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23. Xbase – Am Beispiel des Domain Model Examples
Links: Xbase nutzende Projekte
Xtend (see Xtend.xtext)
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Sigasi - VHDL editor (closed source)
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openHAB (see Rules.xtext, Script.xtext)
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Spray (see Spray.xtext, Shape.xtext, Style.xtext)
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Jnario (see Spec.xtext)
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Tocea - Architecture-Designer (see QueryDsl.xtext)
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Xsemantics (see Documentation, see Xsemantics.xtext)
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EMF-IncQuery (see PatternLanguage.xtext)
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JST (see Jst.xtext)
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eLang (see EL.xtext)
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MQL (see ModelQueryLanguage.xtext)
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Demonstratoren: Fowlers statemachine with expressions (see MyDsl.xtext), LorenzoBettini - Xtext2
experiments, Meinte Boersma - Xtext2-DSLs
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24. Xbase – Am Beispiel des Domain Model Examples
Links: Domain Model Example
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Example auf dem aktuellen Juno Stand: File -> New -> Other -> Examples/Xtext Examples/Xtext
Domain Model Example
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Example auf dem Indigo-Stand
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Language Workbench Competetion 2011 – Xtext
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Doownload-Sektion mit Screencasts und den Projekt-Stände nach jedem Kapitel
XbaseIntegrationTest.java
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Schritt für Schritt Anleitung (pdf)
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