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Xtext and more

Xtext and more.

Articles on Eclipse Xtext by Christian Dietrich

Customizing Xtext Metamodel Inference using Xtend2

July 22, 2011 · Christian Dietrich · Tags: Inference , Metamodel , PostProcessor , Xtend , Xtext

Xtext has nice metamodel inference capabilities. But sometimes you have to do some customizations to the generated ecore metamodel, e.g. adding a derived operation. You have basically two options: (1) move to a manually maintained metamodel (2) use Customized Post Processing as described here http://www.eclipse.org/Xtext/documentation/2_0_0/020-grammar-language.php#customPostProcessing

The second possibility uses good old Xpand/Xtend1 extensions to do the postprocessing. But what if i want to use Xtend2 for that? A very simple solution i’d like to show in this post.

So lets start with the gramar

grammar org.xtext.example.mydsl.MyDsl with org.eclipse.xtext.common.Terminals
 
generate myDsl "http://www.xtext.org/example/mydsl/MyDsl"
 
Model:
    persons+=Person*
;
 
Person:
    "person" firstname=STRING lastname=STRING
;

We now want to add a getFullname Operation to our person. Xtext offers the Interface IXtext2EcorePostProcessor for the postprocessing. So we write a Xtend class for that

package org.xtext.example.mydsl
 
import org.eclipse.xtext.xtext.ecoreInference.IXtext2EcorePostProcessor
import org.eclipse.xtext.GeneratedMetamodel
import org.eclipse.emf.ecore.EPackage
import org.eclipse.emf.ecore.EClassifier
import org.eclipse.emf.ecore.EClass
import org.eclipse.emf.ecore.EcoreFactory
import org.eclipse.emf.ecore.EcorePackage
import org.eclipse.emf.ecore.EcorePackage.Literals
import org.eclipse.emf.codegen.ecore.genmodel.GenModelPackage
import org.eclipse.emf.common.util.BasicEMap$Entry
import org.eclipse.emf.ecore.impl.EStringToStringMapEntryImpl
 
class MyXtext2EcorePostProcessor implements IXtext2EcorePostProcessor {
     
    override void process(GeneratedMetamodel metamodel) {
        metamodel.EPackage.process
    }
     
    def process(EPackage p) {
        for (c : p.EClassifiers.filter(typeof(EClass))) {
            if (c.name == "Person") {
                c.handle
            }
        }
    }
     
    def handle (EClass c) {
        val op = EcoreFactory::eINSTANCE.createEOperation
        op.name = "getFullName"
        op.EType = EcorePackage::eINSTANCE.EString
        val body = EcoreFactory::eINSTANCE.createEAnnotation
        body.source = GenModelPackage::eNS_URI
        val map = EcoreFactory::eINSTANCE.create(EcorePackage::eINSTANCE.getEStringToStringMapEntry()) as BasicEMap$Entry<String,String>
        map.key = "body"
        map.value = "return getFirstname() + \" \" + getLastname();"
        body.details.add(map)
        op.EAnnotations += body
        c.EOperations += op
    }
     
}

The last Problem left is how to make the Generator use this class. Xtext does not offer a explicit place to change the IXtext2EcorePostProcessor. Its default Implementation is bound in the XtextRuntimeModule, that is instantiated in the org.eclipse.xtext.generator.Generator class. so we have to subclass the Generator to get it changed

package org.xtext.example.mydsl;
 
import org.eclipse.xtext.XtextRuntimeModule;
import org.eclipse.xtext.XtextStandaloneSetup;
import org.eclipse.xtext.generator.Generator;
import org.eclipse.xtext.xtext.ecoreInference.IXtext2EcorePostProcessor;
 
import com.google.inject.Guice;
import com.google.inject.Injector;
 
@SuppressWarnings("restriction")
public class ExtendedGenerator extends Generator {
     
    public ExtendedGenerator() {
        new XtextStandaloneSetup() {
            @Override
            public Injector createInjector() {
                return Guice.createInjector(new XtextRuntimeModule() {
                    @Override
                    public Class<? extends IXtext2EcorePostProcessor> bindIXtext2EcorePostProcessor() {
                        return MyXtext2EcorePostProcessor.class;
                    }
                });
            }
        }.createInjectorAndDoEMFRegistration();
    }
 
}

finally we use the in the Generator Workflow

Workflow {
    bean = StandaloneSetup {
        scanClassPath = true
        platformUri = "${runtimeProject}/.."
    }
 
    component = DirectoryCleaner {
        directory = "${runtimeProject}/src-gen"
    }
 
    component = DirectoryCleaner {
        directory = "${runtimeProject}.ui/src-gen"
    }
 
    component = ExtendedGenerator {
        pathRtProject = runtimeProject
        pathUiProject = "${runtimeProject}.ui"
        pathTestProject = "${runtimeProject}.tests"
        projectNameRt = projectName
        projectNameUi = "${projectName}.ui"
        language = {
....

as a result our person has the getFullname Operation

public interface Person extends EObject
{
 
  String getFirstname();
 
 
  void setFirstname(String value);
 
 
  String getLastname();
 
 
  void setLastname(String value);
 
 
  String getFullName();
 
} // Person

public class PersonImpl extends MinimalEObjectImpl.Container implements Person
{
  
  /**
   * <!-- begin-user-doc -->
   * <!-- end-user-doc -->
   * @generated
   */
  public String getFullName()
  {
    return getFirstname() + " " + getLastname();
  }
 
 
 
} //PersonImpl

Xtext 2.0 and UML

July 17, 2011 · Christian Dietrich · Tags: IResource Service Provider , UML , Xtext

Consider you have some (Eclipse) UML2 models and now want to reference e.g. Classes from these model from your dsl. In this blog post i want to show a simple example what to do. We have to do two things: Provide an IResourceServiceProvider for .uml resources and reference the UML class from the grammar. So first we write the grammar. that is quite easy

grammar org.xtext.example.umldsl.UmlDsl with org.eclipse.xtext.common.Terminals
 
import "http://www.eclipse.org/uml2/3.0.0/UML" as uml
import "http://www.eclipse.org/emf/2002/Ecore" as ecore
 
generate umlDsl "http://www.xtext.org/example/umldsl/UmlDsl"
 
Model:
    elements+=Element*
;
 
Element:
    "element" name=ID "mapsTo" ref=[uml::Class|FQN]
;
 
FQN returns ecore::EString:
    ID ("." ID)*
;

Then we have to add some stuff to the Language workflow to get the stuff running

module org.xtext.example.umldsl.GenerateUmlDsl
 
import org.eclipse.emf.mwe.utils.*
import org.eclipse.xtext.generator.*
import org.eclipse.xtext.ui.generator.*
 
var grammarURI = "classpath:/org/xtext/example/umldsl/UmlDsl.xtext"
var file.extensions = "umldsl"
var projectName = "org.xtext.example.umldsl"
var runtimeProject = "../${projectName}"
 
Workflow {
    bean = StandaloneSetup {
        scanClassPath = true
        platformUri = "${runtimeProject}/.."
        uriMap = {
            from = "platform:/plugin/org.eclipse.emf.codegen.ecore/model/GenModel.genmodel"
            to = "platform:/resource/org.eclipse.emf.codegen.ecore/model/GenModel.genmodel"
        }
        uriMap = {
            from = "platform:/plugin/org.eclipse.emf.ecore/model/Ecore.genmodel"
            to = "platform:/resource/org.eclipse.emf.ecore/model/Ecore.genmodel"
        }
        uriMap = {
            from = "platform:/plugin/org.eclipse.uml2.codegen.ecore/model/GenModel.genmodel"
            to = "platform:/resource/org.eclipse.uml2.codegen.ecore/model/GenModel.genmodel"
        }
        uriMap = {
            from = "platform:/plugin/org.eclipse.uml2.uml/model/UML.genmodel"
            to = "platform:/resource/org.eclipse.uml2.uml/model/UML.genmodel"
        }
        uriMap = {
            from = "platform:/plugin/org.eclipse.emf.codegen.ecore/model/GenModel.ecore"
            to = "platform:/resource/org.eclipse.emf.codegen.ecore/model/GenModel.ecore"
        }
        uriMap = {
            from = "platform:/plugin/org.eclipse.emf.ecore/model/Ecore.ecore"
            to = "platform:/resource/org.eclipse.emf.ecore/model/Ecore.ecore"
        }
        uriMap = {
            from = "platform:/plugin/org.eclipse.uml2.codegen.ecore/model/GenModel.ecore"
            to = "platform:/resource/org.eclipse.uml2.codegen.ecore/model/GenModel.ecore"
        }
        uriMap = {
            from = "platform:/plugin/org.eclipse.uml2.uml/model/UML.ecore"
            to = "platform:/resource/org.eclipse.uml2.uml/model/UML.ecore"
        }
        //
        registerGeneratedEPackage = "org.eclipse.emf.ecore.EcorePackage"
        registerGeneratedEPackage = "org.eclipse.uml2.uml.UMLPackage"
        registerGeneratedEPackage = "org.eclipse.emf.codegen.ecore.genmodel.GenModelPackage"
        registerGeneratedEPackage = "org.eclipse.uml2.codegen.ecore.genmodel.GenModelPackage"
        registerGenModelFile = "platform:/resource/org.eclipse.emf.ecore/model/Ecore.genmodel"
        registerGenModelFile = "platform:/resource/org.eclipse.emf.codegen.ecore/model/GenModel.genmodel"
        registerGenModelFile = "platform:/resource/org.eclipse.uml2.uml/model/UML.genmodel"
        registerGenModelFile = "platform:/resource/org.eclipse.uml2.codegen.ecore/model/GenModel.genmodel"
 
    }
 
    ...
}

We add some extra deps to the manifest

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: org.xtext.example.umldsl
Bundle-Vendor: My Company
Bundle-Version: 1.0.0
Bundle-SymbolicName: org.xtext.example.umldsl; singleton:=true
Bundle-ActivationPolicy: lazy
Require-Bundle: org.eclipse.xtext;bundle-version="2.0.0";visibility:=reexport,
 org.apache.log4j;bundle-version="1.2.15";visibility:=reexport,
 org.apache.commons.logging;bundle-version="1.0.4";resolution:=optional;visibility:=reexport,
 org.eclipse.xtext.generator;resolution:=optional,
 org.eclipse.emf.codegen.ecore;resolution:=optional,
 org.eclipse.emf.mwe.utils;resolution:=optional,
 org.eclipse.emf.mwe2.launch;resolution:=optional,
 org.eclipse.uml2.uml;bundle-version="3.2.0",
 org.eclipse.xtext.util,
 org.eclipse.emf.ecore,
 org.eclipse.emf.common,
 org.antlr.runtime,
 org.eclipse.xtext.common.types,
 org.eclipse.uml2.codegen.ecore;bundle-version="1.7.0"
Import-Package: org.apache.log4j,
 org.apache.commons.logging,
 org.eclipse.xtext.xbase.lib,
 org.eclipse.xtext.xtend2.lib
Bundle-RequiredExecutionEnvironment: J2SE-1.5
Export-Package: org.xtext.example.umldsl,
 org.xtext.example.umldsl.services,
 org.xtext.example.umldsl.umlDsl,
 org.xtext.example.umldsl.umlDsl.impl,
 org.xtext.example.umldsl.umlDsl.util,
 org.xtext.example.umldsl.serializer,
 org.xtext.example.umldsl.parser.antlr,
 org.xtext.example.umldsl.parser.antlr.internal,
 org.xtext.example.umldsl.validation

and generate the Language. If we now run a runtime application and create a .uml file and a .umlmodel file we see nothing since the uml stuff is not yet referenceable

UML Not Working

So the second with we create is a IResourceServiceProvider . Therefore we take the plugins org.eclipse.xtext.ecore and org.eclipse.xtext.ui.ecore? , that do the same for .ecorefiles, as inspiration. So we create the pluginsorg.eclipse.xtext.umlandorg.eclipse.xtext.ui.uml` with following content:

UML Plugin

TheUmlResourceDescriptionStrategy customizes the creation of IEObjectDescriptions. This is the stuff that Xtext puts into the index and maps a Name to an EObject or Proxy. In our case we simply subclass from the default and do no further customizations.

package org.eclipse.xtext.uml;
 
import org.eclipse.xtext.resource.impl.DefaultResourceDescriptionStrategy;
 
public class UmlResourceDescriptionStrategy extends DefaultResourceDescriptionStrategy {
 
}

The UmlQualifiedNameProvider gives our UML Stuff a fully qualified name – we take the defaults here too

package org.eclipse.xtext.uml;
 
import org.eclipse.xtext.naming.DefaultDeclarativeQualifiedNameProvider;
 
public class UmlQualifiedNameProvider extends DefaultDeclarativeQualifiedNameProvider {
 
}

Then we have to create a Guice Module to Glue the stuff

package org.eclipse.xtext.uml;
 
import org.eclipse.xtext.naming.IQualifiedNameProvider;
import org.eclipse.xtext.resource.IDefaultResourceDescriptionStrategy;
import org.eclipse.xtext.resource.generic.AbstractGenericResourceRuntimeModule;
 
public class UmlRuntimeModule extends AbstractGenericResourceRuntimeModule {
 
    @Override
    protected String getLanguageName() {
        return "org.eclipse.uml2.uml.editor.presentation.UMLEditorID";
    }
 
    @Override
    protected String getFileExtensions() {
        return "uml";
    }
 
    public Class<? extends IDefaultResourceDescriptionStrategy> bindIDefaultResourceDescriptionStrategy() {
        return UmlResourceDescriptionStrategy.class;
    }
 
    @Override
    public Class<? extends IQualifiedNameProvider> bindIQualifiedNameProvider() {
        return UmlQualifiedNameProvider.class;
    }
 
}

If we want to use this stuff from an mwe(2) workflow we have to create a Support-Class for this too

package org.eclipse.xtext.uml;
 
import org.eclipse.xtext.resource.generic.AbstractGenericResourceSupport;
 
import com.google.inject.Module;
 
public class UmlSupport extends AbstractGenericResourceSupport {
 
    @Override
    protected Module createGuiceModule() {
        return new UmlRuntimeModule();
    }
 
}

Finally we add some stuff to the manifest and we’re done with the runtime stuf

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: Uml
Bundle-SymbolicName: org.eclipse.xtext.uml
Bundle-Version: 1.0.0.qualifier
Bundle-RequiredExecutionEnvironment: JavaSE-1.6
Require-Bundle: org.eclipse.xtext;bundle-version="2.0.0",
 org.eclipse.uml2.uml;bundle-version="3.2.0"
Export-Package: org.eclipse.xtext.uml

UML UI Plugin

Then we have to do some stuff at the ui side too. We create some glue code (Activator, ExecutableExtensionFactory (to be able to use guice in the plugin.xml) and an UiModule)

/*******************************************************************************
 * Copyright (c) 2010 itemis AG (http://www.itemis.eu) and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *******************************************************************************/
package org.eclipse.xtext.ui.uml;
 
import org.apache.log4j.Logger;
import org.eclipse.ui.plugin.AbstractUIPlugin;
import org.eclipse.xtext.ui.shared.SharedStateModule;
import org.eclipse.xtext.uml.UmlRuntimeModule;
import org.osgi.framework.BundleContext;
 
import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.util.Modules;
 
/**
 * The activator class controls the plug-in life cycle
 */
public class Activator extends AbstractUIPlugin {
 
    private static final Logger logger = Logger.getLogger(Activator.class);
 
    // The plug-in ID
    public static final String PLUGIN_ID = "org.eclipse.xtext.ui.uml"; //$NON-NLS-1$
 
    // The shared instance
    private static Activator plugin;
 
    private Injector injector;
 
    /**
     * The constructor
     */
    public Activator() {
    }
 
    public Injector getInjector() {
        return injector;
    }
 
    private void initializeEcoreInjector() {
        injector = Guice.createInjector(
                Modules.override(Modules.override(new UmlRuntimeModule())
                .with(new UmlUiModule(plugin)))
                .with(new SharedStateModule()));
    }
 
    @Override
    public void start(BundleContext context) throws Exception {
        super.start(context);
        plugin = this;
        try {
            initializeEcoreInjector();
        } catch(Exception e) {
            logger.error(e.getMessage(), e);
            throw e;
        }
    }
 
    @Override
    public void stop(BundleContext context) throws Exception {
        plugin = null;
        injector = null;
        super.stop(context);
    }
 
    /**
     * Returns the shared instance
     *
     * @return the shared instance
     */
    public static Activator getDefault() {
        return plugin;
    }
 
}

/*******************************************************************************
 * Copyright (c) 2010 itemis AG (http://www.itemis.eu) and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *******************************************************************************/
package org.eclipse.xtext.ui.uml;
 
import org.eclipse.ui.plugin.AbstractUIPlugin;
import org.eclipse.xtext.ui.LanguageSpecific;
import org.eclipse.xtext.ui.editor.IURIEditorOpener;
import org.eclipse.xtext.ui.resource.generic.EmfUiModule;
 
public class UmlUiModule extends EmfUiModule {
 
    public UmlUiModule(AbstractUIPlugin plugin) {
        super(plugin);
    }
 
    @Override
    public void configureLanguageSpecificURIEditorOpener(com.google.inject.Binder binder) {
        binder.bind(IURIEditorOpener.class).annotatedWith(LanguageSpecific.class).to(UmlEditorOpener.class);
    }
 
}

/*******************************************************************************
 * Copyright (c) 2010 itemis AG (http://www.itemis.eu) and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *******************************************************************************/
package org.eclipse.xtext.ui.uml;
 
import org.eclipse.xtext.ui.guice.AbstractGuiceAwareExecutableExtensionFactory;
import org.osgi.framework.Bundle;
 
import com.google.inject.Injector;
 
public class ExecutableExtensionFactory extends AbstractGuiceAwareExecutableExtensionFactory {
 
    @Override
    protected Bundle getBundle() {
        return Activator.getDefault().getBundle();
    }
 
    @Override
    protected Injector getInjector() {
        return Activator.getDefault().getInjector();
    }
 
}

Of course we want to UML Editor to open smoothly if we click on an element referenced from UML too so we create an LanguageSpecificURIEditorOpener too

/*******************************************************************************
 * Copyright (c) 2010 itemis AG (http://www.itemis.eu) and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *******************************************************************************/
package org.eclipse.xtext.ui.uml;
 
import java.util.Collections;
 
import org.eclipse.emf.common.util.URI;
import org.eclipse.emf.ecore.EObject;
import org.eclipse.emf.ecore.EReference;
import org.eclipse.ui.IEditorPart;
import org.eclipse.xtext.ui.editor.LanguageSpecificURIEditorOpener;
import org.eclipse.uml2.uml.editor.presentation.UMLEditor;
 
public class UmlEditorOpener extends LanguageSpecificURIEditorOpener {
 
    @Override
    protected void selectAndReveal(IEditorPart openEditor, URI uri,
            EReference crossReference, int indexInList, boolean select) {
        UMLEditor umlEditor = (UMLEditor) openEditor.getAdapter(UMLEditor.class);
        if (umlEditor != null) {
            EObject eObject = umlEditor.getEditingDomain().getResourceSet().getEObject(uri, true);
            umlEditor.setSelectionToViewer(Collections.singletonList(eObject));
        }
    }
 
}

we add some deps to the manifest

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: Uml
Bundle-SymbolicName: org.eclipse.xtext.ui.uml;singleton:=true
Bundle-Version: 1.0.0.qualifier
Bundle-RequiredExecutionEnvironment: JavaSE-1.6
Require-Bundle: org.eclipse.uml2.uml.editor;bundle-version="3.1.100",
 org.eclipse.xtext.uml;bundle-version="1.0.0",
 org.eclipse.xtext.ui;bundle-version="2.0.0",
 org.eclipse.xtext.ui.shared;bundle-version="2.0.0"
Import-Package: org.apache.log4j;version="1.2.15"
Bundle-Activator: org.eclipse.xtext.ui.uml.Activator
Bundle-ActivationPolicy: lazy

And finally register our resource service provider to the extension point Xtext offers for that.

<?xml version="1.0" encoding="UTF-8"?>
<?eclipse version="3.4"?>
<plugin>
     
    <extension
          point="org.eclipse.xtext.extension_resourceServiceProvider">
        <resourceServiceProvider
              class="org.eclipse.xtext.ui.uml.ExecutableExtensionFactory:org.eclipse.xtext.ui.resource.generic.EmfResourceUIServiceProvider"
              uriExtension="uml">
        </resourceServiceProvider>
    </extension>
  
</plugin>

We restart our runtime application, and TATATATA: it works 😉

UML Working

the source code can be found at https://github.com/cdietrich/xtext-uml-example

IQualifiedNameProviders in Xtext 2.0

July 16, 2011 · Christian Dietrich · Tags: IQualifiedNameProvider , Xtext

Xtext 2.0 come with a change to the IQualifiedNameProvider interface. This interface is used to calculate a name for EObjects. The Name is used in Xtext’s index, for cross referencing and much more.

public interface IQualifiedNameProvider extends Function<EObject, QualifiedName> {
 
    QualifiedName getFullyQualifiedName(EObject obj);
 
}

Here we see the API change: There is a rename of the getQualifiedName method to getFullyQualifedName. In Xtext 1.0.x the qualified name was a simple String, now it is a wrapper class that holds the segements of the qualified name.

There are two default implementations for a IQualifiedNameProvider: SimpleNameProvider and DefaultDeclarativeQualifiedNameProvider. Consider we have a grammar like

grammar org.xtext.example.mydsl.MyDsl with org.eclipse.xtext.common.Terminals
 
generate myDsl "http://www.xtext.org/example/mydsl/MyDsl"
 
Package:
    "package" name=ID "{"
        elements+=Element*
    "}"
;
 
Element:
    "element" name=ID
;

and a sample model like

package TestPackage {
    element A
    element B
}

Then with SimpleNameProvider we would have following qualified names.

  • TestPackage for the package
  • A and B for the elements

And with DefaultDeclarativeQualifiedNameProvider we would have following qualified names.

  • TestPackage for the package
  • TestPackage.A and TestPackage.B for the elements

Both Providers take the name EAttribute of our Package and Element to do the calculation. The DefaultDeclarativeQualifiedNameProvider uses the Elements parents qualified name too. (a fully qualified name ;-)) But it won’t work e.g. if our grammar would look like

grammar org.xtext.example.mydsl.MyDsl with org.eclipse.xtext.common.Terminals
 
generate myDsl "http://www.xtext.org/example/mydsl/MyDsl"
 
Package:
    "package" name=ID "{"
        elements+=Element*
    "}"
;
 
Element:
    "element" id=ID
;

with Element having and id and not a name. We can easily change this by creating and binding our own IQualifiedNameProvider e.g. by extending DefaultDeclarativeQualifiedNameProvider

package org.xtext.example.mydsl;
 
import org.eclipse.xtext.naming.DefaultDeclarativeQualifiedNameProvider;
import org.eclipse.xtext.naming.QualifiedName;
import org.xtext.example.mydsl.myDsl.Element;
import org.xtext.example.mydsl.myDsl.Package;
 
public class MyDslQNP extends DefaultDeclarativeQualifiedNameProvider{
 
    QualifiedName qualifiedName(Element e) {
        Package p = (Package) e.eContainer();
        return QualifiedName.create(p.getName(), e.getId());
    }
 
}

We simply write a method qualifiedName that is called from the polymorpthic dispatcher when calculating the name of an Element

package org.xtext.example.mydsl;
 
import org.eclipse.xtext.naming.IQualifiedNameProvider;
 
/**
 * Use this class to register components to be used at runtime / without the Equinox extension registry.
 */
public class MyDslRuntimeModule extends org.xtext.example.mydsl.AbstractMyDslRuntimeModule {
 
    @Override
    public Class<? extends IQualifiedNameProvider> bindIQualifiedNameProvider() {
        return MyDslQNP.class;
    }
 
}

Hover support in Xtext 2.0: Tutorial

July 16, 2011 · Christian Dietrich · Tags: Hover , Xtext

Xtext 2.0 comes with an all new Hover API (see Christoph’s Blog http://ckulla.wordpress.com/2011/02/06/hover-support-in-xtext-2-0/). I want to give a short introduction on how to use what with Xtext’s Greeting Example.

So first we create a new Xtext project with the wizard and generate the language. We start a runtime application and create a project with a model file. Here is what the default hover looks like:

Default Hover

We want is to adopt the hover support to look like this:

Custom Hover

We have to basically implement 2 interfaces: IEObjectHoverProvider to customize the header line and IEObjectDocumentationProvider to customize the content section. Here 2 simple implementations (using appropriate superclasses)

package org.xtext.example.mydsl.ui;
 
import org.eclipse.emf.ecore.EObject;
import org.eclipse.xtext.ui.editor.hover.html.DefaultEObjectHoverProvider;
import org.xtext.example.mydsl.myDsl.Greeting;
 
public class MyDslEObjectHoverProvider extends DefaultEObjectHoverProvider {
 
    @Override
    protected String getFirstLine(EObject o) {
        if (o instanceof Greeting) {
            return "Damn good greeting: " + ((Greeting)o).getName();
        }
        return super.getFirstLine(o);
    }
 
}

package org.xtext.example.mydsl.ui;
 
import org.eclipse.emf.ecore.EObject;
import org.eclipse.xtext.documentation.IEObjectDocumentationProvider;
import org.xtext.example.mydsl.myDsl.Greeting;
 
public class MyDslEObjectDocumentationProvider implements IEObjectDocumentationProvider {
 
    @Override
    public String getDocumentation(EObject o) {
        if (o instanceof Greeting) {
            return "This is a nice Greeting with nice <b>markup</b> in the <i>documentation</i>";
        }
        return null;
    }
 
}

Finally we have to bind these classes in the UiModule of our dsl.

package org.xtext.example.mydsl.ui;
 
import org.eclipse.ui.plugin.AbstractUIPlugin;
import org.eclipse.xtext.documentation.IEObjectDocumentationProvider;
import org.eclipse.xtext.ui.editor.hover.IEObjectHoverProvider;
 
/**
 * Use this class to register components to be used within the IDE.
 */
public class MyDslUiModule extends org.xtext.example.mydsl.ui.AbstractMyDslUiModule {
    public MyDslUiModule(AbstractUIPlugin plugin) {
        super(plugin);
    }
 
    public Class<? extends IEObjectHoverProvider> bindIEObjectHoverProvider() {
        return MyDslEObjectHoverProvider.class;
    }
 
    public Class<? extends IEObjectDocumentationProvider> bindIEObjectDocumentationProviderr() {
        return MyDslEObjectDocumentationProvider.class;
    }
}

That is all we have to do to get customized hovers with Xtext 2.0.