EVL-EMF Validation Integration¶

The Eclipse Modeling Framework (EMF) provides an extensible model validation service via the EValidator API. The API allows contributing additional validators for Ecore metamodels via the EValidator.Registry class. In this way, you can provide additional validation constraints for metamodels that will be invoked when models conforming to these metamodels are validated by EMF (e.g. through the Model → Right-click → Validate menu in EMF's built-in reflective).

The EvlValidator Class¶

Epsilon provides an implementation of EMF's EValidator interface (EvlValidator) that can execute EVL constraints against EMF models.

Registering EVL Constraints¶

There are two ways to register your EVL constraints for an Ecore metamodel (EPackage): programmatically or via an extension point.

Programmatically¶

For this you need to create a new instance of an EvlValidator and then add it to the EValidatorRegistry. Note that if there are existing validators registered for the metamodel, you should not remove/overwrite them; instead you should combine them in a CompositeEValidator.

The following snippet outlines the general idea (you need to make your own provisions if you need to validate multiple EPackages with the same validator (e.g. use the EvlValidator#addAdditionalPackage method)).

// Assuming you have generated the metamodel code
EPackage ePackage = YourPackage.eINSTANCE;

// Pass a model name if your script uses it
// Pass a valid bundle ID as it used for reporting (if not in a plugin use your project name or similar)
EvlValidator evlValidator = new EvlValidator(
    evlScriptURI, modelName, ePackage.nsUri(), bundleId);

EValidator existingValidator = EValidator.Registry.INSTANCE.getEValidator(ePackage);
if (existingValidator instanceof CompositeEValidator) {
    ((CompositeEValidator) existingValidator).getDelegates().add(evlValidator);
} else {
    if (existingValidator == null) {
        existingValidator = EObjectValidator.INSTANCE;
    }
    CompositeEValidator newValidator = new CompositeEValidator();
    newValidator.getDelegates().add(existingValidator);
    newValidator.getDelegates().add(evlValidator);
    EValidator.Registry.INSTANCE.put(ePackage, newValidator);
}

Via the Extension Point¶

Epsilon provides the org.eclipse.epsilon.evl.emf.validation extension point for registering EVL constraints against EPackages in Eclipse. The extension point will handle the EvlValidator instantiation and registration for you.

<plugin>
   ...
   <extension
         point="org.eclipse.epsilon.evl.emf.validation">
      <constraintsBinding
            compose="true"
            constraints="src/test.evl"
            namespaceURI="http://your.package.uri"
            validator="my.project.evl.EvlExtendedValidator">
            <additionalNamespaceURI
               namespaceURI="http://some.other.pacakge.uri">
         </additionalNamespaceURI>
      </constraintsBinding>
   </extension>
</plugin>

We recommend setting the compose attribute to true, else you will overwrite existing validators. You can also specify additional metamodels to be accessed by this validator using the additionalNamespaceURI entries. Note that you can also provide your own validator implementation. If omitted, the default EvlValidator will be used (should be sufficient for most cases).

Runtime Adjustments¶

Note

The following adjustments are only possible if you control invocation of the validation, i.e. you are calling it programatically and not via the EMF/Eclipse right-click menu.

There are three important runtime aspects to be taken into consideration when using the EVL-EMF integration.

Error Dialogs¶

Within Eclipse, Epsilon reports errors via Eclipse's JFace MessageDialog API. This is appropriate when checking constraints via the Model → Right-click → Validate menu in EMF's built-in tree-based editor, but can be cumbersome when the validation is integrated into other parts of your UI. To disable error reporting via message dialogs you can use use the EvlValidator#setShowErrorDialog function. You can either call this on you instance or override the isShowErrorDialog() if you extend the EvlValidator class.

Logging¶

Epsilon logs errors in the console. As with the dialogs, this can be enabled/disabled. For this, you can use use the EvlValidator#setLogErrors method. Similarly, the isLogErrors() can be overridden.

Tip

The dialogs are part of the logging, so disabling logging will disable the dialogs too.

Validation progress and cancellation¶

Within Eclipse it is important to allow uses to cancel a running validation. To do so, we need to pass an IProgressMonitor to the EvlValidator. For this, you need to provide your own Diagnostician.

public class MyDiagnostician extends Diagnostician {

    public Diagnostic validate(EObject eObject, IProgressMonitor monitor) {
        BasicDiagnostic diagnostics = createDefaultDiagnostic(eObject);
        validate(eObject, diagnostics, createDefaultContext(monitor), monitor);
        return diagnostics;
    }

    // Overload the Diagnostician implementation to inject the monitor into the context
    public Map<Object, Object> createDefaultContext(IProgressMonitor monitor) {
        final Map<Object, Object> defaultContext = super.createDefaultContext();
        defaultContext.put(EvlValidator.VALIDATION_MONITOR, monitor);
        return defaultContext;
    }
}

And then in your code (e.g. command handler):

@Override
public void run(IProgressMonitor monitor) throws CoreException {
    myDgnstc = new MyDiagnostician();
    Diagnostic dgnstc = rnblDgnstc.validate(model.getContents().get(0), monitor);
    ...

The extended diagnostician can also be used to configure any EvlValidators provided via extension points, e.g. to disable logging or dialogs. In this case we assume that all EvlValidators are within CompositeEValidators (adjust if not using them). This implementation uses a brute force approach; ideally you should search for a specific EPackage instead.

public class MyDiagnostician extends Diagnostician {

    public MyDiagnostician() {
        super();
        for(Object validator : eValidatorRegistry.values()) {
            if (validator instanceof CompositeEValidator) {
                CompositeEValidator cmpsVal = (CompositeEValidator) validator;
                findEvlValidators(cmpsVal);
            }
        }
    }

    public Diagnostic validate(EObject eObject, IProgressMonitor monitor) {
        BasicDiagnostic diagnostics = createDefaultDiagnostic(eObject);
        validate(eObject, diagnostics, createDefaultContext(monitor), monitor);
        return diagnostics;
    }

    // Overload the Diagnostician implementation to inject the monitor into the context
    public Map<Object, Object> createDefaultContext(IProgressMonitor monitor) {
        final Map<Object, Object> defaultContext = super.createDefaultContext();
        defaultContext.put(EvlValidator.VALIDATION_MONITOR, monitor);
        return defaultContext;
    }

    /**
     * Find all {@link EVlValidator}s and configure them.
     * @param cmpsVal
     * @return
     */
    private void findEvlValidators(CompositeEValidator cmpsVal) {
        for (EValidator nstdVal : cmpsVal.getDelegates()) {
            if (nstdVal instanceof EVlValidator) {
                EVlValidator evlVal = (EVlValidator) nstdVal;
                evlVal.setShowErrorDialog(false);
                // Other settings or hook error listeners
                // evlVal.addValidationProblemListener(this);
            }
        }
    }
}