org.eclipse.emf.validation
Class AbstractModelConstraint

java.lang.Object
  org.eclipse.emf.validation.AbstractModelConstraint

public abstract class AbstractModelConstraint
extends Object

Abstract superclass of all constraint implementations provided via the constraintProviders extension point in the plug-in manifest XML whose language is "Java".

The same constraint implementation class may be supplied for multiple constraints (distinguished by their IDs in the extension XML). In such cases, the validation system will only create a single instance of the AbstractModelConstraint, shared by all of the constraint IDs. Therefore, this instance should not cache or otherwise retain any state related to a particular constraint or validation operation. If it is necessary to retain any state, then this information should be indexed by the constraint ID provided by the IValidationContext.getCurrentConstraintId() method of the validation context.

Constructor Summary

AbstractModelConstraint()
Initializes me.

Method Summary

abstract IStatus

validate(IValidationContext ctx) Validates an object in the specified context.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AbstractModelConstraint

public AbstractModelConstraint()

Initializes me.

Method Detail

validate

public abstract IStatus validate(IValidationContext ctx)

Validates an object in the specified context. The target of the validation operation is available from the context object.

Note that it is best to use the IValidationContext.createSuccessStatus() and IValidationContext.createFailureStatus(Object...) methods of the context object to create the status object returned from this method, to ensure that the status object returned is correctly handled by the validation system.

A single constraint implementation may check multiple conditions. In such cases, it can return a multi-status of multiple results created by the overloaded variants of the ConstraintStatus.createStatus(IValidationContext, java.util.Collection, String, Object[]) method. In these cases, also, each resulting status can store a distinct result locus. For example:

     public IStatus validate(IValidationContext ctx) {
         List problems = new java.util.ArrayList();
         
         // check the first condition.  This method adds results to the
         //    ctx's result locus if it finds a problem
         IStatus problem = checkFirstCondition(ctx);
         if (problem != null) problems.add(problem);
         
         // check another condition, involving different objects
         problem = checkSecondCondition(ctx);
         if (problem != null) problems.add(problem);
         
         return problems.isEmpty()? ctx.createSuccessStatus() :
             ConstraintStatus.createMultiStatus(ctx, problems);
     }
     
     private IStatus checkFirstCondition(IValidationContext ctx) {
         EObject target = ctx.getTarget();
         
         Collection problemElements = ...; // collect problem elements
         boolean ok = ... ;  // check the target and some related objects
         
         return ok? null : ConstraintStatus.createStatus(
                 ctx,
                 problemElements,
                 "Problem with {0}",
                 new Object[] {problemElements});
     }
     
     private IStatus checkSecondCondition(IValidationContext ctx) ...
 

Parameters:

ctx - the validation context that provides access to the current constraint evaluation environment. The framework will never pass a null value

Returns:

the status of validation of the target object. The IStatus.getSeverity() of the record is either IStatus.OK to indicate success, or some other value to indicate that validation failed. Must not return null

See Also:

IValidationContext.createSuccessStatus(), IValidationContext.createFailureStatus(Object...), ConstraintStatus.createStatus(IValidationContext, java.util.Collection, String, Object[]), ConstraintStatus.createMultiStatus(IValidationContext, Collection)