/*******************************************************************************
* Copyright (c) 2007 IBM Corporation 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
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.core.internal.expressions;
import org.w3c.dom.Element;
import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.expressions.EvaluationResult;
import org.eclipse.core.expressions.Expression;
import org.eclipse.core.expressions.ExpressionInfo;
import org.eclipse.core.expressions.IEvaluationContext;
/**
* This class makes use of the <b>org.eclipse.core.expressions.definitions</b>
* extension point to evaluate the current context against pre-defined
* expressions. It provides core expression re-use.
*
* @since 3.3
*/
public class ReferenceExpression extends Expression {
// consider making this a more general extension manager
// for now it's just part of the reference expression
private static DefinitionRegistry fgDefinitionRegistry= null;
private static DefinitionRegistry getDefinitionRegistry() {
if (fgDefinitionRegistry == null) {
fgDefinitionRegistry= new DefinitionRegistry();
}
return fgDefinitionRegistry;
}
private static final String ATT_DEFINITION_ID= "definitionId"; //$NON-NLS-1$
/**
* The seed for the hash code for all equals expressions.
*/
private static final int HASH_INITIAL= ReferenceExpression.class.getName().hashCode();
private String fDefinitionId;
public ReferenceExpression(String definitionId) {
Assert.isNotNull(definitionId);
fDefinitionId= definitionId;
}
public ReferenceExpression(IConfigurationElement element) throws CoreException {
fDefinitionId= element.getAttribute(ATT_DEFINITION_ID);
Expressions.checkAttribute(ATT_DEFINITION_ID, fDefinitionId);
}
public ReferenceExpression(Element element) throws CoreException {
fDefinitionId= element.getAttribute(ATT_DEFINITION_ID);
Expressions.checkAttribute(ATT_DEFINITION_ID, fDefinitionId.length() > 0 ? fDefinitionId : null);
}
public EvaluationResult evaluate(IEvaluationContext context) throws CoreException {
Expression expr= getDefinitionRegistry().getExpression(fDefinitionId);
return expr.evaluate(context);
}
public void collectExpressionInfo(ExpressionInfo info) {
Expression expr;
try {
expr= getDefinitionRegistry().getExpression(fDefinitionId);
} catch (CoreException e) {
// We didn't find the expression definition. So no
// expression info can be collected.
return;
}
expr.collectExpressionInfo(info);
}
public boolean equals(final Object object) {
if (!(object instanceof ReferenceExpression))
return false;
final ReferenceExpression that= (ReferenceExpression)object;
return this.fDefinitionId.equals(that.fDefinitionId);
}
protected int computeHashCode() {
return HASH_INITIAL * HASH_FACTOR + fDefinitionId.hashCode();
}
}