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/*******************************************************************************
* Copyright (c) 2009, 2010 Cloudsmith Inc. 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:
* Cloudsmith Inc. - initial API and implementation
*******************************************************************************/
package org.eclipse.equinox.p2.ql;
import java.util.ArrayList;
import java.util.Iterator;
import org.eclipse.equinox.internal.p2.metadata.expression.EvaluationContext;
import org.eclipse.equinox.internal.p2.ql.expression.QLFactory;
import org.eclipse.equinox.internal.p2.ql.expression.QLUtil;
import org.eclipse.equinox.p2.metadata.expression.*;
import org.eclipse.equinox.p2.query.IMatchQuery;
import org.eclipse.equinox.p2.query.IQueryResult;
/**
* An IQuery implementation that is based on the p2 query language.
*/
public class QLMatchQuery<T> extends QLQuery<T> implements IMatchQuery<T> {
private final IMatchExpression<T> expression;
private IEvaluationContext context;
/**
* Creates a new query instance with indexed parameters.
* @param instanceClass The class used for filtering elements before calling {@link #isMatch(Object)}
* @param expression The expression that represents the query.
*/
public QLMatchQuery(Class<T> instanceClass, IMatchExpression<T> expression) {
super(instanceClass);
this.expression = expression;
}
/**
* Creates a new query instance with indexed parameters.
* @param instanceClass The class used for filtering elements before calling {@link #isMatch(Object)}
* @param expression The expression that represents the query.
* @param parameters Parameters to use for the query.
*/
public QLMatchQuery(Class<T> instanceClass, String expression, Object... parameters) {
this(instanceClass, ExpressionUtil.getFactory().<T> matchExpression(ExpressionUtil.getParser().parse(expression), parameters));
}
/**
* Checks if the <code>candidate</code> object is an instance of the <code>elementClass</code>
* used by this query. If it is, the result calling {@link IMatchExpression#isMatch(IEvaluationContext, Object)}
* on the contained expression is returned.
* @param candidate The object to test
* @return <code>true</code> if <code>candidate</code> is an instance of the element class and the
* expression match test returns true.
*/
public boolean isMatch(T candidate) {
return elementClass.isInstance(candidate) && expression.isMatch(context, candidate);
}
public void postPerform() {
context = null;
}
public void prePerform() {
//
}
public IQueryResult<T> perform(Iterator<T> iterator) {
if (QLUtil.needsTranslationSupport(expression)) {
IQueryContext<T> queryContext = QL.newQueryContext(iterator);
IExpression translations = QLFactory.TRANSLATIONS;
context = EvaluationContext.create(expression.createContext(), translations);
context.setValue(translations, queryContext.getTranslationSupport(getLocale()));
} else
context = expression.createContext();
prePerform();
try {
ArrayList<T> result = new ArrayList<T>();
while (iterator.hasNext()) {
T candidate = iterator.next();
if (isMatch(candidate))
result.add(candidate);
}
return new QueryResult<T>(result);
} finally {
postPerform();
}
}
}
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