/*
* (c) Copyright 2009 by Volker Bergmann. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, is permitted under the terms of the
* GNU General Public License (GPL).
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* WITHOUT A WARRANTY OF ANY KIND. ALL EXPRESS OR IMPLIED CONDITIONS,
* REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE
* HEREBY EXCLUDED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
package org.databene.benerator.engine.expression;
import org.databene.commons.Context;
import org.databene.script.Expression;
import org.databene.script.expression.ExpressionProxy;
/**
* Caches the result of another expression and returns it on subsequent calls
* without evaluating the other expression again. The cache can be invalidated
* by calling the <code>invalidate()</code> method.<br/><br/>
* Created: 21.10.2009 14:42:15
* @since 0.6.0
* @author Volker Bergmann
*/
public class CachedExpression<E> extends ExpressionProxy<E> {
private boolean valid;
private E cachedValue;
public CachedExpression(Expression<E> realExpression) {
super(realExpression);
this.cachedValue = null;
this.valid = false;
}
@Override
public E evaluate(Context context) {
if (!valid) {
cachedValue = super.evaluate(context);
valid = true;
}
return cachedValue;
}
public void invalidate() {
valid = false;
}
}