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'databene commons' is an open source Java library by Volker Bergmann.
It provides extensions to the Java core library by utility classes, abstract concepts
and concrete implementations.
/*
* Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
* All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.databene.commons.accessor;
import org.databene.commons.Accessor;
import java.util.List;
import java.util.ArrayList;
/**
* Accessor implementation that caches the value it retrieves first
* until it is manually invalidated.
* Created: 11.03.2006 17:02:27
* @author Volker Bergmann
* @param the object type to access
* @param the type of the value to get from the object
*/
public class AccessorCache implements DependentAccessor {
private String name;
private Accessor realAccessor;
private V cachedValue;
private boolean valid;
public AccessorCache(String name, Accessor realAccessor) {
this.realAccessor = realAccessor;
this.name = name;
this.valid = false;
}
// properties ------------------------------------------------------------------------------------------------------
public String getName() {
return name;
}
public boolean isValid() {
return valid;
}
public void invalidate() {
valid = false;
}
// DependentAccessor interface -------------------------------------------------------------------------------------
@Override
public V getValue(C item) {
if (!valid) {
cachedValue = realAccessor.getValue(item);
valid = true;
}
return cachedValue;
}
@Override
@SuppressWarnings({ "unchecked", "rawtypes" })
public List> getDependencies() {
if (realAccessor instanceof DependentAccessor)
return ((DependentAccessor) realAccessor).getDependencies();
else
return new ArrayList();
}
}