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Cayenne Object Persistence Framework including all dependencies.
There is a newer version: 1.2.4
/* ====================================================================
*
* The ObjectStyle Group Software License, version 1.1
* ObjectStyle Group - http://objectstyle.org/
* 
* Copyright (c) 2002-2005, Andrei (Andrus) Adamchik and individual authors
* of the software. All rights reserved.
* 
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in
*    the documentation and/or other materials provided with the
*    distribution.
* 
* 3. The end-user documentation included with the redistribution, if any,
*    must include the following acknowlegement:
*    "This product includes software developed by independent contributors
*    and hosted on ObjectStyle Group web site (http://objectstyle.org/)."
*    Alternately, this acknowlegement may appear in the software itself,
*    if and wherever such third-party acknowlegements normally appear.
* 
* 4. The names "ObjectStyle Group" and "Cayenne" must not be used to endorse
*    or promote products derived from this software without prior written
*    permission. For written permission, email
*    "andrus at objectstyle dot org".
* 
* 5. Products derived from this software may not be called "ObjectStyle"
*    or "Cayenne", nor may "ObjectStyle" or "Cayenne" appear in their
*    names without prior written permission.
* 
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED.  IN NO EVENT SHALL THE OBJECTSTYLE GROUP OR
* ITS 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.
* ====================================================================
* 
* This software consists of voluntary contributions made by many
* individuals and hosted on ObjectStyle Group web site.  For more
* information on the ObjectStyle Group, please see
* .
*/
package org.objectstyle.cayenne.dataview;

import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.objectstyle.cayenne.DataObject;

/**
 * @since 1.1
 * @author Andriy Shapochka
 */
public class LookupCache {

    private Map fieldCache = new HashMap();
    private static final Object[] EMPTY_ARRAY = new Object[] {};

    public LookupCache() {
    }

    public void cache(ObjEntityViewField field, List dataObjects) {
        Lookup lookup = getLookup(field);
        if (lookup == null) {
            lookup = new Lookup();
            fieldCache.put(field, lookup);
        }
        lookup.cache(field, dataObjects);
    }

    public void clear() {
        fieldCache.clear();
    }

    public boolean removeFromCache(ObjEntityViewField field) {
        return fieldCache.remove(field) != null;
    }

    public Object[] getCachedValues(ObjEntityViewField field) {
        Lookup lookup = getLookup(field);
        Object[] values = (lookup != null ? lookup.values : EMPTY_ARRAY);
        if (values.length == 0)
            return values;
        else {
            Object[] valuesCopy = new Object[values.length];
            System.arraycopy(values, 0, valuesCopy, 0, values.length);
            return valuesCopy;
        }
    }

    public DataObject getDataObject(ObjEntityViewField field, Object value) {
        Lookup lookup = getLookup(field);
        if (lookup == null)
            return null;
        return lookup.getDataObject(value);
    }

    private Lookup getLookup(ObjEntityViewField field) {
        if (field == null)
            return null;
        return (Lookup) fieldCache.get(field);
    }

    private class Lookup {

        ObjEntityViewField field;
        Object[] values = EMPTY_ARRAY;
        Map valueDataObjectMap;

        void cache(ObjEntityViewField field, List dataObjects) {
            this.field = field;
            if (values.length != dataObjects.size())
                values = new Object[dataObjects.size()];
            valueDataObjectMap = new HashMap(values.length + 1);
            int index = 0;
            for (Iterator i = dataObjects.iterator(); i.hasNext();) {
                DataObject item = (DataObject) i.next();
                values[index] = field.getValue(item);
                valueDataObjectMap.put(values[index], item);
                index++;
            }
        }

        DataObject getDataObject(Object value) {
            return (DataObject) valueDataObjectMap.get(value);
        }
    }
}