CacheKey.java

/*
 *    Copyright 2009-2014 the original author or authors.
 *
 *    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.apache.ibatis.cache;

import java.io.Serializable;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.List;

/**
 * @author Clinton Begin
 */
public class CacheKey implements Cloneable, Serializable {

	private static final long serialVersionUID = 1146682552656046210L;

	public static final CacheKey NULL_CACHE_KEY = new NullCacheKey();

	private static final int DEFAULT_MULTIPLYER = 37;
	private static final int DEFAULT_HASHCODE = 17;

	private int multiplier;
	private int hashcode;
	private long checksum;
	private int count;
	private List<Object> updateList;

	public CacheKey() {
		this.hashcode = DEFAULT_HASHCODE;
		this.multiplier = DEFAULT_MULTIPLYER;
		this.count = 0;
		this.updateList = new ArrayList<Object>();
	}

	public CacheKey(Object[] objects) {
		this();
		updateAll(objects);
	}

	public int getUpdateCount() {
		return updateList.size();
	}

	public void update(Object object) {
		if (object != null && object.getClass().isArray()) {
			int length = Array.getLength(object);
			for (int i = 0; i < length; i++) {
				Object element = Array.get(object, i);
				doUpdate(element);
			}
		} else {
			doUpdate(object);
		}
	}

	private void doUpdate(Object object) {
		int baseHashCode = object == null ? 1 : object.hashCode();

		count++;
		checksum += baseHashCode;
		baseHashCode *= count;

		hashcode = multiplier * hashcode + baseHashCode;

		updateList.add(object);
	}

	public void updateAll(Object[] objects) {
		for (Object o : objects) {
			update(o);
		}
	}

	public boolean equals(Object object) {
		if (this == object)
			return true;
		if (!(object instanceof CacheKey))
			return false;

		final CacheKey cacheKey = (CacheKey) object;

		if (hashcode != cacheKey.hashcode)
			return false;
		if (checksum != cacheKey.checksum)
			return false;
		if (count != cacheKey.count)
			return false;

		for (int i = 0; i < updateList.size(); i++) {
			Object thisObject = updateList.get(i);
			Object thatObject = cacheKey.updateList.get(i);
			if (thisObject == null) {
				if (thatObject != null)
					return false;
			} else {
				if (!thisObject.equals(thatObject))
					return false;
			}
		}
		return true;
	}

	public int hashCode() {
		return hashcode;
	}

	public String toString() {
		StringBuilder returnValue = new StringBuilder().append(hashcode)
				.append(':').append(checksum);
		for (int i = 0; i < updateList.size(); i++) {
			returnValue.append(':').append(updateList.get(i));
		}

		return returnValue.toString();
	}

	@Override
	public CacheKey clone() throws CloneNotSupportedException {
		CacheKey clonedCacheKey = (CacheKey) super.clone();
		clonedCacheKey.updateList = new ArrayList<Object>(updateList);
		return clonedCacheKey;
	}

}