Parameter.java

/*
 * Copyright 2005-2008 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.openuap.cms.search.index;

import java.io.ObjectStreamException;
import java.io.Serializable;
import java.io.StreamCorruptedException;
import java.util.HashMap;
import java.util.Map;

/**
 * 
 * <p>
 * 参数.
 * </p>
 * 
 * <p>
 * $Id: Parameter.java 3921 2010-10-26 11:43:49Z orangeforjava $
 * </p>
 * 
 * @author Joseph
 * @version 1.0
 */
public abstract class Parameter implements Serializable {
	static Map allParameters = new HashMap();

	private String name;

	private Parameter() {
		// typesafe enum pattern, no public constructor
	}

	protected Parameter(String name) {
		// typesafe enum pattern, no public constructor
		this.name = name;
		String key = makeKey(name);

		if (allParameters.containsKey(key))
			throw new IllegalArgumentException("Parameter name " + key
					+ " already used!");

		allParameters.put(key, this);
	}

	private String makeKey(String name) {
		return getClass() + " " + name;
	}

	public String toString() {
		return name;
	}

	/**
	 * Resolves the deserialized instance to the local reference for accurate
	 * equals() and == comparisons.
	 * 
	 * @return a reference to Parameter as resolved in the local VM
	 * @throws ObjectStreamException
	 */
	protected Object readResolve() throws ObjectStreamException {
		Object par = allParameters.get(makeKey(name));

		if (par == null)
			throw new StreamCorruptedException("Unknown parameter value: "
					+ name);

		return par;
	}

}