objectkey.java

torque服务器源代码

package org.apache.torque.om;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  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.
 *
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 *    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 acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
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 * 5. Products derived from this software may not be called "Apache",
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 */

import java.io.Serializable;
import org.apache.torque.TorqueException;

/**
 * This class can be used to uniquely identify an object within
 * an application.  There are four subclasses: StringKey, NumberKey,
 * and DateKey, and ComboKey which is a Key made up of a combination
 * ofthe first three.
 *
 * @author <a href="mailto:[e-mail]">John McNally</a>
 * @version $Id: ObjectKey.java,v 1.6 2002/11/26 22:32:55 mpoeschl Exp $
 */
public abstract class ObjectKey implements Serializable, Comparable
{
    /**
     * The underlying key value.
     */
    protected Object key;

    /**
     * Initializes the internal key value to <code>null</code>.
     */
    protected ObjectKey()
    {
        key = null;
    }

    /**
     * Returns the hashcode of the underlying value (key), if key is
     * not null.  Otherwise calls Object.hashCode()
     *
     * @return an <code>int</code> value
     */
    public int hashCode()
    {
        if (key == null)
        {
            return super.hashCode();
        }
        return key.hashCode();
    }

    /**
     * Get the underlying object.
     *
     * @return the underlying object
     */
    public Object getValue()
    {
        return key;
    }

    /**
     * Appends a String representation of the key to a buffer.
     *
     * @param sb a <code>StringBuffer</code>
     */
    public void appendTo(StringBuffer sb)
    {
        sb.append(this.toString());
    }

    /**
     * Implements the compareTo method.
     *
     * @param obj the object to compare to this object
     * @return a numeric comparison of the two values
     */
    public int compareTo(Object obj)
    {
        return toString().compareTo(obj.toString());
    }

    /**
     * Reset the underlying object using a String.
     *
     * @param s a <code>String</code> value
     * @exception TorqueException if an error occurs
     */
    public abstract void setValue(String s) throws TorqueException;
}