idkeycomparator.java

实现了Jms的服务器源码,支持多种适配器,DB,FTP,支持多种数据库

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 * ("Software"), with or without modification, are permitted provided
 * that the following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright
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 *    copy of this document.
 *
 * 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 name "Exolab" must not be used to endorse or promote
 *    products derived from this Software without prior written
 *    permission of Exoffice Technologies.  For written permission,
 *    please contact [e-mail].
 *
 * 4. Products derived from this Software may not be called "Exolab"
 *    nor may "Exolab" appear in their names without prior written
 *    permission of Exoffice Technologies. Exolab is a registered
 *    trademark of Exoffice Technologies.
 *
 * 5. Due credit should be given to the Exolab Project
 *    (http://www.exolab.org/).
 *
 * THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
 * ``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
 * EXOFFICE TECHNOLOGIES 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.
 *
 * Copyright 2000 (C) Exoffice Technologies Inc. All Rights Reserved.
 *
 * $Id: IdKeyComparator.java,v 1.4 2003/08/17 01:32:25 tanderson Exp $
 *
 * Date         Author  Changes
 * $Date	    jimm    Created
 */


package org.exolab.jms.persistence;

import java.io.Serializable;
import java.util.Comparator;

import javax.jms.JMSException;


/**
 * A comparator class that iplements a string comparison.
 *
 *
 * <P>Note this class assumes that id's are in some sort of order, such that
 * an earlier generated id is less than a later generated id.
 *
 * @version     $Revision: 1.4 $ $Date: 2003/08/17 01:32:25 $
 * @author      <a href="mailto:[e-mail]">Jim Mourikis</a>
 */
public class IdKeyComparator implements Comparator, Serializable {

    // All Message ID's are prefixed with "ID:"
    private static final int PREFIX_LENGTH = 3;

    /**
     * Default constructor does nothing.
     *
     */
    public IdKeyComparator() {

    }


    /**
     * Implements the compare operator.
     * Compares its two arguments for order. Returns a negative integer, zero,
     * or a positive integer as the first argument is less than, equal to,
     * or greater than the second.
     *
     * @param Object object 1 to compare
     * @param Object object 2 ro compare to.
     * @return int returns -1, 0, 1 if the first argument is less than,
     *		   equal to, or greater than the second.
     * @exception ClassCastException if object types are unknown
     *
     */
    public int compare(Object o1, Object o2)
        throws ClassCastException, NullPointerException {
        int status = 0;

        if (o1 == null && o2 == null)
            status = 0;
        else if (o1 == null)
            status = -1;
        else if (o2 == null)
            status = 1;
        else if (o1 instanceof String &&
            o2 instanceof String) {
            String t1 = (String) o1;
            String t2 = (String) o2;
            try {
                long l1 = strip(t1);
                long l2 = strip(t2);

                if (l1 == l2)
                    status = 0;
                else if (l1 < l2)
                    status = -1;
                else
                    status = 1;
            } catch (NumberFormatException err) {
                System.err.println("Invalid IDs " + t1 + ", " + t2);
            }
        } else {
            throw new ClassCastException("Unknown Object");
        }
        return status;
    }


    /**
     * Indicates whether some other object is "equal to" this Comparator.
     * This method must obey the general contract of Object.equals(Object).
     *
     * @param Object the object to compare to
     * @return boolean true iff objects are equal
     *
     */
    public boolean equals(Object ob) {
        boolean status = false;

        if (ob instanceof IdKeyComparator) status = true;

        return status;
    }


    /**
     * Strip the "ID:" prefix from the string, and return the long number
     * remaininng.
     *
     * @param st The string to strip.
     * @return long the remaing long integer.
     *
     */
    private long strip(String st) throws NumberFormatException {
        return Long.parseLong(st.substring(PREFIX_LENGTH));
    }
} // End IdKeyComparator