//tabstop=4
//*****************************************************************************/
// Project: jpl
//
// File:    $Id$
// Date:    $Date$
// Author:  Fred Dushin <fadushin@syr.edu>
//          
//
// Description:
//    
//
// -------------------------------------------------------------------------
// Copyright (c) 1998 Fred Dushin
//                    All rights reserved.
// 
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Library Public License for more details.
//*****************************************************************************/
package jpl;



//----------------------------------------------------------------------/
// QueryInProgressException
/**
 * An exception of this type is thrown if a Query is made while 
 * another Query is in progress, for example, if the JPL programmer
 * has negglected to close a query by exhausting all solutions or by failing
 * to rweind() a Query, or in multi-threaded situations.
 * <p>
 * To prevent this kind of exception from being thrown, first make 
 * absolutely sure that all Queries are being closed properly, either
 * by exhausting all solutions in a Query (i.e., hasMoreSolutions()
 * returns false), or by explicitly calling rewind().  If your program
 * involves multi-threading, make sure you obtain the lock from the
 * Query object before entering a hasMoreSolutions()/nextSolution loop:
 * <pre>
 * Query query = // get a query somehow
 * synchronized ( jpl.Query.lock() ){
 *     while ( query.hasMoreElements() ){
 *          Hashtable solution = query.nextSolution();
 *          // process solution...
 *     }
 * }
 * </pre>
 * <b>Note:</b>  In most situations such care is not necessary, since
 * the Query.query(), Query,oneSolution(), and Query.allSolutions()
 * methods are thread-safe.  However, users may have reason
 * to use the hasMoreSolutions() and nextSolutions() methods, which,
 * while synchronized, do allow Queries to be opened between calls to
 * these methods.
 * <p>
 * If you catch this Exception, you can usese the query() accessor to 
 * obtain a reference to the Query that is in progress.
 * 
 * <hr><i>
 * Copyright (C) 1998  Fred Dushin<p>
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.<p>
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Library Public License for more details.<p>
 * </i><hr>
 * @author  Fred Dushin <fadushin@syr.edu>
 * @version $Revision$
 */
// Implementation notes:  
// 
//----------------------------------------------------------------------/
public final class
QueryInProgressException extends JPLException
{
	private Query query_ = null;
	
	protected 
	QueryInProgressException( Query query )
	{
		super( "QueryInProgressException: Query in progress=" + query.toString() );
		
		this.query_ = query;
	}
	
	/**
	 * @return a reference to the Query that is in progress
	 */
	public final Query
	query()
	{
		return this.query_;
	}
}