/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
 * [name of copyright owner]"
 * 
 * Contributor(s):
 * 
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */


package javax.jms;

import java.util.Enumeration;

/** A client uses a <CODE>QueueBrowser</CODE> object to look at messages on a 
  * queue without removing them.
  *
  * <P>The <CODE>getEnumeration</CODE> method returns a 
  * <CODE>java.util.Enumeration</CODE> that is used to scan 
  * the queue's messages. It may be an enumeration of the entire content of a 
  * queue, or it may contain only the messages matching a message selector.
  *
  * <P>Messages may be arriving and expiring while the scan is done. The JMS API
  * does 
  * not require the content of an enumeration to be a static snapshot of queue 
  * content. Whether these changes are visible or not depends on the JMS 
  * provider.
  *
  *<P>A <CODE>QueueBrowser</CODE> can be created from either a 
  * <CODE>Session</CODE> or a <CODE> QueueSession</CODE>. 
  *
  * @version     1.1 April 9, 2002
  * @author      Mark Hapner
  * @author      Rich Burridge
  * @author      Kate Stout
  *
  *  @see         javax.jms.Session#createBrowser
  * @see         javax.jms.QueueSession#createBrowser
  * @see         javax.jms.QueueReceiver
  */

public interface QueueBrowser {

    /** Gets the queue associated with this queue browser.
      * 
      * @return the queue
      *  
      * @exception JMSException if the JMS provider fails to get the
      *                         queue associated with this browser
      *                         due to some internal error.
      */

    Queue 
    getQueue() throws JMSException;


    /** Gets this queue browser's message selector expression.
      *  
      * @return this queue browser's message selector, or null if no
      *         message selector exists for the message consumer (that is, if 
      *         the message selector was not set or was set to null or the 
      *         empty string)
      *
      * @exception JMSException if the JMS provider fails to get the
      *                         message selector for this browser
      *                         due to some internal error.
      */

    String
    getMessageSelector() throws JMSException;


    /** Gets an enumeration for browsing the current queue messages in the
      * order they would be received.
      *
      * @return an enumeration for browsing the messages
      *  
      * @exception JMSException if the JMS provider fails to get the
      *                         enumeration for this browser
      *                         due to some internal error.
      */

    Enumeration 
    getEnumeration() throws JMSException;


    /** Closes the <CODE>QueueBrowser</CODE>.
      *
      * <P>Since a provider may allocate some resources on behalf of a 
      * QueueBrowser outside the Java virtual machine, clients should close them
      * when they 
      * are not needed. Relying on garbage collection to eventually reclaim 
      * these resources may not be timely enough.
      *
      * @exception JMSException if the JMS provider fails to close this
      *                         browser due to some internal error.
      */

    void 
    close() throws JMSException;
}