package org.apache.turbine.pipeline;

/* ====================================================================
 * 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.
 *
 * 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 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
 *    "Apache Turbine" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache Turbine", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``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 THE APACHE SOFTWARE FOUNDATION 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import java.io.IOException;

import org.apache.turbine.util.TurbineException;

/**
 * <p>A <b>ValveContext</b> is the mechanism by which a Valve can trigger the
 * execution of the next Valve in a Pipeline, without having to know anything
 * about the internal implementation mechanisms.  An instance of a class
 * implementing this interface is passed as a parameter to the
 * <code>Valve.invoke()</code> method of each executed Valve.</p>
 *
 * <p><strong>IMPLEMENTATION NOTE</strong>: It is up to the implementation of
 * ValveContext to ensure that simultaneous requests being processed (by
 * separate threads) through the same Pipeline do not interfere with each
 * other's flow of control.</p>
 *
 * @author Craig R. McClanahan
 * @author Gunnar Rjnning
 * @author Peter Donald
 * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
 * @version $Revision$ $Date$
 */
public interface ValveContext
{
    /**
     * <p>Cause the <code>invoke()</code> method of the next Valve
     * that is part of the Pipeline currently being processed (if any)
     * to be executed, passing on the specified request and response
     * objects plus this <code>ValveContext</code> instance.
     * Exceptions thrown by a subsequently executed Valve will be
     * passed on to our caller.</p>
     *
     * <p>If there are no more Valves to be executed, execution of
     * this method will result in a no op.</p>
     *
     * @param data The run-time information, including the servlet
     * request and response we are processing.
     *
     * @exception IOException Thrown by a subsequent Valve.
     * @exception TurbineException Thrown by a subsequent Valve.
     * @exception TurbineException No further Valves configured in the
     * Pipeline currently being processed.
     */
    public void invokeNext(PipelineData data)
        throws IOException, TurbineException;
}