    001    package org.apache.turbine.pipeline;
    002
    003
    004    /*
    005     * Licensed to the Apache Software Foundation (ASF) under one
    006     * or more contributor license agreements.  See the NOTICE file
    007     * distributed with this work for additional information
    008     * regarding copyright ownership.  The ASF licenses this file
    009     * to you under the Apache License, Version 2.0 (the
    010     * "License"); you may not use this file except in compliance
    011     * with the License.  You may obtain a copy of the License at
    012     *
    013     *   http://www.apache.org/licenses/LICENSE-2.0
    014     *
    015     * Unless required by applicable law or agreed to in writing,
    016     * software distributed under the License is distributed on an
    017     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    018     * KIND, either express or implied.  See the License for the
    019     * specific language governing permissions and limitations
    020     * under the License.
    021     */
    022
    023
    024    import java.io.IOException;
    025
    026    import org.apache.turbine.util.TurbineException;
    027
    028    /**
    029     * <p>A <b>ValveContext</b> is the mechanism by which a Valve can trigger the
    030     * execution of the next Valve in a Pipeline, without having to know anything
    031     * about the internal implementation mechanisms.  An instance of a class
    032     * implementing this interface is passed as a parameter to the
    033     * <code>Valve.invoke()</code> method of each executed Valve.</p>
    034     *
    035     * <p><strong>IMPLEMENTATION NOTE</strong>: It is up to the implementation of
    036     * ValveContext to ensure that simultaneous requests being processed (by
    037     * separate threads) through the same Pipeline do not interfere with each
    038     * other's flow of control.</p>
    039     *
    040     * @author Craig R. McClanahan
    041     * @author Gunnar Rjnning
    042     * @author Peter Donald
    043     * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
    044     * @version $Revision: 615328 $ $Date: 2008-01-25 21:25:05 +0100 (Fr, 25 Jan 2008) $
    045     */
    046    public interface ValveContext
    047    {
    048        /**
    049         * <p>Cause the <code>invoke()</code> method of the next Valve
    050         * that is part of the Pipeline currently being processed (if any)
    051         * to be executed, passing on the specified request and response
    052         * objects plus this <code>ValveContext</code> instance.
    053         * Exceptions thrown by a subsequently executed Valve will be
    054         * passed on to our caller.</p>
    055         *
    056         * <p>If there are no more Valves to be executed, execution of
    057         * this method will result in a no op.</p>
    058         *
    059         * @param data The run-time information, including the servlet
    060         * request and response we are processing.
    061         *
    062         * @exception IOException Thrown by a subsequent Valve.
    063         * @exception TurbineException Thrown by a subsequent Valve.
    064         * @exception TurbineException No further Valves configured in the
    065         * Pipeline currently being processed.
    066         */
    067        public void invokeNext(PipelineData data)
    068            throws IOException, TurbineException;
    069    }