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    }