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 * The idea of a pipeline is being taken from Catalina
030 * in its entirety :-)
031 *
032 * I would like to take the idea further and implement
033 * Valves instead of hardcoding particular methods
034 * in a pipeline.
035 *
036 * It would be more flexible to specify Valves for
037 * a pipeline in an XML file (we can also rip off the
038 * digester rules from T4) and have invoke() as part
039 * of the interface.
040 *
041 * So a set of Valves would be added to the pipeline
042 * and the pipeline would 'invoke' each valve. In the
043 * case Turbine each Valve would produce some output
044 * to be sent out the pipe. I think with another days
045 * work this can be fully working. The first pipeline
046 * to be fully implemented will the ClassicPipeline
047 * will emulate the Turbine 2.1 way of doing things.
048 *
049 * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
050 * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
051 * @author <a href="mailto:peter@courcoux.biz">Peter Courcoux</a>
052 */
053 public interface Pipeline
054 {
055 /**
056 * Initializes this instance. Called once by the Turbine servlet.
057 */
058 public void initialize()
059 throws Exception;
060
061 /**
062 * <p>Add a new Valve to the end of the pipeline.</p>
063 *
064 * @param valve Valve to be added.
065 *
066 * @exception IllegalStateException If the pipeline has not been
067 * initialized.
068 */
069 public void addValve(Valve valve);
070
071 /**
072 * Return the set of all Valves in the pipeline. If there are no
073 * such Valves, a zero-length array is returned.
074 *
075 * @return An array of valves.
076 */
077 public Valve[] getValves();
078
079 /**
080 * <p>Cause the specified request and response to be processed by
081 * the sequence of Valves associated with this pipeline, until one
082 * of these Valves decides to end the processing.</p>
083 *
084 * <p>The implementation must ensure that multiple simultaneous
085 * requests (on different threads) can be processed through the
086 * same Pipeline without interfering with each other's control
087 * flow.</p>
088 *
089 * @param data The run-time information, including the servlet
090 * request and response we are processing.
091 *
092 * @exception IOException an input/output error occurred.
093 */
094 public void invoke(PipelineData data)
095 throws TurbineException, IOException;
096
097 /**
098 * Remove the specified Valve from the pipeline, if it is found;
099 * otherwise, do nothing.
100 *
101 * @param valve Valve to be removed.
102 */
103 public void removeValve(Valve valve);
104 }