1 package org.apache.turbine.pipeline;
2
3
4 /*
5 * Licensed to the Apache Software Foundation (ASF) under one
6 * or more contributor license agreements. See the NOTICE file
7 * distributed with this work for additional information
8 * regarding copyright ownership. The ASF licenses this file
9 * to you under the Apache License, Version 2.0 (the
10 * "License"); you may not use this file except in compliance
11 * with the License. You may obtain a copy of the License at
12 *
13 * http://www.apache.org/licenses/LICENSE-2.0
14 *
15 * Unless required by applicable law or agreed to in writing,
16 * software distributed under the License is distributed on an
17 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
18 * KIND, either express or implied. See the License for the
19 * specific language governing permissions and limitations
20 * under the License.
21 */
22
23
24 import java.io.IOException;
25
26 import org.apache.turbine.util.TurbineException;
27
28 /**
29 * The idea of a pipeline is being taken from Catalina
30 * in its entirety :-)
31 *
32 * I would like to take the idea further and implement
33 * Valves instead of hardcoding particular methods
34 * in a pipeline.
35 *
36 * It would be more flexible to specify Valves for
37 * a pipeline in an XML file (we can also rip off the
38 * digester rules from T4) and have invoke() as part
39 * of the interface.
40 *
41 * So a set of Valves would be added to the pipeline
42 * and the pipeline would 'invoke' each valve. In the
43 * case Turbine each Valve would produce some output
44 * to be sent out the pipe. I think with another days
45 * work this can be fully working. The first pipeline
46 * to be fully implemented will the ClassicPipeline
47 * will emulate the Turbine 2.1 way of doing things.
48 *
49 * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
50 * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
51 * @author <a href="mailto:peter@courcoux.biz">Peter Courcoux</a>
52 */
53 public interface Pipeline
54 {
55 /**
56 * Initializes this instance. Called once by the Turbine servlet.
57 * @throws Exception if the initialization fails
58 */
59 void initialize()
60 throws Exception;
61
62 /**
63 * <p>Add a new Valve to the end of the pipeline.</p>
64 *
65 * @param valve Valve to be added.
66 *
67 * @throws IllegalStateException If the pipeline has not been
68 * initialized.
69 */
70 void addValve(Valve valve);
71
72 /**
73 * Return the set of all Valves in the pipeline. If there are no
74 * such Valves, a zero-length array is returned.
75 *
76 * @return An array of valves.
77 */
78 Valve[] getValves();
79
80 /**
81 * <p>Cause the specified request and response to be processed by
82 * the sequence of Valves associated with this pipeline, until one
83 * of these Valves decides to end the processing.</p>
84 *
85 * <p>The implementation must ensure that multiple simultaneous
86 * requests (on different threads) can be processed through the
87 * same Pipeline without interfering with each other's control
88 * flow.</p>
89 *
90 * @param pipelineData The run-time information, including the servlet
91 * request and response we are processing.
92 * @throws TurbineException if the invocation fails
93 * @throws IOException an input/output error occurred.
94 */
95 void invoke(PipelineData pipelineData)
96 throws TurbineException, IOException;
97
98 /**
99 * Remove the specified Valve from the pipeline, if it is found;
100 * otherwise, do nothing.
101 *
102 * @param valve Valve to be removed.
103 */
104 void removeValve(Valve valve);
105 }