1 package org.apache.turbine.modules.screens;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22
23 // Turbine stuff.
24
25 import org.apache.turbine.modules.Screen;
26 import org.apache.turbine.pipeline.PipelineData;
27 import org.apache.turbine.util.RunData;
28
29 /**
30 * Base class for writing Screens that output binary data. This class
31 * is provided as a helper class for those who want to write Screens
32 * that output raw binary data. For example, it may be extended into
33 * a Screen that outputs a SVG file or a SWF (Flash Player format)
34 * movie. The only thing one has to do is to implement the two
35 * methods <code>getContentType(PipelineData data)</code> and
36 * <code>doOutput(PipelineData data)</code> (see below).
37 *
38 * <p> You might want to take a look at the ImageServer screen class
39 * contained in the TDK.<br>
40 *
41 * @author <a href="mailto:rkoenig@chez.com">Regis Koenig</a>
42 * @author <a href="mailto:peter@courcoux.biz">Peter Courcoux</a>
43 * @version $Id$
44 */
45 public abstract class RawScreen implements Screen
46 {
47 /**
48 * Build the Screen. This method actually makes a call to the
49 * doOutput() method in order to generate the Screen content.
50 *
51 * @param pipelineData Turbine information.
52 * @return A ConcreteElement.
53 * @throws Exception a generic exception.
54 */
55 @Override
56 public final String doBuild(PipelineData pipelineData)
57 throws Exception
58 {
59 RunData data = pipelineData.getRunData();
60 data.getResponse().setContentType(getContentType(pipelineData));
61 data.declareDirectResponse();
62 doOutput(pipelineData);
63 return null;
64 }
65
66 /**
67 * Set the content type. This method should be overridden to
68 * actually set the real content-type header of the output.
69 *
70 * @param pipelineData Turbine information.
71 * @return A String with the content type.
72 */
73 protected abstract String getContentType(PipelineData pipelineData);
74
75 /**
76 * Actually output the dynamic content. The OutputStream can be
77 * accessed like this: <pre>OutputStream out =
78 * data.getResponse().getOutputStream();</pre>.
79 *
80 * @param pipelineData Turbine information.
81 * @throws Exception a generic exception.
82 */
83 protected abstract void doOutput(PipelineData pipelineData) throws Exception;
84
85 /**
86 * The layout must be set to null.
87 *
88 * @param pipelineData Turbine information.
89 * @return A null String.
90 */
91 @Override
92 public final String getLayout(PipelineData pipelineData)
93 {
94 return null;
95 }
96 }