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Java > Open Source Codes > org > apache > turbine > modules > screens > RawScreen


1 package org.apache.turbine.modules.screens;
2
3 /*
4  * Copyright 2001-2004 The Apache Software Foundation.
5  *
6  * Licensed under the Apache License, Version 2.0 (the "License")
7  * you may not use this file except in compliance with the License.
8  * You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18
19 // Turbine stuff.
20
21 import org.apache.ecs.ConcreteElement;
22 import org.apache.turbine.modules.Screen;
23 import org.apache.turbine.util.RunData;
24
25 /**
26  * Base class for writing Screens that output binary data. This class
27  * is provided as a helper class for those who want to write Screens
28  * that output raw binary data. For example, it may be extended into
29  * a Screen that outputs a SVG file or a SWF (Flash Player format)
30  * movie. The only thing one has to do is to implement the two
31  * methods <code>getContentType(RunData data)</code> and
32  * <code>doOutput(RunData data)</code> (see below).
33  *
34  * <p> You migth want to take a look at the ImageServer screen class
35  * contained in the TDK.<br>
36  *
37  * @author <a HREF="mailto:rkoenig@chez.com">Regis Koenig</a>
38  * @version $Id: RawScreen.java,v 1.3.2.2 2004/05/20 03:03:54 seade Exp $
39  */
40 public abstract class RawScreen extends Screen
41 {
42     /**
43      * Build the Screen. This method actually makes a call to the
44      * doOutput() method in order to generate the Screen content.
45      *
46      * @param data Turbine information.
47      * @return A ConcreteElement.
48      * @exception Exception, a generic exception.
49      */
50     protected final ConcreteElement doBuild(RunData data)
51             throws Exception JavaDoc
52     {
53         data.getResponse().setContentType(getContentType(data));
54         data.declareDirectResponse();
55         doOutput(data);
56         return null;
57     }
58
59     /**
60      * Set the content type. This method should be overidden to
61      * actually set the real content-type header of the output.
62      *
63      * @param data Turbine information.
64      * @return A String with the content type.
65      */
66     protected abstract String JavaDoc getContentType(RunData data);
67
68     /**
69      * Actually output the dynamic content. The OutputStream can be
70      * accessed like this: <pre>OutputStream out =
71      * data.getResponse().getOutputStream();</pre>.
72      *
73      * @param data Turbine information.
74      * @exception Exception, a generic exception.
75      */
76     protected abstract void doOutput(RunData data)
77             throws Exception JavaDoc;
78
79     /**
80      * The layout must be set to null.
81      *
82      * @param data Turbine information.
83      * @return A null String.
84      */
85     public final String JavaDoc getLayout(RunData data)
86     {
87         return null;
88     }
89 }
90
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