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Java > Open Source Codes > org > apache > turbine > modules > layouts > VelocityXslLayout


1 package org.apache.turbine.modules.layouts;
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 import java.io.StringReader JavaDoc;
20
21 import org.apache.commons.logging.Log;
22 import org.apache.commons.logging.LogFactory;
23
24 import org.apache.ecs.ConcreteElement;
25
26 import org.apache.turbine.TurbineConstants;
27 import org.apache.turbine.modules.Layout;
28 import org.apache.turbine.modules.ScreenLoader;
29 import org.apache.turbine.services.velocity.TurbineVelocity;
30 import org.apache.turbine.services.xslt.TurbineXSLT;
31 import org.apache.turbine.util.RunData;
32 import org.apache.turbine.util.template.TemplateNavigation;
33
34 import org.apache.velocity.context.Context;
35
36 /**
37  * This Layout module allows Velocity XML templates to be used as layouts.
38  * <br><br>
39  * Once the (XML) screen and navigation templates have been inserted into
40  * the layout template the result is transformed with a XSL stylesheet.
41  * The stylesheet (with the same name than the screen template) is loaded
42  * and executed by the XSLT service, so it is important that you correctly
43  * set up your XSLT service. If the named stylsheet does not exist the
44  * default.xsl stylesheet is executed. If default.xsl does not exist
45  * the XML is merely echoed.
46  * <br><br>
47  * Since dynamic content is supposed to be primarily located in
48  * screens and navigations there should be relatively few reasons to
49  * subclass this Layout.
50  *
51  * @author <a HREF="mailto:leon@opticode.co.za">Leon Messerschmidt</a>
52  * @author <a HREF="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
53  * @version $Id: VelocityXslLayout.java,v 1.9.2.2 2004/05/20 03:03:54 seade Exp $
54  */
55 public class VelocityXslLayout extends Layout
56 {
57     /** Logging */
58     private static Log log = LogFactory.getLog(VelocityXslLayout.class);
59
60     /** The prefix for lookup up layout pages */
61     private String JavaDoc prefix = TurbineConstants.LAYOUT_PREFIX + "/";
62
63     /**
64      * Build the layout. Also sets the ContentType and Locale headers
65      * of the HttpServletResponse object.
66      *
67      * @param data Turbine information.
68      * @exception Exception a generic exception.
69      */
70     public void doBuild(RunData data)
71         throws Exception JavaDoc
72     {
73         // Get the context needed by Velocity.
74 Context context = TurbineVelocity.getContext(data);
75
76         data.getResponse().setContentType("text/html");
77
78         String JavaDoc screenName = data.getScreen();
79
80         log.debug("Loading Screen " + screenName);
81
82         // First, generate the screen and put it in the context so
83 // we can grab it the layout template.
84 ConcreteElement results =
85             ScreenLoader.getInstance().eval(data, screenName);
86
87         String JavaDoc returnValue = (results == null) ? "" : results.toString();
88
89         // variable for the screen in the layout template
90 context.put(TurbineConstants.SCREEN_PLACEHOLDER, returnValue);
91
92         // variable to reference the navigation screen in the layout template
93 context.put(TurbineConstants.NAVIGATION_PLACEHOLDER,
94                     new TemplateNavigation(data));
95
96         // Grab the layout template set in the VelocityPage.
97 // If null, then use the default layout template
98 // (done by the TemplateInfo object)
99 String JavaDoc templateName = data.getTemplateInfo().getLayoutTemplate();
100
101         log.debug("Now trying to render layout " + templateName);
102
103         // Now, generate the layout template.
104 String JavaDoc temp = TurbineVelocity.handleRequest(context,
105                 prefix + templateName);
106
107         // Finally we do a transformation and send the result
108 // back to the browser
109 TurbineXSLT.transform(
110             data.getTemplateInfo().getScreenTemplate(),
111                 new StringReader JavaDoc(temp), data.getOut());
112     }
113 }
114
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