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Java > Open Source Codes > org > displaytag > tags > TemplateTag


1 /**
2  * Licensed under the Artistic License; you may not use this file
3  * except in compliance with the License.
4  * You may obtain a copy of the License at
5  *
6  * http://displaytag.sourceforge.net/license.html
7  *
8  * THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR
9  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
10  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
11  */
12 package org.displaytag.tags;
13
14 import javax.servlet.jsp.PageContext JavaDoc;
15 import javax.servlet.jsp.tagext.BodyTagSupport JavaDoc;
16
17 import org.displaytag.exception.ObjectLookupException;
18 import org.displaytag.util.LookupUtil;
19
20
21 /**
22  * Base template class.
23  * @author bgsmith
24  * @author Fabrizio Giustina
25  * @version $Revision: 956 $ ($Author: fgiust $)
26  */
27 public abstract class TemplateTag extends BodyTagSupport JavaDoc
28 {
29
30     /**
31      * <p>
32      * evaluate an expression in a way similar to LE in jstl.
33      * </p>
34      * <p>
35      * the first token is supposed to be an object in the page scope (default scope) or one of the following:
36      * </p>
37      * <ul>
38      * <li>pageScope</li>
39      * <li>requestScope</li>
40      * <li>sessionScope</li>
41      * <li>applicationScope</li>
42      * </ul>
43      * <p>
44      * Tokens after the object name are interpreted as javabean properties (accessed through getters), mapped or indexed
45      * properties, using the jakarta common-beans library
46      * </p>
47      * @param expression expression to evaluate
48      * @return Object result
49      * @throws ObjectLookupException if unable to get a bean using the given expression
50      */
51     protected Object JavaDoc evaluateExpression(String JavaDoc expression) throws ObjectLookupException
52     {
53
54         String JavaDoc expressionWithoutScope = expression;
55
56         // default scope = request
57 // this is for compatibility with the previous version, probably default should be PAGE
58 int scope = PageContext.REQUEST_SCOPE;
59
60         if (expression.startsWith("pageScope.")) //$NON-NLS-1$
61 {
62             scope = PageContext.PAGE_SCOPE;
63             expressionWithoutScope = expressionWithoutScope.substring(expressionWithoutScope.indexOf('.') + 1);
64         }
65         else if (expression.startsWith("requestScope.")) //$NON-NLS-1$
66 {
67             scope = PageContext.REQUEST_SCOPE;
68             expressionWithoutScope = expressionWithoutScope.substring(expressionWithoutScope.indexOf('.') + 1);
69
70         }
71         else if (expression.startsWith("sessionScope.")) //$NON-NLS-1$
72 {
73             scope = PageContext.SESSION_SCOPE;
74             expressionWithoutScope = expressionWithoutScope.substring(expressionWithoutScope.indexOf('.') + 1);
75
76         }
77         else if (expression.startsWith("applicationScope.")) //$NON-NLS-1$
78 {
79             scope = PageContext.APPLICATION_SCOPE;
80             expressionWithoutScope = expressionWithoutScope.substring(expressionWithoutScope.indexOf('.') + 1);
81
82         }
83
84         return LookupUtil.getBeanValue(this.pageContext, expressionWithoutScope, scope);
85
86     }
87
88 }
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