01: /*
02: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
03: *
04: * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
05: *
06: * Portions Copyright Apache Software Foundation.
07: *
08: * The contents of this file are subject to the terms of either the GNU
09: * General Public License Version 2 only ("GPL") or the Common Development
10: * and Distribution License("CDDL") (collectively, the "License"). You
11: * may not use this file except in compliance with the License. You can obtain
12: * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
13: * or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
14: * language governing permissions and limitations under the License.
15: *
16: * When distributing the software, include this License Header Notice in each
17: * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
18: * Sun designates this particular file as subject to the "Classpath" exception
19: * as provided by Sun in the GPL Version 2 section of the License file that
20: * accompanied this code. If applicable, add the following below the License
21: * Header, with the fields enclosed by brackets [] replaced by your own
22: * identifying information: "Portions Copyrighted [year]
23: * [name of copyright owner]"
24: *
25: * Contributor(s):
26: *
27: * If you wish your version of this file to be governed by only the CDDL or
28: * only the GPL Version 2, indicate your decision by adding "[Contributor]
29: * elects to include this software in this distribution under the [CDDL or GPL
30: * Version 2] license." If you don't indicate a single choice of license, a
31: * recipient has the option to distribute your version of this file under
32: * either the CDDL, the GPL Version 2 or to extend the choice of license to
33: * its licensees as provided above. However, if you add GPL Version 2 code
34: * and therefore, elected the GPL Version 2 license, then the option applies
35: * only if the new code is made subject to such option by the copyright
36: * holder.
37: */
38:
39: package org.apache.taglibs.standard.tag.el.core;
40:
41: import javax.servlet.jsp.JspException;
42: import javax.servlet.jsp.PageContext;
43: import javax.servlet.jsp.tagext.Tag;
44:
45: import org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager;
46: import org.apache.taglibs.standard.tag.common.core.NullAttributeException;
47:
48: /**
49: * <p>Contains some static utilities to facilitate common forms of
50: * expression evaluation.</p>
51: *
52: * @author Shawn Bayern
53: */
54:
55: public class ExpressionUtil {
56:
57: /** Evaluates an expression if present, but does not allow the expression
58: * to evaluate to 'null', throwing a NullAttributeException if it
59: * does. The function <b>can</b> return null, however, if the
60: * expression itself is null.
61: */
62: public static Object evalNotNull(String tagName,
63: String attributeName, String expression,
64: Class expectedType, Tag tag, PageContext pageContext)
65: throws JspException {
66: if (expression != null) {
67: Object r = ExpressionEvaluatorManager.evaluate(
68: attributeName, expression, expectedType, tag,
69: pageContext);
70: if (r == null)
71: throw new NullAttributeException(tagName, attributeName);
72: return r;
73: } else
74: return null;
75: }
76: }
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