1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
3 *
4 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
5 *
6 * Portions Copyright Apache Software Foundation.
7 *
8 * The contents of this file are subject to the terms of either the GNU
9 * 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.
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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
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23 * [name of copyright owner]"
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27 * If you wish your version of this file to be governed by only the CDDL or
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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
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37 */
38
39 package javax.servlet.jsp.el;
40
41 import javax.servlet;
42 import javax.servlet.jsp;
43 import javax.servlet.jsp.tagext;
44 import java.util.Map;
45
46 /**
47 * <p>The abstract class for a prepared expression.</p>
48 *
49 * <p>An instance of an Expression can be obtained via from an
50 * ExpressionEvaluator instance.</p>
51 *
52 * <p>An Expression may or not have done a syntactic parse of the expression.
53 * A client invoking the evaluate() method should be ready for the case
54 * where ELParseException exceptions are raised. </p>
55 *
56 * @since 2.0
57 */
58 public abstract class Expression {
59
60 /**
61 * Evaluates an expression that was previously prepared. In some
62 * implementations preparing an expression involves full syntactic
63 * validation, but others may not do so. Evaluating the expression may
64 * raise an ELParseException as well as other ELExceptions due to
65 * run-time evaluation.
66 *
67 * @param vResolver A VariableResolver instance that can be used at
68 * runtime to resolve the name of implicit objects into Objects.
69 * @return The result of the expression evaluation.
70 *
71 * @exception ELException Thrown if the expression evaluation failed.
72 */
73 public abstract Object evaluate( VariableResolver vResolver )
74 throws ELException;
75 }
76
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