1 /*
2 * $Header$
3 * $Revision$
4 * $Date$
5 *
6 * ====================================================================
7 *
8 * Copyright 2000-2002 bob mcwhirter & James Strachan.
9 * All rights reserved.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions are
13 * met:
14 *
15 * * Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 *
18 * * Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 *
22 * * Neither the name of the Jaxen Project nor the names of its
23 * contributors may be used to endorse or promote products derived
24 * from this software without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
27 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
29 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
30 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
31 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
32 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
33 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
34 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
35 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
36 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 *
38 * ====================================================================
39 * This software consists of voluntary contributions made by many
40 * individuals on behalf of the Jaxen Project and was originally
41 * created by bob mcwhirter <bob@werken.com> and
42 * James Strachan <jstrachan@apache.org>. For more information on the
43 * Jaxen Project, please see <http://www.jaxen.org/>.
44 *
45 * $Id$
46 */
47
48
49
50 package org.jaxen.expr;
51
52 import java.io.Serializable;
53 import org.jaxen.Context;
54 import org.jaxen.JaxenException;
55
56
57 /**
58 * Represents an XPath predicate such as <code>[position() = last()]</code>.
59 * This is production 8 and 9 in the
60 * <a href="https://www.w3.org/TR/xpath#NT-Predicate">XPath 1.0 specification</a>:
61 *
62 * <pre> [8] Predicate ::= '[' PredicateExpr ']'
63 * [9] PredicateExpr ::= Expr</pre>
64 *
65 */
66 public interface Predicate extends Serializable
67 {
68 /**
69 * Returns the expression in this predicate.
70 *
71 * @return the expression between the brackets
72 */
73 Expr getExpr();
74
75 /**
76 * Change the expression used by this predicate.
77 *
78 * @param expr the new expression
79 */
80 void setExpr(Expr expr);
81
82 /**
83 * Simplify the expression in this predicate.
84 *
85 * @see Expr#simplify()
86 */
87 void simplify();
88
89 /**
90 * Returns the string form of the predicate,
91 * including the square brackets.
92 *
93 * @return the bracketed form of this predicate
94 */
95 String getText();
96
97 /**
98 * Evaluates this predicate's expression and returns the result.
99 * The result will be a <code>java.lang.Double</code> for expressions that
100 * return a number, a <code>java.lang.String</code> for expressions that
101 * return a string, a <code>java.lang.Boolean</code> for expressions that
102 * return a boolean, and a <code>java.util.List</code> for expressions that
103 * return a node-set. In the latter case, the elements of the list are
104 * the actual objects from the source document model. Copies are not made.
105 *
106 * @param context the context in which the expression is evaluated
107 * @return an object representing the result of the evaluation
108 * @throws JaxenException
109 * @see Expr#evaluate(Context)
110 */
111 Object evaluate(Context context) throws JaxenException;
112
113 }