1 /*
2 * Copyright (c) 2003, 2005, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.xml.xpath;
27
28 import org.xml.sax.InputSource;
29 import javax.xml.namespace.QName;
30
31 /**
32 * <p><code>XPathExpression</code> provides access to compiled XPath expressions.</p>
33 *
34 * <a name="XPathExpression-evaluation"/>
35 * <table border="1" cellpadding="2">
36 * <thead>
37 * <tr>
38 * <th colspan="2">Evaluation of XPath Expressions.</th>
39 * </tr>
40 * </thead>
41 * <tbody>
42 * <tr>
43 * <td>context</td>
44 * <td>
45 * If a request is made to evaluate the expression in the absence
46 * of a context item, an empty document node will be used for the context.
47 * For the purposes of evaluating XPath expressions, a DocumentFragment
48 * is treated like a Document node.
49 * </td>
50 * </tr>
51 * <tr>
52 * <td>variables</td>
53 * <td>
54 * If the expression contains a variable reference, its value will be found through the {@link XPathVariableResolver}.
55 * An {@link XPathExpressionException} is raised if the variable resolver is undefined or
56 * the resolver returns <code>null</code> for the variable.
57 * The value of a variable must be immutable through the course of any single evaluation.</p>
58 * </td>
59 * </tr>
60 * <tr>
61 * <td>functions</td>
62 * <td>
63 * If the expression contains a function reference, the function will be found through the {@link XPathFunctionResolver}.
64 * An {@link XPathExpressionException} is raised if the function resolver is undefined or
65 * the function resolver returns <code>null</code> for the function.</p>
66 * </td>
67 * </tr>
68 * <tr>
69 * <td>QNames</td>
70 * <td>
71 * QNames in the expression are resolved against the XPath namespace context.
72 * </td>
73 * </tr>
74 * <tr>
75 * <td>result</td>
76 * <td>
77 * This result of evaluating an expression is converted to an instance of the desired return type.
78 * Valid return types are defined in {@link XPathConstants}.
79 * Conversion to the return type follows XPath conversion rules.</p>
80 * </td>
81 * </tr>
82 * </table>
83 *
84 * <p>An XPath expression is not thread-safe and not reentrant.
85 * In other words, it is the application's responsibility to make
86 * sure that one {@link XPathExpression} object is not used from
87 * more than one thread at any given time, and while the <code>evaluate</code>
88 * method is invoked, applications may not recursively call
89 * the <code>evaluate</code> method.
90 * <p>
91 *
92 * @author <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>
93 * @author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
94 * @see <a href="http://www.w3.org/TR/xpath#section-Expressions">XML Path Language (XPath) Version 1.0, Expressions</a>
95 * @since 1.5
96 */
97 public interface XPathExpression {
98
99 /**
100 * <p>Evaluate the compiled XPath expression in the specified context and return the result as the specified type.</p>
101 *
102 * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
103 * variable, function and QName resolution and return type conversion.</p>
104 *
105 * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants},
106 * then an <code>IllegalArgumentException</code> is thrown.</p>
107 *
108 * <p>If a <code>null</code> value is provided for
109 * <code>item</code>, an empty document will be used for the
110 * context.
111 * If <code>returnType</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
112 *
113 * @param item The starting context (a node, for example).
114 * @param returnType The desired return type.
115 *
116 * @return The <code>Object</code> that is the result of evaluating the expression and converting the result to
117 * <code>returnType</code>.
118 *
119 * @throws XPathExpressionException If the expression cannot be evaluated.
120 * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
121 * @throws NullPointerException If <code>returnType</code> is <code>null</code>.
122 */
123 public Object evaluate(Object item, QName returnType)
124 throws XPathExpressionException;
125
126 /**
127 * <p>Evaluate the compiled XPath expression in the specified context and return the result as a <code>String</code>.</p>
128 *
129 * <p>This method calls {@link #evaluate(Object item, QName returnType)} with a <code>returnType</code> of
130 * {@link XPathConstants#STRING}.</p>
131 *
132 * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
133 * variable, function and QName resolution and return type conversion.</p>
134 *
135 * <p>If a <code>null</code> value is provided for
136 * <code>item</code>, an empty document will be used for the
137 * context.
138 *
139 * @param item The starting context (a node, for example).
140 *
141 * @return The <code>String</code> that is the result of evaluating the expression and converting the result to a
142 * <code>String</code>.
143 *
144 * @throws XPathExpressionException If the expression cannot be evaluated.
145 */
146 public String evaluate(Object item)
147 throws XPathExpressionException;
148
149 /**
150 * <p>Evaluate the compiled XPath expression in the context of the specified <code>InputSource</code> and return the result as the
151 * specified type.</p>
152 *
153 * <p>This method builds a data model for the {@link InputSource} and calls
154 * {@link #evaluate(Object item, QName returnType)} on the resulting document object.</p>
155 *
156 * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
157 * variable, function and QName resolution and return type conversion.</p>
158 *
159 * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants},
160 * then an <code>IllegalArgumentException</code> is thrown.</p>
161 *
162 * <p>If <code>source</code> or <code>returnType</code> is <code>null</code>,
163 * then a <code>NullPointerException</code> is thrown.</p>
164 *
165 * @param source The <code>InputSource</code> of the document to evaluate over.
166 * @param returnType The desired return type.
167 *
168 * @return The <code>Object</code> that is the result of evaluating the expression and converting the result to
169 * <code>returnType</code>.
170 *
171 * @throws XPathExpressionException If the expression cannot be evaluated.
172 * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
173 * @throws NullPointerException If <code>source</code> or <code>returnType</code> is <code>null</code>.
174 */
175 public Object evaluate(InputSource source, QName returnType)
176 throws XPathExpressionException;
177
178 /**
179 * <p>Evaluate the compiled XPath expression in the context of the specified <code>InputSource</code> and return the result as a
180 * <code>String</code>.</p>
181 *
182 * <p>This method calls {@link #evaluate(InputSource source, QName returnType)} with a <code>returnType</code> of
183 * {@link XPathConstants#STRING}.</p>
184 *
185 * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
186 * variable, function and QName resolution and return type conversion.</p>
187 *
188 * <p>If <code>source</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
189 *
190 * @param source The <code>InputSource</code> of the document to evaluate over.
191 *
192 * @return The <code>String</code> that is the result of evaluating the expression and converting the result to a
193 * <code>String</code>.
194 *
195 * @throws XPathExpressionException If the expression cannot be evaluated.
196 * @throws NullPointerException If <code>source</code> is <code>null</code>.
197 */
198 public String evaluate(InputSource source)
199 throws XPathExpressionException;
200 }