1 /*
2 * Copyright (c) 2015 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 package javax.xml.xpath;
26
27 import java.util.Objects;
28 import javax.xml.namespace.QName;
29 import org.w3c.dom.Node;
30 /**
31 * The {@code XPathEvaluationResult} interface represents the result of the
32 * evaluation of an XPath expression within the context of a particular node.
33 * The evaluation of an XPath expression can result in various result types as
34 * defined in XML Path Language (XPath) Version 1.0.
35 * <p>
36 *
37 * @param <T> the object type returned by the XPath evaluation.
38 * @see <a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version
39 * 1.0</a>
40 *
41 * @since 1.9
42 */
43 public interface XPathEvaluationResult<T> {
44
45 /**
46 * XPathResultType represents possible return types of an XPath evaluation.
47 * Provided as an enum type, it allows the use of switch statement. At the
48 * same time, a mapping is provided between the original QName types in
49 * {@link XPathConstants} and class types used in the generic methods.
50 */
51 public static enum XPathResultType {
52 /**
53 * Any type that represents any of the 5 other types listed below.
54 * Maps to {@link XPathEvaluationResult}.
55 */
56 ANY(new QName("http://www.w3.org/1999/XSL/Transform", "any"), XPathEvaluationResult.class),
57 /**
58 * The XPath 1.0 boolean data type. Maps to Java {@link Boolean}.
59 */
60 BOOLEAN(XPathConstants.BOOLEAN, Boolean.class),
61 /**
62 * The XPath 1.0 Number data type. Maps to Java {@link Number}. Of the
63 * subtypes of Number, only Double, Integer and Long are required.
64 */
65 NUMBER(XPathConstants.NUMBER, Number.class),
66 /**
67 * The XPath 1.0 String data type. Maps to Java {@link String}.
68 */
69 STRING(XPathConstants.STRING, String.class),
70 /**
71 * The XPath 1.0 NodeSet data type. Maps to {@link org.w3c.dom.NodeList}.
72 */
73 NODESET(XPathConstants.NODESET, XPathNodes.class),
74 /**
75 * The XPath 1.0 NodeSet data type. Maps to {@link org.w3c.dom.Node}.
76 */
77 NODE(XPathConstants.NODE, Node.class);
78
79 final QName qnameType;
80 final Class<?> clsType;
81 XPathResultType(QName qnameType, Class<?> clsType) {
82 this.qnameType = qnameType;
83 this.clsType = clsType;
84 }
85
86 /**
87 * Compares this type to the specified class type.
88 * @param clsType class type
89 * @return true if the argument is not null and is a class type that
90 * matches that this type represents, false otherwise.
91 */
92 private boolean equalsClassType(Class<?> clsType) {
93 Objects.nonNull(clsType);
94 if (clsType.isAssignableFrom(this.clsType)) {
95 return true;
96 }
97 return false;
98 }
99
100 /**
101 * Returns the QName type as specified in {@link XPathConstants} that
102 * corresponds to the specified class type.
103 * @param clsType a class type that the enum type supports
104 * @return the QName type that matches with the specified class type,
105 * null if there is no match
106 */
107 static public QName getQNameType(Class<?> clsType) {
108 for (XPathResultType type : XPathResultType.values()) {
109 if (type.equalsClassType(clsType)) {
110 return type.qnameType;
111 }
112 }
113 return null;
114 }
115 }
116
117 /**
118 * Return the result type as an enum specified by {@code XPathResultType}
119 * @return the result type
120 */
121 public XPathResultType type();
122
123 /**
124 * Returns the value of the result as the type <T> specified for the class.
125 *
126 * @return The value of the result.
127 */
128 public T value();
129
130 }