XPathEvaluationResult.java revision 692:b13f7d2000cf 
1/*
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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).
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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25package javax.xml.xpath;
26
27import java.util.Objects;
28import javax.xml.namespace.QName;
29import 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 */
43public 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 &lt;T&gt; specified for the class.
125     *
126     * @return The value of the result.
127     */
128    public T value();
129
130}
131