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package javax.xml.namespace;

import java.util.Iterator;

/**

 * Interface for read only XML Namespace context processing.

 *

 * <p>An XML Namespace has the properties:

 * <ul>

 *   <li>Namespace URI:

 *       Namespace name expressed as a URI to which the prefix is bound</li>

 *   <li>prefix: syntactically, this is the part of the attribute name

 *       following the {@code XMLConstants.XMLNS_ATTRIBUTE}

 *       ("xmlns") in the Namespace declaration</li>

 * </ul>

 * <p>example:

 * {@code <element xmlns:prefix="http://Namespace-name-URI">}

 *

 * <p>All {@code get*(*)} methods operate in the current scope

 * for Namespace URI and prefix resolution.

 *

 * <p>Note that a Namespace URI can be bound to

 * <strong>multiple</strong> prefixes in the current scope.  This can

 * occur when multiple {@code XMLConstants.XMLNS_ATTRIBUTE}

 * ("xmlns") Namespace declarations occur in the same Start-Tag and

 * refer to the same Namespace URI. e.g.<br>

 * <pre> {@code

 * <element xmlns:prefix1="http://Namespace-name-URI"

 *          xmlns:prefix2="http://Namespace-name-URI"> }

 * </pre>

 * This can also occur when the same Namespace URI is used in multiple

 * {@code XMLConstants.XMLNS_ATTRIBUTE} ("xmlns") Namespace

 * declarations in the logical parent element hierarchy.  e.g.<br>

 * <pre> {@code

 * <parent xmlns:prefix1="http://Namespace-name-URI">

 *   <child xmlns:prefix2="http://Namespace-name-URI">

 *     ...

 *   </child>

 * </parent> }

 * </pre>

 *

 * <p>A prefix can only be bound to a <strong>single</strong>

 * Namespace URI in the current scope.

 *

 * @author Jeff Suttor

 * @see javax.xml.XMLConstants

 *   javax.xml.XMLConstants for declarations of common XML values

 * @see <a href="http://www.w3.org/TR/xmlschema-2/#QName">

 *   XML Schema Part2: Datatypes</a>

 *   Namespaces in XML</a>

 * @since 1.5

 */

public interface NamespaceContext {

    /**

     * Get Namespace URI bound to a prefix in the current scope.

     *

     * <p>When requesting a Namespace URI by prefix, the following

     * table describes the returned Namespace URI value for all

     * possible prefix values:

     *

     * <table class="striped">

     *   <caption>Return value for specified prefixes</caption>

     *   <thead>

     *     <tr>

     *       <th scope="col">prefix parameter</th>

     *       <th scope="col">Namespace URI return value</th>

     *     </tr>

     *   </thead>

     *   <tbody>

     *     <tr>

     *       <th scope="row">{@code DEFAULT_NS_PREFIX} ("")</th>

     *       <td>default Namespace URI in the current scope or

     *         <code> {@link

     *         javax.xml.XMLConstants#NULL_NS_URI XMLConstants.NULL_NS_URI("")}

     *         </code>

     *         when there is no default Namespace URI in the current scope</td>

     *     </tr>

     *     <tr>

     *       <th scope="row">bound prefix</th>

     *       <td>Namespace URI bound to prefix in current scope</td>

     *     </tr>

     *     <tr>

     *       <th scope="row">unbound prefix</th>

     *       <td>

     *         <code> {@link

     *         javax.xml.XMLConstants#NULL_NS_URI XMLConstants.NULL_NS_URI("")}

     *         </code>

     *       </td>

     *     </tr>

     *     <tr>

     *       <th scope="row">{@code XMLConstants.XML_NS_PREFIX} ("xml")</th>

     *       <td>{@code XMLConstants.XML_NS_URI}

     *           ("http://www.w3.org/XML/1998/namespace")</td>

     *     </tr>

     *     <tr>

     *       <th scope="row">{@code XMLConstants.XMLNS_ATTRIBUTE} ("xmlns")</th>

     *       <td>{@code XMLConstants.XMLNS_ATTRIBUTE_NS_URI}

     *         ("http://www.w3.org/2000/xmlns/")</td>

     *     </tr>

     *     <tr>

     *       <th scope="row">{@code null}</th>

     *       <td>{@code IllegalArgumentException} is thrown</td>

     *     </tr>

     *    </tbody>

     * </table>

     *

     * @param prefix prefix to look up

     *

     * @return Namespace URI bound to prefix in the current scope

     *

     * @throws IllegalArgumentException When {@code prefix} is

     *   {@code null}

     */

    String getNamespaceURI(String prefix);

    /**

     * Get prefix bound to Namespace URI in the current scope.

     *

     * <p>To get all prefixes bound to a Namespace URI in the current

     * scope, use {@link #getPrefixes(String namespaceURI)}.

     *

     * <p>When requesting a prefix by Namespace URI, the following

     * table describes the returned prefix value for all Namespace URI

     * values:

     *

     * <table class="striped">

     * <caption>Return value for specified Namespace URIs</caption>

     *   <thead>

     *     <tr>

     *       <th scope="col">Namespace URI parameter</th>

     *       <th scope="col">prefix value returned</th>

     *     </tr>

     *   </thead>

     *   <tbody>

     *     <tr>

     *       <th scope="row">{@code <default Namespace URI>}</th>

     *       <td>{@code XMLConstants.DEFAULT_NS_PREFIX} ("")

     *       </td>

     *     </tr>

     *     <tr>

     *       <th scope="row">bound Namespace URI</th>

     *       <td>prefix bound to Namespace URI in the current scope,

     *           if multiple prefixes are bound to the Namespace URI in

     *           the current scope, a single arbitrary prefix, whose

     *           choice is implementation dependent, is returned</td>

     *     </tr>

     *     <tr>

     *       <th scope="row">unbound Namespace URI</th>

     *       <td>{@code null}</td>

     *     </tr>

     *     <tr>

     *       <th scope="row">{@code XMLConstants.XML_NS_URI}

     *           ("http://www.w3.org/XML/1998/namespace")</th>

     *       <td>{@code XMLConstants.XML_NS_PREFIX} ("xml")</td>

     *     </tr>

     *     <tr>

     *       <th scope="row">{@code XMLConstants.XMLNS_ATTRIBUTE_NS_URI}

     *           ("http://www.w3.org/2000/xmlns/")</th>

     *       <td>{@code XMLConstants.XMLNS_ATTRIBUTE} ("xmlns")</td>

     *     </tr>

     *     <tr>

     *       <th scope="row">{@code null}</th>

     *       <td>{@code IllegalArgumentException} is thrown</td>

     *     </tr>

     *   </tbody>

     * </table>

     *

     * @param namespaceURI URI of Namespace to lookup

     *

     * @return prefix bound to Namespace URI in current context

     *

     * @throws IllegalArgumentException When {@code namespaceURI} is

     *   {@code null}

     */

    String getPrefix(String namespaceURI);

    /**

     * Get all prefixes bound to a Namespace URI in the current

     * scope.

     *

     * <p>An Iterator over String elements is returned in an arbitrary,

     * <strong>implementation dependent</strong>, order.

     *

     * <p><strong>The {@code Iterator} is

     * <em>not</em> modifiable.  e.g. the

     * {@code remove()} method will throw

     * {@code UnsupportedOperationException}.</strong>

     *

     * <p>When requesting prefixes by Namespace URI, the following

     * table describes the returned prefixes value for all Namespace

     * URI values:

     *

     * <table class="striped">

     *   <caption>Return value for specified Namespace URIs</caption>

     *   <thead>

     *     <tr>

     *       <th scope="col">Namespace URI parameter</th>

     *       <th scope="col">prefixes value returned</th>

     *     </tr>

     *   </thead>

     *   <tbody>

     *     <tr>

     *       <th scope="row">bound Namespace URI,

     *         including the {@code <default Namespace URI>}</th>

     *       <td>

     *         {@code Iterator} over prefixes bound to Namespace URI in

     *         the current scope in an arbitrary,

     *         <strong>implementation dependent</strong>,

     *         order

     *       </td>

     *     </tr>

     *     <tr>

     *       <th scope="row">unbound Namespace URI</th>

     *       <td>empty {@code Iterator}</td>

     *     </tr>

     *     <tr>

     *       <th scope="row">{@code XMLConstants.XML_NS_URI}

     *           ("http://www.w3.org/XML/1998/namespace")</th>

     *       <td>{@code Iterator} with one element set to

     *         {@code XMLConstants.XML_NS_PREFIX} ("xml")</td>

     *     </tr>

     *     <tr>

     *       <th scope="row">{@code XMLConstants.XMLNS_ATTRIBUTE_NS_URI}

     *           ("http://www.w3.org/2000/xmlns/")</th>

     *       <td>{@code Iterator} with one element set to

     *         {@code XMLConstants.XMLNS_ATTRIBUTE} ("xmlns")</td>

     *     </tr>

     *     <tr>

     *       <th scope="row">{@code null}</th>

     *       <td>{@code IllegalArgumentException} is thrown</td>

     *     </tr>

     *   </tbody>

     * </table>

     *

     * @param namespaceURI URI of Namespace to lookup

     *

     * @return {@code Iterator} for all prefixes bound to the

     *   Namespace URI in the current scope

     *

     * @throws IllegalArgumentException When {@code namespaceURI} is

     *   {@code null}

     */

    Iterator<String> getPrefixes(String namespaceURI);

}