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 package com.sun.xml.internal.bind.marshaller;

 import java.io.OutputStream;

 import javax.xml.bind.JAXBContext;

 import javax.xml.stream.XMLEventWriter;

 import javax.xml.stream.XMLStreamWriter;

 import javax.xml.transform.dom.DOMResult;

 import org.w3c.dom.Node;

 // be careful about changing this class. this class is supposed to be

 // extended by users and therefore we are not allowed to break

 // those user code.

 //

 // this means:

 // - don't add any abstract method

 // - don't change any existing method signature

 // - don't remove any existing method.

 /**

  * Implemented by the user application to determine URI -> prefix

  * mapping.

  *

  * This is considered as an interface, though it's implemented

  * as an abstract class to make it easy to add new methods in

  * a future.

  *

  * @author

  *     Kohsuke Kawaguchi (kohsuke.kawaguchi@sun.com)

  */

 public abstract class NamespacePrefixMapper {

     private static final String[] EMPTY_STRING = new String[0];

     /**

      * Returns a preferred prefix for the given namespace URI.

      *

      * This method is intended to be overrided by a derived class.

      *

      * <p>

      * As noted in the return value portion of the javadoc, there

      * are several cases where the preference cannot be honored.

      * Specifically, as of JAXB RI 2.0 and onward:

      *

      * <ol>

      * <li>

      * If the prefix returned is already in use as one of the in-scope

      * namespace bindings. This is partly necessary for correctness

      * (so that we don't unexpectedly change the meaning of QNames

      * bound to {@link String}), partly to simplify the marshaller.

      * <li>

      * If the prefix returned is "" yet the current {@link JAXBContext}

      * includes classes that use the empty namespace URI. This allows

      * the JAXB RI to reserve the "" prefix for the empty namespace URI,

      * which is the only possible prefix for the URI.

      * This restriction is also to simplify the marshaller.

      * </ol>

      *

      * @param namespaceUri

      *      The namespace URI for which the prefix needs to be found.

      *      Never be null. "" is used to denote the default namespace.

      * @param suggestion

      *      When the content tree has a suggestion for the prefix

      *      to the given namespaceUri, that suggestion is passed as a

      *      parameter. Typicall this value comes from the QName.getPrefix

      *      to show the preference of the content tree. This parameter

      *      may be null, and this parameter may represent an already

      *      occupied prefix.

      * @param requirePrefix

      *      If this method is expected to return non-empty prefix.

      *      When this flag is true, it means that the given namespace URI

      *      cannot be set as the default namespace.

      *

      * @return

      *      null if there's no prefered prefix for the namespace URI.

      *      In this case, the system will generate a prefix for you.

      *

      *      Otherwise the system will try to use the returned prefix,

      *      but generally there's no guarantee if the prefix will be

      *      actually used or not.

      *

      *      return "" to map this namespace URI to the default namespace.

      *      Again, there's no guarantee that this preference will be

      *      honored.

      *

      *      If this method returns "" when requirePrefix=true, the return

      *      value will be ignored and the system will generate one.

      *

      * @since JAXB 1.0.1

      */

     public abstract String getPreferredPrefix(String namespaceUri, String suggestion, boolean requirePrefix);

     /**

      * Returns a list of namespace URIs that should be declared

      * at the root element.

      *

      * <p>

      * By default, the JAXB RI 1.0.x produces namespace declarations only when

      * they are necessary, only at where they are used. Because of this

      * lack of look-ahead, sometimes the marshaller produces a lot of

      * namespace declarations that look redundant to human eyes. For example,

      * <pre><xmp>

      * <?xml version="1.0"?>

      * <root>

      *   <ns1:child xmlns:ns1="urn:foo"> ... </ns1:child>

      *   <ns2:child xmlns:ns2="urn:foo"> ... </ns2:child>

      *   <ns3:child xmlns:ns3="urn:foo"> ... </ns3:child>

      *   ...

      * </root>

      * </xmp></pre>

      *

      * <p>

      * The JAXB RI 2.x mostly doesn't exhibit this behavior any more,

      * as it declares all statically known namespace URIs (those URIs

      * that are used as element/attribute names in JAXB annotations),

      * but it may still declare additional namespaces in the middle of

      * a document, for example when (i) a QName as an attribute/element value

      * requires a new namespace URI, or (ii) DOM nodes as a portion of an object

      * tree requires a new namespace URI.

      *

      * <p>

      * If you know in advance that you are going to use a certain set of

      * namespace URIs, you can override this method and have the marshaller

      * declare those namespace URIs at the root element.

      *

      * <p>

      * For example, by returning <code>new String[]{"urn:foo"}</code>,

      * the marshaller will produce:

      * <pre><xmp>

      * <?xml version="1.0"?>

      * <root xmlns:ns1="urn:foo">

      *   <ns1:child> ... </ns1:child>

      *   <ns1:child> ... </ns1:child>

      *   <ns1:child> ... </ns1:child>

      *   ...

      * </root>

      * </xmp></pre>

      * <p>

      * To control prefixes assigned to those namespace URIs, use the

      * {@link #getPreferredPrefix(String, String, boolean)} method.

      *

      * @return

      *      A list of namespace URIs as an array of {@link String}s.

      *      This method can return a length-zero array but not null.

      *      None of the array component can be null. To represent

      *      the empty namespace, use the empty string <code>""</code>.

      *

      * @since

      *      JAXB RI 1.0.2

      */

     public String[] getPreDeclaredNamespaceUris() {

         return EMPTY_STRING;

     }

     /**

      * Similar to {@link #getPreDeclaredNamespaceUris()} but allows the

      * (prefix,nsUri) pairs to be returned.

      *

      * <p>

      * With {@link #getPreDeclaredNamespaceUris()}, applications who wish to control

      * the prefixes as well as the namespaces needed to implement both

      * {@link #getPreDeclaredNamespaceUris()} and {@link #getPreferredPrefix(String, String, boolean)}.

      *

      * <p>

      * This version eliminates the needs by returning an array of pairs.

      *

      * @return

      *      always return a non-null (but possibly empty) array. The array stores

      *      data like (prefix1,nsUri1,prefix2,nsUri2,...) Use an empty string to represent

      *      the empty namespace URI and the default prefix. Null is not allowed as a value

      *      in the array.

      *

      * @since

      *      JAXB RI 2.0 beta

      */

     public String[] getPreDeclaredNamespaceUris2() {

         return EMPTY_STRING;

     }

     /**

      * Returns a list of (prefix,namespace URI) pairs that represents

      * namespace bindings available on ancestor elements (that need not be repeated

      * by the JAXB RI.)

      *

      * <p>

      * Sometimes JAXB is used to marshal an XML document, which will be

      * used as a subtree of a bigger document. When this happens, it's nice

      * for a JAXB marshaller to be able to use in-scope namespace bindings

      * of the larger document and avoid declaring redundant namespace URIs.

      *

      * <p>

      * This is automatically done when you are marshalling to {@link XMLStreamWriter},

      * {@link XMLEventWriter}, {@link DOMResult}, or {@link Node}, because

      * those output format allows us to inspect what's currently available

      * as in-scope namespace binding. However, with other output format,

      * such as {@link OutputStream}, the JAXB RI cannot do this automatically.

      * That's when this method comes into play.

      *

      * <p>

      * Namespace bindings returned by this method will be used by the JAXB RI,

      * but will not be re-declared. They are assumed to be available when you insert

      * this subtree into a bigger document.

      *

      * <p>

      * It is <b>NOT</b> OK to return  the same binding, or give

      * the receiver a conflicting binding information.

      * It's a responsibility of the caller to make sure that this doesn't happen

      * even if the ancestor elements look like:

      * <pre><xmp>

      *   <foo:abc xmlns:foo="abc">

      *     <foo:abc xmlns:foo="def">

      *       <foo:abc xmlns:foo="abc">

      *         ... JAXB marshalling into here.

      *       </foo:abc>

      *     </foo:abc>

      *   </foo:abc>

      * </xmp></pre>

      *

      * @return

      *      always return a non-null (but possibly empty) array. The array stores

      *      data like (prefix1,nsUri1,prefix2,nsUri2,...) Use an empty string to represent

      *      the empty namespace URI and the default prefix. Null is not allowed as a value

      *      in the array.

      *

      * @since JAXB RI 2.0 beta

      */

     public String[] getContextualNamespaceDecls() {

         return EMPTY_STRING;

     }

 }