/**
 * 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;
    }
}

marshaller.setProperty("com.sun.xml.bind.xmlDeclaration", true);

marshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);

marshaller.setProperty("com.sun.xml.bind.XmlAccessorFactory", true);

<bindings xmlns:tns="http://example.com/myns"
          xmlns="http://java.sun.com/xml/ns/jaxb" version="2.1">
    <bindings
            ...
            scd="tns:foo">
        <!-- this customization applies to the global element declaration -->
        <!-- 'foo' in the http://example.com/myns namespace -->
        <class name="FooElement"/>
    </bindings>
    <bindings
            ...
            scd="~tns:bar">
        <!-- this customization applies to the global type declaration -->
        <!-- 'bar' in the http://example.com/myns namespace -->
        <class name="BarType"/>
    </bindings>
</bindings>  

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
           xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
           jaxb:extensionBindingPrefixes="xjc"
           jaxb:version="2.0">

    <xs:annotation>
        <xs:appinfo>
            <jaxb:globalBindings>
                <xjc:superClass
                        name="org.acme.RocketBooster"/>
            </jaxb:globalBindings>
        </xs:appinfo>
    </xs:annotation>
    
    ...
    
</xs:schema>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
           xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
           jaxb:extensionBindingPrefixes="xjc"
           jaxb:version="2.0">

    <xs:annotation>
        <xs:appinfo>
            <jaxb:globalBindings>
                <xjc:superInterface
                        name="org.acme.RocketBooster"/>
            </jaxb:globalBindings>
        </xs:appinfo>
    </xs:annotation>

    ...

</xs:schema>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
           xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
           jaxb:extensionBindingPrefixes="xjc"
           jaxb:version="2.0">
    
    ...
    
    <xsd:simpleType name="LayerRate_T">
        <xsd:annotation>
            <xsd:appinfo>
                <xjc:javaType name="org.acme.foo.LayerRate"
                              adapter="org.acme.foo.LayerRateAdapter"/>
            </xsd:appinfo>
        </xsd:annotation>
        
        ... gory simple type definition here ...
        
    </xsd:simpleType>
</xsd:schema>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
           xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
           jaxb:extensionBindingPrefixes="xjc"
           jaxb:version="2.0">
    
    <xsd:annotation>
        <xsd:appinfo>
            <jaxb:globalBindings>
                <xjc:javaType name="org.acme.foo.MyDateType"
                              xmlType="xsd:dateTime"
                              adapter="org.acme.foo.MyAdapterImpl"/>
            </jaxb:globalBindings>
        </xsd:appinfo>
    </xsd:annotation>

    ...
    
</xsd:schema>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
           xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
           jaxb:extensionBindingPrefixes="xjc"
           jaxb:version="2.0">

    <xs:annotation>
        <xs:appinfo>
            <jaxb:globalBindings generateValueClass="false">
                <xjc:simple/>
            </jaxb:globalBindings>
        </xs:appinfo>
    </xs:annotation>

    ...

</xs:schema>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
           jaxb:extensionBindingPrefixes="xjc"
           xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
           jaxb:version="2.0"
           elementFormDefault="qualified">

    <xs:annotation>
        <xs:appinfo>
            <jaxb:globalBindings>
                <xjc:treatRestrictionLikeNewType/>
            </jaxb:globalBindings>
        </xs:appinfo>
    </xs:annotation>

    <xs:complexType name="DerivedType">
        <xs:complexContent>
            <xs:restriction base="ResponseOptionType">
                <xs:sequence>
                    <xs:element name="foo" type="xs:string"/>
                </xs:sequence>
            </xs:restriction>
        </xs:complexContent>
    </xs:complexType>

    <xs:complexType name="ResponseOptionType">
        <xs:sequence>
            <xs:element name="foo" type="xs:string"
                        maxOccurs="unbounded"/>
        </xs:sequence>
    </xs:complexType>

</xs:schema>

public class DerivedType {
    protected String foo;

    public String getFoo() { return foo; }
    public void setFoo(String value) { this.foo = value; }
} 

public class DerivedType extends ResponseOptionType {

    // it simply inherits List<String> ResponseOptionType.getFoo()

}

<xs:element name="Model" type="Model">
    <xs:annotation>
        <xs:appinfo>
            <xjc:substitutable/>
        </xs:appinfo>
    </xs:annotation>
</xs:element>

<taskdef name="xjc" classname="com.sun.tools.xjc.XJCTask">
    <classpath>
        <fileset dir="jaxb-ri/lib" includes="*.jar"/>
        <fileset dir="your-plugin" includes="*.jar"/>
    </classpath>
</taskdef>