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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 package javax.xml.bind;

 import javax.xml.namespace.QName;

 import java.io.Serializable;

 /**

  * <p>JAXB representation of an Xml Element.</p>

  *

  * <p>This class represents information about an Xml Element from both the element

  * declaration within a schema and the element instance value within an xml document

  * with the following properties

  * <ul>

  *   <li>element's xml tag <b><tt>name</tt></b></li>

  *   <li><b><tt>value</tt></b> represents the element instance's atttribute(s) and content model</li>

  *   <li>element declaration's <b><tt>declaredType</tt></b> (<tt>xs:element @type</tt> attribute)</li>

  *   <li><b><tt>scope</tt></b> of element declaration</li>

  *   <li>boolean <b><tt>nil</tt></b> property. (element instance's <tt><b>xsi:nil</b></tt> attribute)</li>

  * </ul>

  *

  * <p>The <tt>declaredType</tt> and <tt>scope</tt> property are the

  * JAXB class binding for the xml type definition.

  * </p>

  *

  * <p><b><tt>Scope</tt></b> is either {@link GlobalScope} or the Java class representing the

  * complex type definition containing the schema element declaration.

  * </p>

  *

  * <p>There is a property constraint that if <b><tt>value</tt></b> is <tt>null</tt>,

  * then <tt>nil</tt> must be <tt>true</tt>. The converse is not true to enable

  * representing a nil element with attribute(s). If <tt>nil</tt> is true, it is possible

  * that <tt>value</tt> is non-null so it can hold the value of the attributes

  * associated with a nil element.

  * </p>

  *

  * @author Kohsuke Kawaguchi, Joe Fialli

  * @since JAXB 2.0

  */

 public class JAXBElement<T> implements Serializable {

     /** xml element tag name */

     final protected QName name;

     /** Java datatype binding for xml element declaration's type. */

     final protected Class<T> declaredType;

     /** Scope of xml element declaration representing this xml element instance.

      *  Can be one of the following values:

      *  - {@link GlobalScope} for global xml element declaration.

      *  - local element declaration has a scope set to the Java class

      *     representation of complex type defintion containing

      *     xml element declaration.

      */

     final protected Class scope;

     /** xml element value.

         Represents content model and attributes of an xml element instance. */

     protected T value;

     /** true iff the xml element instance has xsi:nil="true". */

     protected boolean nil = false;

     /**

      * Designates global scope for an xml element.

      */

     public static final class GlobalScope {}

     /**

      * <p>Construct an xml element instance.</p>

      *

      * @param name          Java binding of xml element tag name

      * @param declaredType  Java binding of xml element declaration's type

      * @param scope

      *      Java binding of scope of xml element declaration.

      *      Passing null is the same as passing <tt>GlobalScope.class</tt>

      * @param value

      *      Java instance representing xml element's value.

      * @see #getScope()

      * @see #isTypeSubstituted()

      */

     public JAXBElement(QName name,

                        Class<T> declaredType,

                        Class scope,

                        T value) {

         if(declaredType==null || name==null)

             throw new IllegalArgumentException();

         this.declaredType = declaredType;

         if(scope==null)     scope = GlobalScope.class;

         this.scope = scope;

         this.name = name;

         setValue(value);

     }

     /**

      * Construct an xml element instance.

      *

      * This is just a convenience method for <tt>new JAXBElement(name,declaredType,GlobalScope.class,value)</tt>

      */

     public JAXBElement(QName name, Class<T> declaredType, T value ) {

         this(name,declaredType,GlobalScope.class,value);

     }

     /**

      * Returns the Java binding of the xml element declaration's type attribute.

      */

     public Class<T> getDeclaredType() {

         return declaredType;

     }

     /**

      * Returns the xml element tag name.

      */

     public QName getName() {

         return name;

     }

     /**

      * <p>Set the content model and attributes of this xml element.</p>

      *

      * <p>When this property is set to <tt>null</tt>, <tt>isNil()</tt> must by <tt>true</tt>.

      *    Details of constraint are described at {@link #isNil()}.</p>

      *

      * @see #isTypeSubstituted()

      */

     public void setValue(T t) {

         this.value = t;

     }

     /**

      * <p>Return the content model and attribute values for this element.</p>

      *

      * <p>See {@link #isNil()} for a description of a property constraint when

      * this value is <tt>null</tt></p>

      */

     public T getValue() {

         return value;

     }

     /**

      * Returns scope of xml element declaration.

      *

      * @see #isGlobalScope()

      * @return <tt>GlobalScope.class</tt> if this element is of global scope.

      */

     public Class getScope() {

         return scope;

     }

     /**

      * <p>Returns <tt>true</tt> iff this element instance content model

      * is nil.</p>

      *

      * <p>This property always returns <tt>true</tt> when {@link #getValue()} is null.

      * Note that the converse is not true, when this property is <tt>true</tt>,

      * {@link #getValue()} can contain a non-null value for attribute(s). It is

      * valid for a nil xml element to have attribute(s).</p>

      */

     public boolean isNil() {

         return (value == null) || nil;

     }

     /**

      * <p>Set whether this element has nil content.</p>

      *

      * @see #isNil()

      */

     public void setNil(boolean value) {

         this.nil = value;

     }

     /* Convenience methods

      * (Not necessary but they do unambiguously conceptualize

      *  the rationale behind this class' fields.)

      */

     /**

      * Returns true iff this xml element declaration is global.

      */

     public boolean isGlobalScope() {

         return this.scope == GlobalScope.class;

     }

     /**

      * Returns true iff this xml element instance's value has a different

      * type than xml element declaration's declared type.

      */

     public boolean isTypeSubstituted() {

         if(value==null)     return false;

         return value.getClass() != declaredType;

     }

     private static final long serialVersionUID = 1L;

 }