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 * Copyright (c) 2004, 2013, Oracle and/or its affiliates. All rights reserved.

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

 *

 * 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 1.6, 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;

}