1 /*

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

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

     4  *

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

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

     7  * published by the Free Software Foundation.  Oracle designates this

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

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

    10  *

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

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

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

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

    15  * accompanied this code).

    16  *

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

    18  * 2 along with this work; if not, write to the Free Software Foundation,

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

    20  *

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

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package javax.xml.bind;

    27 

    28 import javax.xml.namespace.QName;

    29 import java.io.Serializable;

    30 

    31 /**

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

    33  *

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

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

    36  * with the following properties

    37  * <ul>

    38  *   <li>element's xml tag <b>{@code name}</b></li>

    39  *   <li><b>{@code value}</b> represents the element instance's atttribute(s) and content model</li>

    40  *   <li>element declaration's <b>{@code declaredType}</b> ({@code xs:element @type} attribute)</li>

    41  *   <li><b>{@code scope}</b> of element declaration</li>

    42  *   <li>boolean <b>{@code nil}</b> property. (element instance's <b>{@code xsi:nil}</b> attribute)</li>

    43  * </ul>

    44  *

    45  * <p>The {@code declaredType} and {@code scope} property are the

    46  * JAXB class binding for the xml type definition.

    47  * </p>

    48  *

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

    50  * complex type definition containing the schema element declaration.

    51  * </p>

    52  *

    53  * <p>There is a property constraint that if <b>{@code value}</b> is {@code null},

    54  * then {@code nil} must be {@code true}. The converse is not true to enable

    55  * representing a nil element with attribute(s). If {@code nil} is true, it is possible

    56  * that {@code value} is non-null so it can hold the value of the attributes

    57  * associated with a nil element.

    58  * </p>

    59  *

    60  * @author Kohsuke Kawaguchi, Joe Fialli

    61  * @since 1.6, JAXB 2.0

    62  */

    63 

    64 public class JAXBElement<T> implements Serializable {

    65 

    66     /** xml element tag name */

    67     final protected QName name;

    68 

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

    70     final protected Class<T> declaredType;

    71 

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

    73      *  Can be one of the following values:

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

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

    76      *     representation of complex type defintion containing

    77      *     xml element declaration.

    78      */

    79     final protected Class scope;

    80 

    81     /** xml element value.

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

    83     protected T value;

    84 

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

    86     protected boolean nil = false;

    87 

    88     /**

    89      * Designates global scope for an xml element.

    90      */

    91     public static final class GlobalScope {}

    92 

    93     /**

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

    95      *

    96      * @param name          Java binding of xml element tag name

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

    98      * @param scope

    99      *      Java binding of scope of xml element declaration.

   100      *      Passing null is the same as passing {@code GlobalScope.class}

   101      * @param value

   102      *      Java instance representing xml element's value.

   103      * @see #getScope()

   104      * @see #isTypeSubstituted()

   105      */

   106     public JAXBElement(QName name,

   107                        Class<T> declaredType,

   108                        Class scope,

   109                        T value) {

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

   111             throw new IllegalArgumentException();

   112         this.declaredType = declaredType;

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

   114         this.scope = scope;

   115         this.name = name;

   116         setValue(value);

   117     }

   118 

   119     /**

   120      * Construct an xml element instance.

   121      *

   122      * This is just a convenience method for {@code new JAXBElement(name,declaredType,GlobalScope.class,value)}

   123      */

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

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

   126     }

   127 

   128     /**

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

   130      */

   131     public Class<T> getDeclaredType() {

   132         return declaredType;

   133     }

   134 

   135     /**

   136      * Returns the xml element tag name.

   137      */

   138     public QName getName() {

   139         return name;

   140     }

   141 

   142     /**

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

   144      *

   145      * <p>When this property is set to {@code null}, {@code isNil()} must by {@code true}.

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

   147      *

   148      * @see #isTypeSubstituted()

   149      */

   150     public void setValue(T t) {

   151         this.value = t;

   152     }

   153 

   154     /**

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

   156      *

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

   158      * this value is {@code null}</p>

   159      */

   160     public T getValue() {

   161         return value;

   162     }

   163 

   164     /**

   165      * Returns scope of xml element declaration.

   166      *

   167      * @see #isGlobalScope()

   168      * @return {@code GlobalScope.class} if this element is of global scope.

   169      */

   170     public Class getScope() {

   171         return scope;

   172     }

   173 

   174     /**

   175      * <p>Returns {@code true} iff this element instance content model

   176      * is nil.</p>

   177      *

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

   179      * Note that the converse is not true, when this property is {@code true},

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

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

   182      */

   183     public boolean isNil() {

   184         return (value == null) || nil;

   185     }

   186 

   187     /**

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

   189      *

   190      * @see #isNil()

   191      */

   192     public void setNil(boolean value) {

   193         this.nil = value;

   194     }

   195 

   196     /* Convenience methods

   197      * (Not necessary but they do unambiguously conceptualize

   198      *  the rationale behind this class' fields.)

   199      */

   200 

   201     /**

   202      * Returns true iff this xml element declaration is global.

   203      */

   204     public boolean isGlobalScope() {

   205         return this.scope == GlobalScope.class;

   206     }

   207 

   208     /**

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

   210      * type than xml element declaration's declared type.

   211      */

   212     public boolean isTypeSubstituted() {

   213         if(value==null)     return false;

   214         return value.getClass() != declaredType;

   215     }

   216 

   217     private static final long serialVersionUID = 1L;

   218 }