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    <p>JAXBElement is used to preserve the element name/namespace in use cases where enough information is not present in the object model. The most common occurence is with substitution groups:</p> <p><strong>With Substitution Group:</strong></p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org" xmlns="http://www.example.org" elementFormDefault="qualified"&gt; &lt;xs:element name="root"&gt; &lt;xs:complexType&gt; &lt;xs:sequence&gt; &lt;xs:element ref="anElement"/&gt; &lt;/xs:sequence&gt; &lt;/xs:complexType&gt; &lt;/xs:element&gt; &lt;xs:element name="anElement" type="xs:string"/&gt; &lt;xs:element name="aSubstituteElement" type="xs:string" substitutionGroup="anElement"/&gt; &lt;/xs:schema&gt; </code></pre> <p>Will generate:</p> <pre><code>package org.example; import javax.xml.bind.JAXBElement; import javax.xml.bind.annotation.*; @XmlAccessorType(XmlAccessType.FIELD) @XmlType(name = "", propOrder = { "anElement" }) @XmlRootElement(name = "root") public class Root { @XmlElementRef(name = "anElement", namespace = "http://www.example.org", type = JAXBElement.class) protected JAXBElement&lt;String&gt; anElement; public JAXBElement&lt;String&gt; getAnElement() { return anElement; } public void setAnElement(JAXBElement&lt;String&gt; value) { this.anElement = ((JAXBElement&lt;String&gt; ) value); } } </code></pre> <p><strong>Without Substitution Group:</strong></p> <p>If you remove the substitution group:</p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org" xmlns="http://www.example.org" elementFormDefault="qualified"&gt; &lt;xs:element name="root"&gt; &lt;xs:complexType&gt; &lt;xs:sequence&gt; &lt;xs:element ref="anElement"/&gt; &lt;/xs:sequence&gt; &lt;/xs:complexType&gt; &lt;/xs:element&gt; &lt;xs:element name="anElement" type="xs:string"/&gt; &lt;/xs:schema&gt; </code></pre> <p>The following class will be generated:</p> <pre><code>package org.example; import javax.xml.bind.annotation.*; @XmlAccessorType(XmlAccessType.FIELD) @XmlType(name = "", propOrder = { "anElement" }) @XmlRootElement(name = "root") public class Root { @XmlElement(required = true) protected String anElement; public String getAnElement() { return anElement; } public void setAnElement(String value) { this.anElement = value; } } </code></pre> <p>You may also get a JAXBElement when you unmarshal, compare the following examples:</p> <ul> <li><a href="http://wiki.eclipse.org/EclipseLink/Examples/MOXy/GettingStarted/TheBasics" rel="noreferrer">Without any JAXB metada the result will be wrapped in a JAXBElement</a></li> <li><a href="http://wiki.eclipse.org/EclipseLink/Examples/MOXy/GettingStarted/JAXBCustomizations" rel="noreferrer">Using @XmlRootElement eliminates the root level JAXBElement</a></li> </ul>
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    1. POWhy does JAXB sometimes map to JAXBElement?
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    1. USBlaise Doughan
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    1. COThanks, substitution groups are indeed where this is happening. So is it then a bug that in `afterUnmarshal(Unmarshaller u, Object parent)` these substitutable classes are being passed their own JAXBElement as their `parent`? Especially since there doesn't seem to be a way to get the real parent element from the JAXBElement.
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    2. COThis appears to be a bug in Metro JAXB (the reference implementation, included in Java SE 6). In the MOXy JAXB implementation (http://www.eclipse.org/eclipselink/moxy.php) the correct parent object is passed to the afterUnmarshal method.
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