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<div class="sect1"><!-- infolevel="all" infotype="General" -->
<h1 class="sect1"><font face="arial, helvetica, sans-serif" color="#330099">Mapping Using XPath Predicates</font></h1>
<p>By default, JAXB will use the Java field name as the XML element name:</p>
<div class="example"><a id="TLJAX406" name="TLJAX406"></a><a id="sthref167" name="sthref167"></a>
<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-24 Sample Java Code and XML Schema</font></em></strong></p>
<pre xml:space="preserve" class="oac_no_warn">
public class Customer {
@XmlElement
private String firstName;
@XmlElement
private String lastName;
}
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;customer&gt;
&lt;firstName&gt;Bob&lt;/firstName&gt;
&lt;lastName&gt;Roberts&lt;/lastName&gt;
&lt;/customer&gt;
</pre></div>
<!-- class="example" -->
<p>Or, the XML name can be customized using the name attribute of the <code>@XmlElement</code> annotation:</p>
<div class="example"><a id="TLJAX407" name="TLJAX407"></a><a id="sthref168" name="sthref168"></a>
<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-25 Sample Java Code and XML Schema</font></em></strong></p>
<pre xml:space="preserve" class="oac_no_warn">
public class Customer {
@XmlElement(name="f-name")
private String firstName;
@XmlElement(name="l-name")
private String lastName;
}
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;customer&gt;
&lt;f-name&gt;Bob&lt;/f-name&gt;
&lt;l-name&gt;Roberts&lt;/l-name&gt;
&lt;/customer&gt;
</pre></div>
<!-- class="example" -->
<p>However, sometimes elements need to be mapped based on their position in the document, or based on an attribute value of an element:</p>
<pre xml:space="preserve" class="oac_no_warn">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;node&gt;
&lt;name&gt;Jane&lt;/name&gt;
&lt;name&gt;Doe&lt;/name&gt;
&lt;node name="address"&gt;
&lt;node name="street"&gt;123 A Street&lt;/node&gt;
&lt;/node&gt;
&lt;node name="phone-number" type="work"&gt;555-1111&lt;/node&gt;
&lt;node name="phone-number" type="cell"&gt;555-2222&lt;/node&gt;
&lt;/node&gt;
</pre>
<p>For cases like this, EclipseLink MOXy allows you to use XPath predicates to define an expression that will specify the XML element's name.</p>
<a id="TLJAX408" name="TLJAX408"></a>
<div class="sect2"><a id="sthref169" name="sthref169"></a>
<h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Mapping with XPath Predicates</font></h2>
<p>An XPath predicate represents an expression that will be evaluated against the element specified. For example, the XPath statement:</p>
<pre xml:space="preserve" class="oac_no_warn">
node[2]
</pre>
<p>Would match the second occurrence of the node element ("DEF"):</p>
<pre xml:space="preserve" class="oac_no_warn">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;data&gt;
&lt;node&gt;ABC&lt;/node&gt;
&lt;node&gt;DEF&lt;/node&gt;
&lt;/data&gt;
</pre>
<p>Predicates can also match based on an attribute value:</p>
<pre xml:space="preserve" class="oac_no_warn">
node[@name='foo']
</pre>
<p>Would match the <strong>node</strong> element with the attribute <strong>name="foo"</strong> (that is, <strong>ABC</strong>). It would not match the node that contains <strong>DEF</strong>.</p>
<pre xml:space="preserve" class="oac_no_warn">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;data&gt;
&lt;node name="foo"&gt;ABC&lt;/node&gt;
&lt;node name="bar"&gt;DEF&lt;/node&gt;
&lt;/data&gt;
</pre>
<div align="center">
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<p class="note"><img src="../../dcommon/images/note_icon.png" width="16" height="16" alt="Note" style="vertical-align:middle;padding-right:5px;" />Note:</p>
<p>For more information on XPath Predicates, see "2.4 Predicates" of the XML Path Language (XPath) specification (<code><a href="http://www.w3.org/TR/xpath">http://www.w3.org/TR/xpath</a></code>).</p>
</td>
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<br /></div>
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</div>
<!-- class="sect2" -->
<a id="TLJAX409" name="TLJAX409"></a>
<div class="sect2"><a id="sthref170" name="sthref170"></a>
<h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Mapping Based on Position</font></h2>
<p>In the following example, our XML contains two <strong>name</strong> elements; the first occurrence of <strong>name</strong> should represent the <strong>Customer's</strong> first name, and the second <strong>name</strong> will be their last name. To map this, we will specify XPath expressions for each property that will match the appropriate XML element. Note that we also use <code>@XmlType(propOrder)</code> to ensure that our elements will always be in the proper positions.</p>
<div class="example"><a id="TLJAX410" name="TLJAX410"></a><a id="sthref171" name="sthref171"></a>
<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-26 Using the @XmlType(propOrder) Annotation</font></em></strong></p>
<pre xml:space="preserve" class="oac_no_warn">
package example;
import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.XmlPath;
@XmlRootElement
<strong>@XmlType(propOrder</strong>={"firstName", "lastName"})
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {
@XmlPath("name[1]/text()")
private String firstName;
@XmlPath("name[2]/text()")
private String lastName;
...
}
</pre></div>
<!-- class="example" -->
<p>This same configuration can be expressed in an EclipseLink XML Bindings document as follows:</p>
<div class="example"><a id="TLJAX411" name="TLJAX411"></a><a id="sthref172" name="sthref172"></a>
<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-27 Using the prop-order Attribute</font></em></strong></p>
<pre xml:space="preserve" class="oac_no_warn">
...
&lt;java-type name="Customer"&gt;
&lt;xml-root-element/&gt;
&lt;xml-type prop-order="firstName lastName"/&gt;
&lt;java-attributes&gt;
&lt;xml-element java-attribute="firstName" xml-path="name[1]/text()"/&gt;
&lt;xml-element java-attribute="lastName" xml-path="name[2]/text()"/&gt;
&lt;/java-attributes&gt;
&lt;/java-type&gt;
...
</pre></div>
<!-- class="example" -->
<p>This will give us the desired XML representation:</p>
<div class="example"><a id="TLJAX412" name="TLJAX412"></a><a id="sthref173" name="sthref173"></a>
<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-28 Resulting XML</font></em></strong></p>
<pre xml:space="preserve" class="oac_no_warn">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;customer&gt;
&lt;name&gt;Bob&lt;/name&gt;
&lt;name&gt;Smith&lt;/name&gt;
&lt;/customer&gt;
</pre></div>
<!-- class="example" --></div>
<!-- class="sect2" -->
<a id="TLJAX413" name="TLJAX413"></a>
<div class="sect2"><a id="sthref174" name="sthref174"></a>
<h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Mapping Based on an Attribute Value</font></h2>
<p>Since EclipseLink MOXy 2.3, you can also map to an XML element based on an Attribute value. In this example, all of our XML elements are named <strong>node</strong>, differentiated by the value of their <strong>name</strong> attribute:</p>
<div class="example"><a id="TLJAX414" name="TLJAX414"></a><a id="sthref175" name="sthref175"></a>
<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-29 Sample XML Schema</font></em></strong></p>
<pre xml:space="preserve" class="oac_no_warn">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;node&gt;
&lt;node name="first-name"&gt;Bob&lt;/node&gt;
&lt;node name="last-name"&gt;Smith&lt;/node&gt;
&lt;node name="address"&gt;
&lt;node name="street"&gt;123 A Street&lt;/node&gt;
&lt;/node&gt;
&lt;node name="phone-number" type="work"&gt;555-1111&lt;/node&gt;
&lt;node name="phone-number" type="cell"&gt;555-2222&lt;/node&gt;
&lt;/node&gt;
</pre></div>
<!-- class="example" -->
<p>We can use an XPath in the form of <code>element-name[@attribute-name='value']</code> to map each Java field:</p>
<div class="example"><a id="TLJAX415" name="TLJAX415"></a><a id="sthref176" name="sthref176"></a>
<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-30 Sample Mappings</font></em></strong></p>
<pre xml:space="preserve" class="oac_no_warn">
package example;
import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.XmlPath;
@XmlRootElement(name="node")
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {
@XmlPath("node[@name='first-name']/text()")
private String firstName;
@XmlPath("node[@name='last-name']/text()")
private String lastName;
@XmlPath("node[@name='address']")
private Address address;
@XmlPath("node[@name='phone-number']")
private List&lt;PhoneNumber&gt; phoneNumbers = new ArrayList&lt;PhoneNumber&gt;();
...
}
package example;
import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.XmlPath;
@XmlAccessorType(XmlAccessType.FIELD)
public class Address {
@XmlPath("node[@name='street']/text()")
private String street;
...
}
package example;
import javax.xml.bind.annotation.*;
@XmlAccessorType(XmlAccessType.FIELD)
public class PhoneNumber {
@XmlAttribute
private String type;
@XmlValue
private String number;
...
}
</pre></div>
<!-- class="example" --></div>
<!-- class="sect2" -->
<a id="TLJAX416" name="TLJAX416"></a>
<div class="sect2"><a id="sthref177" name="sthref177"></a>
<h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Creating "Self" Mappings</font></h2>
<p>EclipseLink allows you to configure your one-to-one mappings so the data from the target object will appear inside the source object's XML element. Expanding on the previous example, we could map the <strong>Address</strong> information so that it would appear directly under the <strong>customer</strong> element, and <em>not</em> wrapped in its own element. This is referred to as a "self" mapping, and is achieved by setting the target object's XPath to&nbsp;<strong>.</strong>&nbsp;(dot).</p>
<p><a href="#CHDGBEAC">Example 8-31</a> demonstrates a self mapping declared in annotations.</p>
<div class="example"><a id="CHDGBEAC" name="CHDGBEAC"></a><a id="TLJAX417" name="TLJAX417"></a>
<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-31 Self Mapping Example</font></em></strong></p>
<pre xml:space="preserve" class="oac_no_warn">
package example;
import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.XmlPath;
@XmlRootElement(name="node")
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {
@XmlPath("node[@name='first-name']/text()")
private String firstName;
@XmlPath("node[@name='last-name']/text()")
private String lastName;
@XmlPath(".")
private Address address;
@XmlPath("node[@name='phone-number']")
private List&lt;PhoneNumber&gt; phoneNumbers = new ArrayList&lt;PhoneNumber&gt;();
...
}
</pre></div>
<!-- class="example" -->
<p>Using a self mapping, EclipseLink produces the desired XML. The <strong>street</strong> data is stored in the root <strong>node</strong>.</p>
<pre xml:space="preserve" class="oac_no_warn">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;node&gt;
&lt;node name="first-name"&gt;Bob&lt;/node&gt;
&lt;node name="last-name"&gt;Smith&lt;/node&gt;
&lt;node name="street"&gt;123 A Street&lt;/node&gt;
&lt;node name="phone-number" type="work"&gt;555-1111&lt;/node&gt;
&lt;node name="phone-number" type="cell"&gt;555-2222&lt;/node&gt;
&lt;/node&gt;
</pre></div>
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