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| <b>Release 2.7</b><br /></font></td> |
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| <div class="sect1"><!-- infolevel="all" infotype="General" --> |
| <h1 class="sect1"><font face="arial, helvetica, sans-serif" color="#330099">Mapping Composite Key Relationships</font></h1> |
| <p>If the objects that you want to map have multi-part keys (that is, a combination of fields that determines uniqueness), you can use EclipseLink's <code>@XmlKey</code> and <code>@XmlJoinNodes</code> to set up this relationship.</p> |
| <p>One or more <code>@XmlKey</code> annotations can be used to declare the primary keys in a given class. For a single key, either <code>@XmlID</code> or <code>@XmlKey</code> can be used. For composite primary keys, multiple <code>@XmlKey</code> annotations can be used, or a single <code>@XmlID</code> can be combined with one or more <code>@XmlKey</code> annotations.</p> |
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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>Composite Keys can be useful when using JAXB to map JPA entities. For more information see Converting JPA entities to/from XML (via JAXB).</p> |
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| <p>In <a href="#BABHFBDI">Example 7-8</a>, each <strong>Employee</strong> has one <strong>manager</strong> but multiple <strong>reports</strong>, and <strong>Employees</strong> are uniquely identified by the combination of their <code>id</code> and <code>name</code> fields.</p> |
| <div class="example"><a id="BABHFBDI" name="BABHFBDI"></a><a id="TLJAX356" name="TLJAX356"></a> |
| <p><strong><em><font face="arial, helvetica, sans-serif">Example 7-8 Using the @XmlKey and @XmlJoinNodes Annotations</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.*; |
| |
| @XmlAccessorType(XmlAccessType.FIELD) |
| public class Employee { |
| @XmlID |
| @XmlAttribute |
| private Integer id; |
| |
| <strong>@XmlKey</strong> |
| @XmlAttribute |
| private String name; |
| |
| <strong>@XmlJoinNodes</strong>( { |
| @XmlJoinNode(xmlPath = "manager/@id", referencedXmlPath = "@id"), |
| @XmlJoinNode(xmlPath = "manager/@name", referencedXmlPath = "@name") }) |
| public Employee manager; |
| |
| <strong>@XmlJoinNodes</strong>( { |
| @XmlJoinNode(xmlPath = "report/@id", referencedXmlPath = "@id"), |
| @XmlJoinNode(xmlPath = "report/@name", referencedXmlPath = "@name") }) |
| public List<Employee> reports = new ArrayList<Employee>(); |
| |
| ... |
| } |
| |
| </pre></div> |
| <!-- class="example" --> |
| <p><a href="#BABHAEGF">Example 7-9</a> shows how to define this mapping information in EclipseLink's OXM metadata format.</p> |
| <div class="example"><a id="BABHAEGF" name="BABHAEGF"></a><a id="TLJAX357" name="TLJAX357"></a> |
| <p><strong><em><font face="arial, helvetica, sans-serif">Example 7-9 Sample XML Mapping</font></em></strong></p> |
| <pre xml:space="preserve" class="oac_no_warn"> |
| ... |
| <java-type name="Employee"> |
| <java-attributes> |
| <xml-attribute java-attribute="id" xml-id="true" /> |
| <xml-attribute java-attribute="name" xml-key="true" /> |
| <xml-join-nodes java-attribute="manager"> |
| <xml-join-node xml-path="manager/@id" referenced-xml-path="@id" /> |
| <xml-join-node xml-path="manager/@name" referenced-xml-path="@name" /> |
| </xml-join-nodes> |
| <xml-join-nodes java-attribute="reports" container-type="java.util.ArrayList"> |
| <xml-join-node xml-path="report/@id" referenced-xml-path="@id" /> |
| <xml-join-node xml-path="report/@name" referenced-xml-path="@name" /> |
| </xml-join-nodes> |
| </java-attributes> |
| </java-type> |
| ... |
| |
| </pre></div> |
| <!-- class="example" --> |
| <p>This would produce the following XML:</p> |
| <pre xml:space="preserve" class="oac_no_warn"> |
| <company> |
| <employee id="1" name="Jane Doe"> |
| <report id="2" name="John Smith"/> |
| <report id="3" name="Anne Jones"/> |
| </employee> |
| <employee id="2" name="John Smith"> |
| <manager id="1" name="Jane Doe"/> |
| </employee> |
| <employee id="3" name="Anne Jones"> |
| <manager id="1" name="Jane Doe"/> |
| </employee> |
| </company> |
| </pre></div> |
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