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Difference between revisions of "EclipseLink/UserGuide/MOXy/Relationships/Shared Reference/Keys and Foreign Keys/Composite Key"
| Line 19: | Line 19: | ||
<source lang="java"> | <source lang="java"> | ||
| + | package example; | ||
| + | |||
| + | import javax.xml.bind.annotation.*; | ||
| + | import org.eclipse.persistence.oxm.annotations.*; | ||
| + | |||
@XmlAccessorType(XmlAccessType.FIELD) | @XmlAccessorType(XmlAccessType.FIELD) | ||
public class Employee { | public class Employee { | ||
Revision as of 13:01, 20 April 2011
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Key API
Mapping Composite Key Relationships
If the objects that you want to map have multi-part keys (i.e., a combination of fields that determines uniqueness), you can use EclipseLink's @XmlKey and @XmlJoinNodes to set up this relationship.
One or more @XmlKey annotations can be used to declare the primary keys in a given class. For a single key, either @XmlID or @XmlKey can be used. For composite primary keys, multiple @XmlKey annotations can be used, or a single @XmlID can be combined with one or more @XmlKey annotations.
In this example, each Employee has one manager but multiple reports, and Employees are uniquely identified by the combination of their id and name fields.
package example; import javax.xml.bind.annotation.*; import org.eclipse.persistence.oxm.annotations.*; @XmlAccessorType(XmlAccessType.FIELD) public class Employee { @XmlID @XmlAttribute private Integer id; @XmlKey @XmlAttribute private String name; @XmlJoinNodes( { @XmlJoinNode(xmlPath = "manager/@id", referencedXmlPath = "@id"), @XmlJoinNode(xmlPath = "manager/@name", referencedXmlPath = "@name") }) public Employee manager; @XmlJoinNodes( { @XmlJoinNode(xmlPath = "report/@id", referencedXmlPath = "@id"), @XmlJoinNode(xmlPath = "report/@name", referencedXmlPath = "@name") }) public List<Employee> reports = new ArrayList<Employee>(); ... }
The following example shows how to define this mapping information in EclipseLink's OXM metadata format.
... <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> ...
This would produce the following XML:
<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>
