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Revision as of 11:37, 29 June 2011
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Mapping Single Key Relationships
To model non-privately-owned relationships, your "target" objects must have IDs (keys) defined, and your "source" object must use these IDs to map the relationship.
Relationships represented with keys use the @XmlID and @XmlIDREF annotations. Although the JAXB specification requires that the property marked with @XmlID be a String, MOXy JAXB does not enforce this restriction.
In this example, each Employee has one manager but multiple reports.
package example; import javax.xml.bind.annotation.*; @XmlAccessorType(XmlAccessType.FIELD) public class Employee { @XmlAttribute @XmlID private Integer id; @XmlAttribute private String name; @XmlIDREF private Employee manager; @XmlElement(name="report") @XmlIDREF private List<Employee> reports; ... }
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" type="java.lang.Integer" xml-id="true"/> <xml-attribute java-attribute="name" type="java.lang.String"/> <xml-element java-attribute="manager" type="mypackage.Employee" xml-idref="true"/> <xml-element java-attribute="reports" type="mypackage.Employee" container-type="java.util.ArrayList" xml-idref="true"/> </java-attributes> </java-type> ...
This would produce the following XML:
<company> <employee id="1" name="Jane Doe"> <report>2</report> <report>3</report> </employee> <employee id="2" name="John Smith"> <manager>1</manager> </employee> <employee id="3" name="Anne Jones"> <manager>1</manager> </employee> </company>
The manager and reports elements contain the IDs of the Employee instances they are referencing.
Using @XmlList
Because the @XmlIDREF annotation is also compatible with the @XmlList annotation, the Employee object could be modeled as:
package example; import javax.xml.bind.annotation.*; @XmlAccessorType(XmlAccessType.FIELD) public class Employee { @XmlID @XmlAttribute private Integer id; @XmlAttribute private String name; @XmlIDREF private Employee manager; @XmlIDREF @XmlList private List<Employee> reports; ... }
This would produce the following XML:
<company> <employee id="1" name="Jane Doe"> <reports>2 3</reports> </employee> <employee id="2" name="John Smith"> <manager>1</manager> </employee> <employee id="3" name="Anne Jones"> <manager>1</manager> </employee> </company>