XmlIDREF (Java EE 6 )

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SUMMARY: REQUIRED | OPTIONAL

DETAIL: ELEMENT

javax.xml.bind.annotation
Annotation Type XmlIDREF

@Retention(value=RUNTIME) @Target(value={FIELD,METHOD}) public @interface XmlIDREF

Maps a JavaBean property to XML IDREF.

To preserve referential integrity of an object graph across XML serialization followed by a XML deserialization, requires an object reference to be marshalled by reference or containment appropriately. Annotations @XmlID and @XmlIDREF together allow a customized mapping of a JavaBean property's type by containment or reference.

Usage

The @XmlIDREF annotation can be used with the following program elements:

a JavaBean property
non static, non transient field

See "Package Specification" in javax.xml.bind.package javadoc for additional common information.

The usage is subject to the following constraints:

If the type of the field or property is a collection type, then the collection item type must contain a property or field annotated with @XmlID.
If the field or property is single valued, then the type of the property or field must contain a property or field annotated with @XmlID.
Note: If the collection item type or the type of the property (for non collection type) is java.lang.Object, then the instance must contain a property/field annotated with @XmlID attribute.
This annotation can be used with the following annotations: XmlElement, XmlAttribute, XmlList, and XmlElements.

Example: Map a JavaBean property to xs:IDREF (i.e. by reference rather than by containment)

 //EXAMPLE: Code fragment
 public class Shipping {
 @XmlIDREF public Customer getCustomer();
 public void setCustomer(Customer customer);
 ....
 }
 <!-- Example: XML Schema fragment -->
 <xs:complexType name="Shipping">
 <xs:complexContent>
 <xs:sequence>
 <xs:element name="customer" type="xs:IDREF"/>
 ....
 </xs:sequence>
 </xs:complexContent>
 </xs:complexType>

Example 2: The following is a complete example of containment versus reference.

 // By default, Customer maps to complex type xs:Customer
 public class Customer {
 
 // map JavaBean property type to xs:ID
 @XmlID public String getCustomerID();
 public void setCustomerID(String id);
 // .... other properties not shown 
 }
 // By default, Invoice maps to a complex type xs:Invoice 
 public class Invoice {
 
 // map by reference
 @XmlIDREF public Customer getCustomer(); 
 public void setCustomer(Customer customer);
 // .... other properties not shown here
 }
 // By default, Shipping maps to complex type xs:Shipping
 public class Shipping {
 // map by reference
 @XmlIDREF public Customer getCustomer(); 
 public void setCustomer(Customer customer);
 }
 // at least one class must reference Customer by containment;
 // Customer instances won't be marshalled.
 @XmlElement(name="CustomerData")
 public class CustomerData {
 // map reference to Customer by containment by default.
 public Customer getCustomer();
 // maps reference to Shipping by containment by default. 
 public Shipping getShipping(); 
 // maps reference to Invoice by containment by default. 
 public Invoice getInvoice(); 
 }
 <!-- XML Schema mapping for above code frament -->
 <xs:complexType name="Invoice">
 <xs:complexContent>
 <xs:sequence>
 <xs:element name="customer" type="xs:IDREF"/>
 ....
 </xs:sequence>
 </xs:complexContent>
 </xs:complexType>
 <xs:complexType name="Shipping">
 <xs:complexContent>
 <xs:sequence>
 <xs:element name="customer" type="xs:IDREF"/>
 ....
 </xs:sequence>
 </xs:complexContent>
 </xs:complexType>
 <xs:complexType name="Customer">
 <xs:complexContent>
 <xs:sequence>
 ....
 </xs:sequence>
 <xs:attribute name="CustomerID" type="xs:ID"/>
 </xs:complexContent>
 </xs:complexType>
 <xs:complexType name="CustomerData">
 <xs:complexContent>
 <xs:sequence>
 <xs:element name="customer" type="xs:Customer"/>
 <xs:element name="shipping" type="xs:Shipping"/>
 <xs:element name="invoice" type="xs:Invoice"/>
 </xs:sequence>
 </xs:complexContent>
 </xs:complexType>
 <xs:element name"customerData" type="xs:CustomerData"/>
 <!-- Instance document conforming to the above XML Schema -->
 <customerData>
 <customer customerID="Alice">
 ....
 </customer>
 <shipping customer="Alice">
 ....
 </shipping>
 
 <invoice customer="Alice">
 ....
 </invoice>
 </customerData>

Example 3: Mapping List to repeating element of type IDREF

 // Code fragment
 public class Shipping {
 @XmlIDREF
 @XmlElement(name="Alice")
 public List customers;
 }
 <!-- XML schema fragment -->
 <xs:complexType name="Shipping">
 <xs:sequence>
 <xs:choice minOccurs="0" maxOccurs="unbounded">
 <xs:element name="Alice" type="xs:IDREF"/>
 </xs:choice>
 </xs:sequence>
 </xs:complexType>

Example 4: Mapping a List to a list of elements of type IDREF.

 //Code fragment
 public class Shipping {
 @XmlIDREF
 @XmlElements(
 @XmlElement(name="Alice", type="Customer.class")
 @XmlElement(name="John", type="InternationalCustomer.class")
 public List customers;
 }
 <!-- XML Schema fragment -->
 <xs:complexType name="Shipping">
 <xs:sequence>
 <xs:choice minOccurs="0" maxOccurs="unbounded">
 <xs:element name="Alice" type="xs:IDREF"/>
 <xs:element name="John" type="xs:IDREF"/>
 </xs:choice>
 </xs:sequence>
 </xs:complexType>

Since:: JAXB2.0
Author:: Sekhar Vajjhala, Sun Microsystems, Inc.
See Also:: XmlID