Module jakarta.xml.bind

Package jakarta.xml.bind.annotation

Annotation Type XmlIDREF

@Retention(RUNTIME)
@Target({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 an XML deserialization, requires an object reference to be marshaled 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 jakarta.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 {@code xs:Customer}
 public class Customer {

     // map JavaBean property type to {@code xs:ID}
     @XmlID public String getCustomerID();
     public void setCustomerID(String id);

     // .... other properties not shown
 }

 // By default, Invoice maps to a complex type {@code 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 {@code 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 fragment -->

 <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
     @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>

Author:

Sekhar Vajjhala, Sun Microsystems, Inc.

See Also:

• XmlID