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

• 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>