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

• 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: {@link XmlElement}, {@link XmlAttribute}, {@link XmlList}, and {@link 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>