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* accompanied this code).
*
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package javax.xml.bind.annotation;
import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;
/**
* <p>
* Maps a JavaBean property to XML IDREF.
*
* <p>
* To preserve referential integrity of an object graph across XML
* serialization followed by a XML deserialization, requires an object
* reference to be marshaled by reference or containment
* appropriately. Annotations {@code @XmlID} and {@code @XmlIDREF}
* together allow a customized mapping of a JavaBean property's
* type by containment or reference.
*
* <p><b>Usage</b> </p>
* The {@code @XmlIDREF} annotation can be used with the following
* program elements:
* <ul>
* <li> a JavaBean property </li>
* <li> non static, non transient field </li>
* </ul>
*
* <p>See "Package Specification" in javax.xml.bind.package javadoc for
* additional common information.</p>
*
* <p> The usage is subject to the following constraints:
* <ul>
*
* <li> 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 {@code @XmlID}. </li>
* <li> If the field or property is single valued, then the type of
* the property or field must contain a property or field
* annotated with {@code @XmlID}.
* <p>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
* {@code @XmlID} attribute.
* </li>
* <li> This annotation can be used with the following annotations:
* {@link XmlElement}, {@link XmlAttribute}, {@link XmlList},
* and {@link XmlElements}.</li>
*
* </ul>
* <p><b>Example:</b> Map a JavaBean property to {@code xs:IDREF}
* (i.e. by reference rather than by containment)</p>
* <pre>
*
* //EXAMPLE: Code fragment
* public class Shipping {
* @XmlIDREF public Customer getCustomer();
* public void setCustomer(Customer customer);
* ....
* }
* {@code
*
* <!-- 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>
*
* }</pre>
*
*
* <p><b>Example 2: </b> The following is a complete example of
* containment versus reference.
*
* <pre>
* // 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();
* }
* {@code
*
* <!-- 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>
*
* }</pre>
*
* <p><b>Example 3: </b> Mapping List to repeating element of type IDREF
* <pre>
* // Code fragment
* public class Shipping {
* @XmlIDREF
* @XmlElement(name="Alice")
* public List customers;
* }
* {@code
*
* <!-- 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>
* }</pre>
*
* <p><b>Example 4: </b> Mapping a List to a list of elements of type IDREF.
* <pre>
* //Code fragment
* public class Shipping {
* @XmlIDREF
* @XmlElements(
* @XmlElement(name="Alice", type="Customer.class")
* @XmlElement(name="John", type="InternationalCustomer.class")
* public List customers;
* }
* {@code
*
* <!-- 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>
* }</pre>
* @author Sekhar Vajjhala, Sun Microsystems, Inc.
* @see XmlID
* @since 1.6, JAXB 2.0
*/
@Retention(RUNTIME) @Target({FIELD, METHOD})
public @interface XmlIDREF {}