javax.xml.bind.annotation

Annotation Type XmlIDREF

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

将JavaBean属性映射到XML IDREF。

为了保持XML序列化之后的XML反序列化对象图的引用完整性，需要通过引用或遏制来对对象引用进行编组。 注释@XmlID和@XmlIDREF一起允许通过遏制或引用定制映射JavaBean属性的类型。

用法

@XmlIDREF注释可以与以下程序元素一起使用：

• 一个JavaBean属性
• 非静态，非瞬态场

有关其他常见信息，请参阅javax.xml.bind.package javadoc中的“Package Specification”。

用法受以下限制：

• 如果字段或属性的类型是集合类型，则集合项类型必须包含一个注释为@XmlID的属性或字段。
• 如果字段或属性是单值，则属性或字段的类型必须包含用@XmlID注释的属性或字段。

  注意：如果集合项目类型或属性类型（对于非集合类型）为java.lang.Object，则该实例必须包含带有@XmlID属性注释的属性/字段。

• 此注释可与以下注释一起使用： XmlElement ， XmlAttribute ， XmlList和XmlElements 。

示例：将JavaBean属性映射到xs:IDREF （即通过引用而不是通过遏制）

  //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> 

示例2：以下是遏制与参考的完整示例。

  // 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> 

示例3：将列表映射到IDREF类型的重复元素

  // 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> 

示例4：将列表映射到IDREF类型的元素列表。

  //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> 

从以下版本开始：

JAXB2.0

另请参见：

XmlID