XmlElementDecl (Java Platform SE 8 ) (original) (raw)

Maps a factory method to a XML element.

Usage

The annotation creates a mapping between an XML schema element declaration and a element factory method that returns a JAXBElement instance representing the element declaration. Typically, the element factory method is generated (and annotated) from a schema into the ObjectFactory class in a Java package that represents the binding of the element declaration's target namespace. Thus, while the annotation syntax allows @XmlElementDecl to be used on any method, semantically its use is restricted to annotation of element factory method. The usage is subject to the following constraints:

• The class containing the element factory method annotated with @XmlElementDecl must be marked with XmlRegistry.
• The element factory method must take one parameter assignable to Object.

Example 1: Annotation on a factory method

 // Example: code fragment
 @XmlRegistry
 class ObjectFactory {
     @XmlElementDecl(name="foo")
     JAXBElement<String> createFoo(String s) { ... }
 }

 <!-- XML input -->
   <foo>string

 // Example: code fragment corresponding to XML input
 JAXBElement o =
 (JAXBElement)unmarshaller.unmarshal(aboveDocument);
 // print JAXBElement instance to show values
 System.out.println(o.getName());   // prints  "{}foo"
 System.out.println(o.getValue());  // prints  "string"
 System.out.println(o.getValue().getClass()); // prints "java.lang.String"

 <!-- Example: XML schema definition -->
 <xs:element name="foo" type="xs:string"/>

Example 2: Element declaration with non local scope

The following example illustrates the use of scope annotation parameter in binding of element declaration in schema derived code.

The following example may be replaced in a future revision of this javadoc.

 <!-- Example: XML schema definition -->
 <xs:schema>
   <xs:complexType name="pea">
     <xs:choice maxOccurs="unbounded">
       <xs:element name="foo" type="xs:string"/>
       <xs:element name="bar" type="xs:string"/>
     </xs:choice>
   </xs:complexType>
   <xs:element name="foo" type="xs:int"/>
 </xs:schema>

 // Example: expected default binding
 class Pea {
     @XmlElementRefs({
         @XmlElementRef(name="foo",type=JAXBElement.class)
         @XmlElementRef(name="bar",type=JAXBElement.class)
     })
     List<JAXBElement<String>> fooOrBar;
 }

 @XmlRegistry
 class ObjectFactory {
     @XmlElementDecl(scope=Pea.class,name="foo")
     JAXBElement createPeaFoo(String s);

     @XmlElementDecl(scope=Pea.class,name="bar")
     JAXBElement createPeaBar(String s);

     @XmlElementDecl(name="foo")
     JAXBElement createFoo(Integer i);
 }

Without scope createFoo and createPeaFoo would become ambiguous since both of them map to a XML schema element with the same local name "foo".