Package jakarta.xml.bind.annotation

Annotation Type XmlElementRef

  • @Retention(RUNTIME)
@Target({FIELD,METHOD})
public @interface XmlElementRef

    Maps a JavaBean property to an XML element derived from property's type.

    Usage

    @XmlElementRef annotation can be used with a JavaBean property or from within XmlElementRefs

    This annotation dynamically associates an XML element name with the JavaBean property. When a JavaBean property is annotated with XmlElement, the XML element name is statically derived from the JavaBean property name. However, when this annotation is used, the XML element name is derived from the instance of the type of the JavaBean property at runtime.

    XML Schema substitution group support

    XML Schema allows an XML document author to use XML element names that were not statically specified in the content model of a schema using substitution groups. Schema derived code provides support for substitution groups using an element property, (section 5.5.5, "Element Property" of Jakarta XML Binding specification). An element property method signature is of the form:

    An element factory method annotated with XmlElementDecl is used to create a JAXBElement instance, containing an XML element name. The presence of @XmlElementRef annotation on an element property indicates that the element name from JAXBElement instance be used instead of deriving an XML element name from the JavaBean property name.

    The usage is subject to the following constraints:

    • If the collection item type (for collection property) or property type (for single valued property) is JAXBElement, then @XmlElementRef.name() and @XmlElementRef.namespace() must point an element factory method with an @XmlElementDecl annotation in a class annotated with @XmlRegistry (usually ObjectFactory class generated by the schema compiler) :
      • @XmlElementDecl.name() must equal @XmlElementRef.name()
      • @XmlElementDecl.namespace() must equal @XmlElementRef.namespace().
    • If the collection item type (for collection property) or property type (for single valued property) is not JAXBElement, then the type referenced by the property or field must be annotated with XmlRootElement.
    • This annotation can be used with the following annotations: XmlElementWrapper, XmlJavaTypeAdapter.

    See "Package Specification" in jakarta.xml.bind.package javadoc for additional common information.

    Example 1: Ant Task Example

    The following Java class hierarchy models an Ant build script. An Ant task corresponds to a class in the class hierarchy. The XML element name of an Ant task is indicated by the XmlRootElement annotation on its corresponding class. {@snippet :
    Since:
    1.6, JAXB 2.0
    Author:
    • Kohsuke Kawaguchi, Sun Microsystems,Inc.
    • Sekhar Vajjhala, Sun Microsystems, Inc.
    See Also:
    XmlElementRefs

    • Optional Element Summary

      Optional Elements 
      Modifier and Type Optional Element Description
      java.lang.String name  
      java.lang.String namespace
      This parameter and name() are used to determine the XML element for the JavaBean property.
      boolean required
      Customize the element declaration to be required.
      java.lang.Class<?> type
      The Java type being referenced.

    • Element Detail

      • type

        java.lang.Class<?> type
        The Java type being referenced.

        If the value is DEFAULT.class, the type is inferred from the type of the JavaBean property.

        Default:
        jakarta.xml.bind.annotation.XmlElementRef.DEFAULT.class

      • namespace

        java.lang.String namespace
        This parameter and name() are used to determine the XML element for the JavaBean property.

        If type() is JAXBElement.class , then namespace() and name() point to a factory method with XmlElementDecl. The XML element name is the element name from the factory method's XmlElementDecl annotation or if an element from its substitution group (of which it is a head element) has been substituted in the XML document, then the element name is from the XmlElementDecl on the substituted element.

        If type() is not JAXBElement.class, then the XML element name is the XML element name statically associated with the type using the annotation XmlRootElement on the type. If the type is not annotated with an XmlElementDecl, then it is an error.

        If type() is not JAXBElement.class, then this value must be "".

        Default:
        ""

      • name

        java.lang.String name
        See Also:
        namespace()
        Default:
        "##default"

      • required

        boolean required
        Customize the element declaration to be required.

        If required() is true, then Javabean property is mapped to an XML schema element declaration with minOccurs="1". maxOccurs is "1" for a single valued property and "unbounded" for a multivalued property.

        If required() is false, then the Javabean property is mapped to XML Schema element declaration with minOccurs="0". maxOccurs is "1" for a single valued property and "unbounded" for a multivalued property.

        For compatibility with Jakarta XML Binding, this property defaults to true, despite the fact that XmlElement.required() defaults to false.

        Since:
        1.7, JAXB 2.2
        Default:
        true