XmlRootElement (Java Platform SE 7 ) (original) (raw)

Maps a class or an enum type to an XML element.

Usage

The @XmlRootElement annotation can be used with the following program elements:

• a top level class
• an enum type

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

When a top level class or an enum type is annotated with the @XmlRootElement annotation, then its value is represented as XML element in an XML document.

This annotation can be used with the following annotations:XmlType, XmlEnum, XmlAccessorType,XmlAccessorOrder.

Example 1: Associate an element with XML Schema type

 // Example: Code fragment
 @XmlRootElement
 class Point {
    int x;
    int y;
    Point(int _x,int _y) {x=_x;y=_y;}
 }

 //Example: Code fragment corresponding to XML output
 marshal( new Point(3,5), System.out);

 <!-- Example: XML output -->
 <point>
   <x> 3 
   <y> 5 
 </point>

The annotation causes an global element declaration to be produced in the schema. The global element declaration is associated with the XML schema type to which the class is mapped.

 <!-- Example: XML schema definition -->
 <xs:element name="point" type="point"/>
 <xs:complexType name="point">
   <xs:sequence>
     <xs:element name="x" type="xs:int"/>
     <xs:element name="y" type="xs:int"/>
   </xs:sequence>
 </xs:complexType>

Example 2: Orthogonality to type inheritance

An element declaration annotated on a type is not inherited by its derived types. The following example shows this.

 // Example: Code fragment
 @XmlRootElement
 class Point3D extends Point {
     int z;
     Point3D(int _x,int _y,int _z) {super(_x,_y);z=_z;}
 }

 //Example: Code fragment corresponding to XML output *
 marshal( new Point3D(3,5,0), System.out );

 <!-- Example: XML output -->
 <!-- The element name is point3D not point -->
 <point3D>
   <x>3</x>
   <y>5</y>
   <z>0</z>
 </point3D>

 <!-- Example: XML schema definition -->
 <xs:element name="point3D" type="point3D"/>
 <xs:complexType name="point3D">
   <xs:complexContent>
     <xs:extension base="point">
       <xs:sequence>
         <xs:element name="z" type="xs:int"/>
       </xs:sequence>
     </xs:extension>
   </xs:complexContent>
 </xs:complexType>

Example 3: Associate a global element with XML Schema type to which the class is mapped.

 //Example: Code fragment
 @XmlRootElement(name="PriceElement")
 public class USPrice {
     @XmlElement
     public java.math.BigDecimal price;
 }

 <!-- Example: XML schema definition -->
 <xs:element name="PriceElement" type="USPrice"/>
 <xs:complexType name="USPrice">
   <xs:sequence>
     <xs:element name="price" type="xs:decimal"/>
   </sequence>
 </xs:complexType>