/*
 * Copyright (c) 2004, 2020 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0, which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package jakarta.xml.bind.annotation;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.RetentionPolicy.RUNTIME;
import static java.lang.annotation.ElementType.TYPE;

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 jakarta.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 </x>
      <y> 5 </y>
    </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>
Author:Sekhar Vajjhala, Sun Microsystems, Inc.
Since:1.6, JAXB 2.0
/** * Maps a class or an enum type to an XML element. * * <p> <b>Usage</b> </p> * <p> * The &#64;XmlRootElement annotation can be used with the following program * elements: * <ul> * <li> a top level class </li> * <li> an enum type </li> * </ul> * * <p>See "Package Specification" in jakarta.xml.bind.package javadoc for * additional common information.</p> * * <p> * When a top level class or an enum type is annotated with the * &#64;XmlRootElement annotation, then its value is represented * as XML element in an XML document. * * <p> This annotation can be used with the following annotations: * {@link XmlType}, {@link XmlEnum}, {@link XmlAccessorType}, * {@link XmlAccessorOrder}. * </p> * <p> * <b>Example 1: </b> Associate an element with XML Schema type * <pre> * // Example: Code fragment * &#64;XmlRootElement * class Point { * int x; * int y; * Point(int _x,int _y) {x=_x;y=_y;} * } * </pre> * * <pre> * //Example: Code fragment corresponding to XML output * marshal( new Point(3,5), System.out); * </pre> * * <pre>{@code * * <!-- Example: XML output --> * <point> * <x> 3 </x> * <y> 5 </y> * </point> * }</pre> * * 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. * * <pre>{@code * * <!-- 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> * }</pre> * * <p> * * <b>Example 2: Orthogonality to type inheritance </b> * * <p> * An element declaration annotated on a type is not inherited by its * derived types. The following example shows this. * <pre> * // Example: Code fragment * &#64;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 ); * {@code * * <!-- 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> * }</pre> * * <b>Example 3: </b> Associate a global element with XML Schema type * to which the class is mapped. * <pre> * //Example: Code fragment * &#64;XmlRootElement(name="PriceElement") * public class USPrice { * &#64;XmlElement * public java.math.BigDecimal price; * } * {@code * * <!-- 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> * }</pre> * * @author Sekhar Vajjhala, Sun Microsystems, Inc. * @since 1.6, JAXB 2.0 */
@Retention(RUNTIME) @Target({TYPE}) public @interface XmlRootElement {
namespace name of the XML element.

If the value is "##default", then the XML namespace name is derived from the package of the class ( XmlSchema ). If the package is unnamed, then the XML namespace is the default empty namespace.

/** * namespace name of the XML element. * <p> * If the value is "##default", then the XML namespace name is derived * from the package of the class ( {@link XmlSchema} ). If the * package is unnamed, then the XML namespace is the default empty * namespace. */
String namespace() default "##default";
local name of the XML element.

If the value is "##default", then the name is derived from the class name.

/** * local name of the XML element. * <p> * If the value is "##default", then the name is derived from the * class name. * */
String name() default "##default"; }