Understanding JAXB @XmlRootElement annotation

Question

I am using the tutorial here for understanding JAXB.

When the writer comes to create the root of the document, the writer begins as below:

//This sta         


        

Answer 1

• @XmlRootElement annotation can be used to map a class or enum type to XML type.

• 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.

• Follow the example given below to get more idea:

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>

Answer 2

I recommend using the package level @XmlSchema annotation to specify the namespace qualification for you model. A package level annotation goes in a special class called package-info that contains the exact content as shown below. That annotation will mean that all elements in your document without an explicit namespace given will use that namespace.

org/example/foo/package-info.java

@XmlSchema(
    namespace = "http://www.example.org/foo",
    elementFormDefault = XmlNsForm.QUALIFIED)
package org.example.foo;

import javax.xml.bind.annotation.XmlNsForm;
import javax.xml.bind.annotation.XmlSchema;

Overriding the Namespace

• You can override the namespace given in the @XmlSchema for all properties in a class using the @XmlType annotation.
• You can override the namespace for a given element using the namespace property on the @XmlRootElement or @XmlElement annotation.

For More Information

• http://blog.bdoughan.com/2010/08/jaxb-namespaces.html
• http://blog.bdoughan.com/2012/07/jaxb-and-root-elements.html