JAXB & Namespaces

The majority of XML documents are namespace qualified, yet most XML binding examples do not demonstrate namespaces (sometimes because the XML binding solution does not support them). In this post I'll demonstrate how easy namespace handling is using JAXB.


We'll start with a Customer class that has no namespace information specified:

package example;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Customer {

    private long id;
    private String name;

    @XmlAttribute
    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

The following code will be used to run this example:

package example;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = 
           JAXBContext.newInstance(Customer.class);

        Customer customer = new Customer();
        customer.setId(123);
        customer.setName("Jane Doe");

        Marshaller m = jc.createMarshaller();
        m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        m.marshal(customer, System.out);
    }
}

Running the example at this point will produce the following XML:

<customer id="123">
    <name>Jane Doe</name>
</customer>

Package Level Metadata

We can easily qualify all the elements through the use of the package level annotation @XmlSchema.  To specify a package level annotation, create a class called package-info in the desired package (see complete source below for an example).  Below we will set a default namespace and specify that by default all elements are namespace qualified.

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

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

This will produce the following XML:

<customer 
    xmlns="http://www.example.org/package" 
    id="123">
    <name>Jane Doe</name>
</customer>

Type Level Metadata

You can override the package level namespace information at the type level using the @XmlType annotation.  As per the @XmlSchema annotation elements are still namespace qualified by default, only now the elements inside the Customer type will be qualified with the namespace http://www.example.org/type.

package example;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlRootElement
@XmlType(namespace="http://www.example.org/type")
public class Customer {

    private long id;
    private String name;

    @XmlAttribute
    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

This will produce the following output:

<ns2:customer 
    xmlns="http://www.example.org/type" 
    xmlns:ns2="http://www.example.org/package" 
    id="123">
    <name>Jane Doe</name>
</ns2:customer>

Field/Property Level Metadata

You can also control namespaces at the property/field level.  All of the annotations related to attributes and elements have a namespace parameter.

package example;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlRootElement
@XmlType(namespace="http://www.example.org/type")
public class Customer {

    private long id;
    private String name;

    @XmlAttribute
    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    @XmlElement(namespace="http://www.example.org/property")
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

This will produce the following output:

<ns2:customer 
    xmlns="http://www.example.org/property" 
    xmlns:ns2="http://www.example.org/package"
    id="123">
    <name>Jane Doe</name>
</ns2:customer>

Namespace handling in JAXB is easy.  For most documents the package level annotation is all you need.  Then you can use the other levels to customize your document.