Team lead for the TopLink/EclipseLink JAXB & SDO implementations, and the Oracle representative on those specifications. Blaise is a DZone MVB and is not an employee of DZone and has posted 44 posts at DZone. You can read more from them at their website. View Full User Profile

JAXB and Package Level XmlAdapters

02.23.2012
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The XmlAdapter mechanism in JAXB (JSR-222) allows an unmappable class to be converted to a mappable one.  An XmlAdapter can be registered with the @XmlJavaTypeAdapter at the field, property, type, or package level.  This post will focus on the scope of the XmlAdapter when registered at the package level.


Package 1 - xmladapter.bar

package-info

When an XmlAdapter is registered at the package level it must include the type parameter.  The type parameter specifies the Java class that this XmlAdapter will be applied to.  For this package (xmladapter.bar) we will specify an XmlAdapter (StringAdapter) that will be applied to all fields/properties of type String within this package.

@XmlJavaTypeAdapters({
    @XmlJavaTypeAdapter(value=StringAdapter.class, type=String.class)
})
package xmladapter.bar;

import javax.xml.bind.annotation.adapters.*; 

StringAdapter

Our XmlAdapter will simply convert all instances of String to upper case when marshalling:

package xmladapter.bar;

import javax.xml.bind.annotation.adapters.XmlAdapter;

public class StringAdapter extends XmlAdapter<String, String> {

    @Override
    public String unmarshal(String v) throws Exception {
        return v;
    }

    @Override
    public String marshal(String v) throws Exception {
        if(null == v) {
            return v;
        }
        return v.toUpperCase();
    }

}

Bar

Bar represents a POJO in this package with a property (name) of type String:

package xmladapter.bar;

public class Bar {

    private String name;

    public String getName() {
        return name;
    }

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

}

Package 2 - xmladapter.foo

Foo

Foo represents a domain object with a property of type String that exists in a different package (xmladapter.foo). The XmlAdapter we registered for the xmladapter.bar package will not apply to String fields/properties on this class:

package xmladapter.foo;

import javax.xml.bind.annotation.*;
import xmladapter.bar.Bar;

@XmlRootElement
@XmlType(propOrder={"name", "bar"})
public class Foo {

    private String name;
    private Bar bar;

    public String getName() {
        return name;
    }

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

    public Bar getBar() {
        return bar;
    }

    public void setBar(Bar bar) {
        this.bar = bar;
    }

}

Demo

The following code will create instances of both Foo and Bar and marshal them to XML.  Note how the values set on the name properties for both Foo and Bar are lower case:

package xmladapter;

import javax.xml.bind.*;
import xmladapter.bar.Bar;
import xmladapter.foo.Foo;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Foo.class, Bar.class);
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

        Foo foo = new Foo();
        foo.setName("foo");

        Bar bar = new Bar();
        bar.setName("bar");
        foo.setBar(bar);
 
        marshaller.marshal(foo, System.out);
    }

}

Output

Notice how the value of the name element within bar has been converted to upper case (line 5), but he name element within foo has not (line 3):

<?xml version="1.0" encoding="UTF-8"?>
<foo>
    <name>foo</name>
    <bar>
        <name>BAR</name>
    </bar>
</foo>

 

From http://blog.bdoughan.com/2012/02/jaxb-and-package-level-xmladapters.html

Published at DZone with permission of Blaise Doughan, author and DZone MVB.

(Note: Opinions expressed in this article and its replies are the opinions of their respective authors and not those of DZone, Inc.)

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Comments

Goel Yatendra replied on Thu, 2012/03/15 - 3:38pm

I have enjoyed following your blog for a while... it's very informative. For the first time, I need an XMLAdapter and I can see how to do it if we start from Java classes that we can add annotations to. But how to get those annotations if we start from XSD and use xjc to generate the model.

Blaise Doughan replied on Fri, 2012/06/22 - 3:05pm in response to: Goel Yatendra

Hi Goel,

Here is a link to an article I wrote that explains how to leverage XmlAdapters when starting from an XSD:

-Blaise

David Chu replied on Thu, 2012/12/20 - 3:48pm

 Very informative article.  Thank you

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