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

XML Schema to Java - Generating XmlAdapters

12.30.2011
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In previous posts I have demonstrated how powerful JAXB's XmlAdapter can be when starting from domain objects.  In this example I will demonstrate how to leverage an XmlAdapter when generating an object model from an XML schema.  This post was inspired by an answer I gave to a question on Stack Overflow (feel free to up vote).


XMLSchema (format.xsd)
The following is the XML schema that will be used for this example.  The interesting portion is a type called NumberCodeValueType.  This type has a specified pattern requiring it be a seven digit number.  This number can have leading zeros which would not be marshalled by JAXB's default conversion of numbers.
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
 
    <xs:element name="root">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="number" type="NumberCodeValueType" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>
 
    <xs:simpleType name="NumberCodeValueType">
        <xs:restriction base="xs:int">
            <xs:pattern value="[0-7]{7}" />
        </xs:restriction>
    </xs:simpleType>
 
</xs:schema>

NumberFormatter
Since JAXB's default number to String algorithm will not match our schema requirements, we will need to write our own formatter.  We are required to provide two static methods one that coverts our type to the desired XML format, and another that converts from the XML format.
package blog.xmladapter.bindings;
 
public class NumberFormatter {
 
    public static String printInt(Integer value) {
        String result = String.valueOf(value);
        for(int x=0, length = 7 - result.length(); x<length; x++) {
            result = "0" + result;
        }
        return result;
    }
 
    public static Integer parseInt(String value) {
        return Integer.valueOf(value);
    }
 
}

bindings.xml
We will leverage a JAXB bindings file to reference the formatter:
<jxb:bindings xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:jxb="http://java.sun.com/xml/ns/jaxb" version="2.1">
    <jxb:bindings schemaLocation="format.xsd">
        <jxb:bindings node="//xs:element[@name='number']">
            <jxb:property>
                <jxb:baseType>
                    <jxb:javaType name="java.lang.Integer"
                        parseMethod="blog.xmladapter.bindings.NumberFormatter.parseInt"
                        printMethod="blog.xmladapter.bindings.NumberFormatter.printInt" />
                </jxb:baseType>
            </jxb:property>
        </jxb:bindings>
    </jxb:bindings>
</jxb:bindings>


XJC Call
The bindings file is referenced in the XJC call as:
xjc -d out -p blog.xmladapter.bindings -b bindings.xml format.xsd


Adapter1
This will cause an XmlAdapter to be created that leverages the formatter:
package blog.xmladapter.bindings;
 
import javax.xml.bind.annotation.adapters.XmlAdapter;
 
public class Adapter1 extends XmlAdapter<String, Integer> {
 
    public Integer unmarshal(String value) {
        return (blog.xmladapter.bindings.NumberFormatter.parseInt(value));
    }
 
    public String marshal(Integer value) {
        return (blog.xmladapter.bindings.NumberFormatter.printInt(value));
    }
 
}


Root
The XmlAdapter will be referenced from the domain object using the @XmlJavaTypeAdapter annotation:
package blog.xmladapter.bindings;
 
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
 
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
    "number"
})
@XmlRootElement(name = "root")
public class Root {
 
    @XmlElement(required = true, type = String.class)
    @XmlJavaTypeAdapter(Adapter1 .class)
    protected Integer number;
 
    public Integer getNumber() {
        return number;
    }
 
    public void setNumber(Integer value) {
        this.number = value;
    }
 
}


Demo
Now if we run the following demo code:
package blog.xmladapter.bindings;
 
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(Root.class);
 
        Root root = new Root();
        root.setNumber(4);
 
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(root, System.out);
    }
}


Output
We will get the desired output:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root>
    <number>0000004</number>
</root>

 

From http://blog.bdoughan.com/2011/08/xml-schema-to-java-generating.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

Afandi Merathi replied on Sun, 2012/03/18 - 7:52am

Hi Blaise, question, why is it necessary to add a "name" attribute to the jxb:javaType element in the bindings.xml file? What's it for? Thanks!

Blaise Doughan replied on Fri, 2012/06/22 - 3:02pm in response to: Afandi Merathi

Hi Afandi,

 The "name" attribute on the "jxb:javaType" element specifies the type of the generated field/property, and is required according to the XML schema for the bindings document.  We need to specify it since the print/parse methods are not required to be on the classpath to infer the types from.

-Blaise

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