Using JAXB generated class for an element that requires an integer with a pattern

You could do the following:

NumberFormatter

You can do this by writing your own formatter:

package forum7182533;

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);
    }

}

XMLSchema (format.xsd)

Then when you are going to generate your classes from your XML Schema:

<?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>

bindings.xml

You will leverage a JAXB bindings file to reference your 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:simpleType[@name="NumberCodeValueType"]" -->
        <jxb:bindings node="//xs:element[@name="number"]">
            <jxb:property>
                <jxb:baseType>
                    <jxb:javaType name="java.lang.Integer"
                        parseMethod="forum7182533.NumberFormatter.parseInt" printMethod="forum7182533.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 forum7182533 -b bindings.xml format.xsd

Adapter1

This will cause an XmlAdapter to be created that leverages your formatter:

package forum7182533;

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

public class Adapter1
    extends XmlAdapter<String, Integer>
{


    public Integer unmarshal(String value) {
        return (forum7182533.NumberFormatter.parseInt(value));
    }

    public String marshal(Integer value) {
        return (forum7182533.NumberFormatter.printInt(value));
    }

}

Root

The XmlAdapter will be referenced from your domain object using the @XmlJavaTypeAdapter annotation:

package forum7182533;

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 you run the following demo code:

package forum7182533;

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

You will get the desired output:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root>
    <number>0000004</number>
</root>