Question

I have a class, that is something like this:

public class Property {

    private double floorArea;

    public double getFloorArea() {
        return floorArea;
    }

    @XmlElement
    public void setFloorArea(double floorArea) {
        this.floorArea = floorArea;
    }

}

Which will give me something like this:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<property>
    <floorArea>x</floorArea>
</property>

But I need something like this:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<property>
    <floorArea>
        <value>x</value>
    </floorArea>
</property>

The API I am using requires it this way. My limited JAXB knowledge is preventing me from figuring this out. Any help is appreciated.

EDIT:

something I am researching. Would I need to create a value class with its own JAXB annotations for this to work? (and set floorArea to the type of value)?

Answer 1

Below is how your use case could be supported with an XmlAdapter using any JAXB (JSR-222) implementation.

XmlAdapter (DoubleValueAdapter)

An XmlAdapter is a mechanism that allows an object to be converted to another type of object . Then it is the converted object that is converted to/from XML.

package forum14045961;

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

public class DoubleValueAdapter extends XmlAdapter<DoubleValueAdapter.AdaptedDoubleValue, Double>{

    public static class AdaptedDoubleValue {
        public double value;
    }

    @Override
    public AdaptedDoubleValue marshal(Double value) throws Exception {
        AdaptedDoubleValue adaptedDoubleValue = new AdaptedDoubleValue();
        adaptedDoubleValue.value = value;
        return adaptedDoubleValue;
    }

    @Override
    public Double unmarshal(AdaptedDoubleValue adaptedDoubleValue) throws Exception {
        return adaptedDoubleValue.value;
    }

}

Property

The @XmlJavaTypeAdapter annotation is used to specify the XmlAdapter. I needed to change double to Double so I moved the mapping to the field as to not affect the public API.

package forum14045961;

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

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Property {

    @XmlJavaTypeAdapter(DoubleValueAdapter.class)
    private Double floorArea;

    public double getFloorArea() {
        return floorArea;
    }

    public void setFloorArea(double floorArea) {
        this.floorArea = floorArea;
    }

}

Demo

Below is some demo code to prove that everything works.

package forum14045961;

import java.io.File;
import javax.xml.bind.*;

public class Demo {

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

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("src/forum14045961/input.xml");
        Property property = (Property) unmarshaller.unmarshal(xml);

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

}

input.xml/Output

Below is the input to and output from the demo code.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<property>
    <floorArea>
        <value>1.23</value>
    </floorArea>
</property>