CODEWITHSUNDEEP
xmljaxbmarshallingxmladapter
Edmond
Edmond

Reputation: 644

How to let JAXB exclude empty node?

I'm using JAXB to serialize objects to XML. Now I realize that it will exclude natural null values from response but will not exclude null values from customized adapters. Below is my code.

package com.model;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.adapters.XmlAdapter;

public class JAXBTest {

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

    Marshaller marshaller = jc.createMarshaller();
    marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

    Thing thing = new Thing();
    thing.setName("popcorn ball");

    thing.setAwesome(false);
    marshaller.setAdapter(BooleanAdapter.class,new BooleanAdapter(true));
    marshaller.marshal(thing, System.out);

}

@XmlRootElement 
public static class Thing{
    private String name;
    private Boolean awesome;
    private String empty;

    public String getEmpty() {
        return empty;
    }
    public void setEmpty(String empty) {
        this.empty = empty;
    }

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

    public void setAwesome(Boolean awesome) {
        this.awesome = awesome;
    }
    public Boolean isAwesome() {
        return this.awesome;
    }
}

public static class BooleanAdapter extends XmlAdapter<String, Boolean> {

    boolean flag;

    public BooleanAdapter(boolean flag){
        this.flag = flag;
    }

    public Boolean unmarshal(String v) throws Exception {
        return Boolean.TRUE.equals(v);
    }

    public String marshal(Boolean v) throws Exception {
        if(flag){
             if(v) {
                return v.toString();
            }
            return null;
        }else{
            return v.toString();
        }          
    }
}
}

packageinfo.java:

@XmlJavaTypeAdapter(value=JAXBTest.BooleanAdapter.class, type=Boolean.class)
package com.model;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

Output:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<thing>
    <awesome/>
    <name>popcorn ball</name>
</thing>

As you can see, even I return null in the Adapter, there is still an empty node in the response awesome/. The natural null field "private String empty" is perfectly ignored. So my question is, how to exclude these empty nodes from response?

Upvotes: 2

Views: 3033

Answers (1)

Ed Randall
Ed Randall

Reputation: 7600

For an element use an empty class rather than a String, only adapt TRUE to your class. (Maybe new Object() would work but I havn't tried that.)

public class BooleanXmlElement {

    public BooleanXmlElement() {
    }


    public static class Adapter extends XmlAdapter<BooleanXmlElement, Boolean> {

        public Boolean unmarshal(BooleanXmlElement v) {
            return Boolean.TRUE;
        }

        public BooleanXmlElement marshal(Boolean v) {
            if (Boolean.TRUE.equals(v)) {
                return new BooleanXmlElement();
            }
            return null;
        }
    }
}

This didn't work for attributes however, for them a String seems necessary:

public class BooleanXmlAttribute extends XmlAdapter<String, Boolean> {

    public Boolean unmarshal(String v) {
        return Boolean.valueOf(v);
    }

    public String marshal(Boolean v) {
        if (Boolean.TRUE.equals(v)) {
            return Boolean.TRUE.toString();
        }
        return null;
    }
}

To cover both Boolean and boolean annotate your package for both:

@XmlJavaTypeAdapters({
    @XmlJavaTypeAdapter(value=BooleanXmlElement.Adapter.class, type=boolean.class),
    @XmlJavaTypeAdapter(value=BooleanXmlElement.Adapter.class, type=Boolean.class)
})
package com.model;

Edit: delete the line:

marshaller.setAdapter(BooleanAdapter.class,new BooleanAdapter(true));

you don't need it.

Upvotes: 0

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