How to skip the null fields during jaxb marshalling

Question

Is there a way for marshaller to generate a new xml file skipping any null attributes? So something like someAttribute="" does not show up in the file.

Thanks

Solution

A JAXB (JSR-222) implementation will not marshal a field/property annotated with @XmlAttribute that contains a null value.

Java Model (Root)

import javax.xml.bind.annotation.*;

@XmlRootElement
public class Root {

    private String foo;
    private String bar;

    @XmlAttribute
    public String getFoo() {
        return foo;
    }

    public void setFoo(String foo) {
        this.foo = foo;
    }

    @XmlAttribute(required=true)
    public String getBar() {
        return bar;
    }

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

}

Demo Code

import javax.xml.bind.*;

public class Demo {

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

        Root root = new Root();
        root.setFoo(null);
        root.setBar(null);

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

}

Output

<?xml version="1.0" encoding="UTF-8"?>
<root/>

Comments

[user2167013]

Thank you so much for your answer. However, I checked my jaxb version lnx-davidw:/export/home/davidw/JavaProj/xsd 1837=> xjc -version xjc version "JAXB 2.1.10" JavaTM Architecture for XML Binding(JAXB) Reference Implementation, (build JAXB 2.1.10) lnx-davidw:/export/home/davidw/JavaProj/xsd 1839=> /usr/bin/java -version java version "1.6.0_22" OpenJDK Runtime Environment (IcedTea6 1.10.4) (rhel-1.24.1.10.4.el5-x86_64) OpenJDK 64-Bit Server VM (build 20.0-b11, mixed mode) lnx-davidw:/export/home/davidw/JavaProj/xsd 1840=> /usr/bin/javac -version javac 1.6.0_22 I should have that, should I?

[bdoughan]

@user2167013 - The behaviour I described should be the same for all JAXB versions an implementations. Are you sure your value is null and not "".