By default all properties of an instance are marshalled as elements in an xml file. As shown below..

Marshalling an Country insance with below class structure

Country

package package2;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Country {
    private int id;
    private String name;
    private int population;

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getPopulation() {
        return population;
    }
    public void setPopulation(int population) {
        this.population = population;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("{");
        sb.append("name:").append(this.name).append(",");
        sb.append("population:").append(this.population).append("}");

        return sb.toString();
    }
}

will result in below xml
<?xml version=”1.0″ encoding=”UTF-8″ standalone=”yes”?>
<country>
<id>1</id>
<name>India</name>
<population>10000000</population>
</country>

If we don’t want population attribute from being marshalled, we can achieve that by marking the “getPopulation” getter with annotation @XmlTransient as shown below

@XmlTransient
public int getPopulation() {
    return population;
}

will result in below xml
<?xml version=”1.0″ encoding=”UTF-8″ standalone=”yes”?>
<country>
<id>1</id>
<name>India</name>
</country>

Main Code

package package2;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;

public class XMLTransientDemo {
    public static void main(String[] args) throws JAXBException, IOException {
        JAXBContext jaxbContext = JAXBContext.newInstance(Country.class);

        Marshaller marshaller = jaxbContext.createMarshaller();
        Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();

        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

        File file = new File("result.xml");
        FileWriter fw = new FileWriter(file);

        Country country = new Country();
        country.setId(1);
        country.setName("India");
        country.setPopulation(10000000);
        
        marshaller.marshal(country, fw);
    }
}