How to map a bean property to an XML attribute in JAXB?

In this example you will learn how to define a bean / pojo property as an XML attribute in JAXB. To define properties as an XML attribute we use the @XmlAttribute annotation. In the Student class below the id property will defined as an attribute of the student root element. While the name and grade property will be an element of the student.

package org.kodejava.example.jaxb;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Student {
    private Integer id;
    private String name;
    private Integer grade;

    @XmlAttribute
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public Integer getGrade() {
        return grade;
    }

    public void setGrade(Integer grade) {
        this.grade = grade;
    }
}

Here the program that we can use to convert the Student bean into an XML document.

package org.kodejava.example.jaxb;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import java.io.FileWriter;
import java.io.IOException;

public class JAXBElementAttribute {
    public static void main(String[] args) {
        Student student = new Student();
        student.setId(1);
        student.setName("Alice");
        student.setGrade(12);

        try {
            JAXBContext context = JAXBContext.newInstance(Student.class);
            Marshaller marshaller = context.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
            marshaller.marshal(student, new FileWriter("Student.xml"));
        } catch (JAXBException | IOException e) {
            e.printStackTrace();
        }
    }
}

When you run the program a file named Student.xml will be created with the following content:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<student id="1">
    <grade>12</grade>
    <name>Alice</name>
</student>

How to generate a wrapper element around XML representation in JAXB?

In this example you’ll learn how to use the JAXB @XmlElementWrapper annotation. This annotation can be use to generate a wrapper element around an XML element representation. When no name defined, the @XmlElementWrapper annotation uses the property name as the wrapper element name. Let’s see the code snippet below.

package org.kodejava.example.jaxb;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;
import java.util.ArrayList;
import java.util.List;

@XmlRootElement
public class Record {
    private Integer id;
    private String title;
    private List<Track> tracks = new ArrayList<>();

    @XmlRootElement
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    @XmlElementWrapper(name = "trackList")
    @XmlElement(name = "track")
    public List<Track> getTracks() {
        return tracks;
    }

    public void setTracks(List<Track> tracks) {
        this.tracks = tracks;
    }
}

Below is the code snippet for marshaling the Record object into an XML document. Before the marshalling take place we create an object of Record and adds a some Track into it.

package org.kodejava.example.jaxb;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;

public class JAXBElementWrapper {
    public static void main(String[] args) {
        Track track1 = new Track();
        track1.setId(1);
        track1.setTitle("Love Me Do");

        Track track2 = new Track();
        track2.setId(2);
        track2.setTitle("From Me To You");

        Track track3 = new Track();
        track3.setId(3);
        track3.setTitle("She Loves You");

        Record record = new Record();
        record.setId(1);
        record.setTitle("The Beatles 1");
        record.getTracks().add(track1);
        record.getTracks().add(track2);
        record.getTracks().add(track3);

        try {
            JAXBContext context = JAXBContext.newInstance(Record.class);
            Marshaller marshaller = context.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
            marshaller.marshal(record, System.out);

            Writer writer = null;
            try {
                writer = new FileWriter("Record.xml");
                marshaller.marshal(record, writer);
            } finally {
                if (writer != null) {
                    writer.close();
                }
            }
        } catch (JAXBException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

The above program will generated the following XML document.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<record id="1">
    <title>The Beatles 1</title>
    <trackList>
        <track id="1">
            <title>Love Me Do</title>
        </track>
        <track id="2">
            <title>From Me To You</title>
        </track>
        <track id="3">
            <title>She Loves You</title>
        </track>
    </trackList>
</record>

How to convert object to XML using JAXB?

JAXB, Java Architecture for XML Binding, it uses JAXB annotations to convert POJO to or from XML file. In this example you will learn how to convert an object / POJO into an XML document using JAXB. The process of converting an object into XML also known as marshalling. JAXB is part of the JDK since 1.6 so you don’t need other library when using JAXB. In this snippet our POJO is a class called Track as you can see below.

The first thing that we need to do is to annotate the Track POJO with a couple of JAXB annotations. For this example we add the @XmlRootElement, @XmlElement and @XmlAttribute annotations.

package org.kodejava.example.jaxb;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Track {
    private Integer id;
    private String title;

    public Track() {
    }

    public Integer getId() {
        return id;
    }

    @XmlAttribute
    public void setId(Integer id) {
        this.id = id;
    }

    @XmlElement
    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    @Override
    public String toString() {
        return "Track{" +
                "id=" + id +
                ", title='" + title + ''' +
                '}';
    }
}

After we have the Track class annotated we can use the code snippet below to convert the POJO into XML. The steps to do it start by creating an instance of JAXBContext. From this context object we create the Marshaller object. To convert it to XML we called the marshall() method. The method have many overloads, in this case we just want to print the XML to the System.out.

package org.kodejava.example.jaxb;

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

public class JAXBObjectToXml {
    public static void main(String[] args) {
        Track track = new Track();
        track.setId(1);
        track.setTitle("Hey Jude");

        try {
            JAXBContext context = JAXBContext.newInstance(Track.class);

            Marshaller marshaller = context.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
            marshaller.marshal(track, System.out);
        } catch (JAXBException e) {
            e.printStackTrace();
        }
    }
}

If you run this code you will get the following output:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<track id="1">
    <title>Hey Jude</title>
</track>

How to create an XML file of a POJO using JAXB?

The code snippet below show you how to convert POJO into XML file using JAXB. To do this we can pass the output file where we want the XML to be saved to the marshaller object.

package org.kodejava.example.jaxb;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import java.io.File;

public class JAXBObjectToXmlFile {
    public static void main(String[] args) {
        Track track = new Track();
        track.setId(2);
        track.setTitle("She Loves You");

        try {
            JAXBContext context = JAXBContext.newInstance(Track.class);

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

            File output = new File("Track.xml");
            marshaller.marshal(track, output);
        } catch (JAXBException e) {
            e.printStackTrace();
        }
    }
}

This snippet will create a file called Track.xml with the following content:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<track id="2">
    <title>She Loves You</title>
</track>

How to convert an XML file into object using JAXB?

In this code snippet you can learn how to convert or unmarshal an XML file into it corresponding POJO. The steps on unmarshalling XML to object begin by creating an instance of JAXBContext. With the context object we can then create an instance of Unmarshaller class. Using the unmarshall() method and pass an XML file will give us the target POJO as the result.

Let’s see the code snippet below:

package org.kodejava.example.jaxb;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;
import java.io.File;

public class JAXBXmlToObject {
    public static void main(String[] args) {
        try {
            File file = new File("Track.xml");
            JAXBContext context = JAXBContext.newInstance(Track.class);

            Unmarshaller unmarshaller = context.createUnmarshaller();
            Track track = (Track) unmarshaller.unmarshal(file);

            System.out.println("Track = " + track);
        } catch (JAXBException e) {
            e.printStackTrace();
        }
    }
}

Here is the context of Track.xml:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<track id="2">
    <title>She Loves You</title>
</track>

How do I define the XML element order in JAXB?

In this code snippet you will learn how to define the order of XML element generated by the JAXB API. To define the element order we need to use the @XmlType annotation in our POJO. This annotation propOrder is where we define what element should come first and which element should be place at the end.

The XML generated by the marshaller below will have the following order: street, city, province, zipCode and country as the last XML element.

package org.kodejava.example.jaxb;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlRootElement(name = "customerAddress")
@XmlType(propOrder = {"street", "city", "province", "zipCode", "country"})
public class Address {
    private String street;
    private String city;
    private String province;
    private String country;
    private String zipCode;

    @XmlElement
    public String getStreet() {
        return street;
    }

    public void setStreet(String street) {
        this.street = street;
    }

    @XmlElement
    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    @XmlElement
    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
    }

    @XmlElement
    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    @XmlElement(name = "postCode")
    public String getZipCode() {
        return zipCode;
    }

    public void setZipCode(String zipCode) {
        this.zipCode = zipCode;
    }

    @Override
    public String toString() {
        return "Address{" +
                "street='" + street + ''' +
                ", city='" + city + ''' +
                ", province='" + province + ''' +
                ", country='" + country + ''' +
                ", zipCode='" + zipCode + ''' +
                '}';
    }
}

Now, let’s create a program to run the marshalling process of the Address POJO to convert it into XML document:

package org.kodejava.example.jaxb;

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

public class JAXBElementOrder {
    public static void main(String[] args) {
        Address address = new Address();
        address.setStreet("Sunset Road");
        address.setCity("Denpasar");
        address.setProvince("Bali");
        address.setCountry("Indonesia");
        address.setZipCode("800000");

        try {
            JAXBContext context = JAXBContext.newInstance(Address.class);

            Marshaller marshaller = context.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
            marshaller.marshal(address, System.out);
        } catch (JAXBException e) {
            e.printStackTrace();
        }
    }
}

And it will give you the following output:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<customerAddress>
    <street>Sunset Road</street>
    <city>Denpasar</city>
    <province>Bali</province>
    <country>Indonesia</country>
    <postCode>800000</postCode>
</customerAddress>

How do I change the XML root element name in JAXB?

In the following code snippet you will learn how to change the default root element name of the XML generated by the JAXB API. By default the name of the class is use as the root element name. To change the root element name we can use the name property of the @XmlRootElement annotation. In the Customer model below we change the root element name into cust.

package org.kodejava.example.jaxb;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlRootElement(name = "cust")
@XmlType(propOrder = {"id", "name", "address"})
public class Customer {
    private Integer id;
    private String name;
    private Address address;

    @XmlElement
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    @XmlElement
    public String getName() {
        return name;
    }

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

    @XmlElement
    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }
}

When we convert this POJO to XML using JAXB API we will get the following result:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<cust>
    <id>1</id>
    <name>Johnny Mnemonic</name>
    <address>
        <street>Sunset Road</street>
        <city>Denpasar</city>
        <province>Bali</province>
        <postCode>800000</postCode>
        <country>Indonesia</country>
    </address>
</cust>