@XmlElementWrapper Annotation for XML – JAXB

HOME

The previous tutorials explain how to use JAXB(Java Architecture for XML Binding) to parse XML documents to Java objects and vice versa. This is also called Marshalling and Unmarshalling.

This tutorial explains @XmlElementWrapper Annotation.

Configure the Java compiler level to be at least 11 and add the JAXB dependencies to the pom file.

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

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.example</groupId>
  <artifactId>JAXBDemo</artifactId>
  <version>0.0.1-SNAPSHOT</version>

  <name>JAXBDemo</name>
  <url>http://www.example.com</url>

  <properties>  

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>11</maven.compiler.source>
    <maven.compiler.target>11</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13.2</version>
      <scope>test</scope>
  </dependency>
    
 <dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-impl</artifactId>
    <version>2.3.3</version>
   </dependency>
 </dependencies>
   
</project>

@XmlElementWrapper generates a wrapper element around XML representation. This is primarily intended to be used to produce a wrapper XML element around collections.

This annotation can be used with the following annotations –  XmlElementXmlElementsXmlElementRefXmlElementRefsXmlJavaTypeAdapter.

@XmlElementWrapper and @XmlElement (Wrapped collection)

Let us understand this with the help of an example shown below.

@XmlRootElement(name = "CustomerDetails")
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {

	private int id;

	private String name;
	private int yearOfBirth;
	private String emailId;
	private String streetAddress;

	private String postcode;

	@XmlElementWrapper(name = "emergencyContacts")
	@XmlElement(name = "Contact")
	private List<String> emergencyContacts;

	public Customer() {
		super();
	}

	public Customer(int id, String name, int yearOfBirth, String emailId, String streetAddress, String postcode,
			List<String> emergencyContacts) {
		super();
		this.id = id;
		this.name = name;
		this.yearOfBirth = yearOfBirth;
		this.emailId = emailId;
		this.streetAddress = streetAddress;
		this.postcode = postcode;
		this.emergencyContacts = emergencyContacts;
	}

	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 getYearOfBirth() {
		return yearOfBirth;
	}

	public void setYearOfBirth(int yearOfBirth) {
		this.yearOfBirth = yearOfBirth;
	}

	public String getEmailId() {
		return emailId;
	}

	public void setEmailId(String emailId) {
		this.emailId = emailId;
	}

	public String getStreetAddress() {
		return streetAddress;
	}

	public void setStreetAddress(String streetAddress) {
		this.streetAddress = streetAddress;
	}

	public String getPostcode() {
		return postcode;
	}

	public void setPostcode(String postcode) {
		this.postcode = postcode;
	}

	public List<String> getEmergencyContacts() {
		return emergencyContacts;
	}

	public void setEmergencyContacts(List<String> emergencyContacts) {
		this.emergencyContacts = emergencyContacts;
	}
}

Now, let us create a Test to convert these Java Objects to XML.

   @Test
	public void Test() {

		try {

			Customer cust = new Customer();
			cust.setId(1111);
			cust.setName("Tim");
			cust.setYearOfBirth(1988);
			cust.setEmailId("Test@test.com");
			cust.setStreetAddress("6, JaySmith, Dublin");
			cust.setPostcode("A12 YP22");

			cust.setEmergencyContacts(Arrays.asList("98675 12312", "88881 23415", "44123 67453"));

			// Create JAXB Context
			JAXBContext context = JAXBContext.newInstance(Customer.class);

			// Create Marshaller
			Marshaller jaxbMarshaller = context.createMarshaller();

			// Required formatting
			jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);

			// Write XML to StringWriter
			StringWriter sw = new StringWriter();
			jaxbMarshaller.marshal(cust, sw);

			// Print XML Content
			String xmlContent = sw.toString();
			System.out.println(xmlContent);

		} catch (PropertyException e) {
			e.printStackTrace();

		} catch (JAXBException e) {

		}
	}

Here, contact is within emergencyContacts, because contact is @XmlElement.

Use Only @XmlElementWrapper

@XmlRootElement(name = "CustomerDetails")
@XmlAccessorType(XmlAccessType.FIELD)

public class Customer {

	private int id;

	private String name;
	private int yearOfBirth;
	private String emailId;
	private String streetAddress;

	private String postcode;

	@XmlElementWrapper(name = "emergencyContacts")
 //	@XmlElement(name = "Contact") //Commented this
	private List<String> emergencyContacts;

	public Customer() {
		super();
	}

	public Customer(int id, String name, int yearOfBirth, String emailId, String streetAddress, String postcode,
			List<String> emergencyContacts) {
		super();
		this.id = id;
		this.name = name;
		this.yearOfBirth = yearOfBirth;
		this.emailId = emailId;
		this.streetAddress = streetAddress;
		this.postcode = postcode;
		this.emergencyContacts = emergencyContacts;
	}

Here, there is no contact within emergencyContacts, it is because there is no @XmlElement for contact.

Do not use @XmlElementWrapper (Unwrapped collection)

@XmlRootElement(name = "CustomerDetails")
@XmlAccessorType(XmlAccessType.FIELD)

public class Customer {

	private int id;

	private String name;
	private int yearOfBirth;
	private String emailId;
	private String streetAddress;

	private String postcode;

 //@XmlElementWrapper(name = "emergencyContacts") Commented this
	@XmlElement(name = "Contact")
	private List<String> emergencyContacts;

	public Customer() {
		super();
	}

	public Customer(int id, String name, int yearOfBirth, String emailId, String streetAddress, String postcode,
			List<String> emergencyContacts) {
		super();
		this.id = id;
		this.name = name;
		this.yearOfBirth = yearOfBirth;
		this.emailId = emailId;
		this.streetAddress = streetAddress;
		this.postcode = postcode;
		this.emergencyContacts = emergencyContacts;
	}

Here, there is no @XmlElementWrapper. So, all the contact appear as attributes of XML.

I hope this has helped to understand the usage of @XmlElementWrapper.

We are done! Congratulations on making it through this tutorial and hope you found it useful! Happy Learning!!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s