JAXB @XmlElementWrapper Annotation Example

Java example of JAXB @XmlElementWrapper annotation in detail along with its usage during marshalling and unmarshalling operations.

1) @XmlElementWrapper Type

1. This annotation generates a wrapper element around XML representation.
2. This is primarily intended to be used to produce a wrapper XML element around collections.
3. This annotation can be used with the following annotations: XmlElement, XmlElements, XmlElementRef, XmlElementRefs, XmlJavaTypeAdapter.
4. The @XmlElementWrapper annotation can be used with the following program elements:
   • JavaBean property
   • non static, non transient field

2) @XmlElementWrapper Example

Now see few examples of how using @XmlElementWrapper along with @XmlElement changes the XML representations.

2.1) Use @XmlElementWrapper and @XmlElement (Wrapped collection)

@XmlRootElement(name = "employee")
@XmlAccessorType(XmlAccessType.FIELD)
public class Employee implements Serializable {

	private static final long serialVersionUID = 1L;

	@XmlElementWrapper(name="hobbies")
	@XmlElement(name="hobby")
	private List<String> hobbies;

	private Integer id;
	private String firstName;
	private String lastName;
}

Above converts to:

<employee>
    <id>1</id>
    <firstName>Lokesh</firstName>
    <lastName>Gupta</lastName>

    <hobbies>
        <hobby>Swimming</hobby>
        <hobby>Playing</hobby>
        <hobby>Karate</hobby>
    </hobbies>

</employee>

2.2) Use Only @XmlElementWrapper

@XmlRootElement(name = "employee")
@XmlAccessorType(XmlAccessType.FIELD)
public class Employee implements Serializable {

	private static final long serialVersionUID = 1L;

	@XmlElementWrapper(name="hobbies")
	//@XmlElement(name="hobby")	//Comment it out
	private List<String> hobbies;

	private Integer id;
	private String firstName;
	private String lastName;
}

Above converts to:

<employee>
    <id>1</id>
    <firstName>Lokesh</firstName>
    <lastName>Gupta</lastName>

    <hobbies>
        <hobbies>Swimming</hobbies>
        <hobbies>Playing</hobbies>
        <hobbies>Karate</hobbies>
    </hobbies>

</employee>

2.3) Do not use @XmlElementWrapper (Unwrapped collection)

@XmlRootElement(name = "employee")
@XmlAccessorType(XmlAccessType.FIELD)
public class Employee implements Serializable {

	private static final long serialVersionUID = 1L;

	//@XmlElementWrapper(name="hobbies")	//Comment it out
	@XmlElement(name="hobby")			
	private List<String> hobbies;

	private Integer id;
	private String firstName;
	private String lastName;
}

Above converts to:

<employee>
    <id>1</id>
    <firstName>Lokesh</firstName>
    <lastName>Gupta</lastName>

    <hobby>Swimming</hobby>
    <hobby>Playing</hobby>
    <hobby>Karate</hobby>

</employee>>

Drop me your questions in comments section.

Happy Learning !!

Reference : XmlElementWrapper Java Doc