Question

Jersey appears to have a set of predetermined default values for JSON nulls while unmarshalling via JAXB: String => “”, Integer => 0, … is there anyway to easily control these values either with configuration or annotations?

Using Jersey’s POJO mapping I get what I want, which is to map JSON null to Java null, but for other reasons we really need to use JAXB.

It seems like this should be simple however I’m drawing a blank.

Thanks.

Answer 1

Note: I’m the EclipseLink JAXB (MOXy) lead and a member of the JAXB (JSR-222) expert group.

The JAXB (JSR-222) specification does not cover JSON-binding so what you are experiencing is Jersey code interacting with the JAXB reference implementation producing some odd results wrt null handling. EclipseLink MOXy is a JAXB compliant implementation that also offers JSON binding that has more natural null handling.

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {

    private String firstName;

    @XmlElement(nillable=true) 
    private String lastName;

}

If this was marshalled to JSON the result would be the following. Null values are not marshalled to JSON unless they are annotated with @XmlElement(nillable=true):

{
    lastName: null
}

For More Information

• http://blog.bdoughan.com/2012/04/binding-to-json-xml-handling-null.html

Jersey Integration

• http://blog.bdoughan.com/2012/05/moxy-as-your-jax-rs-json-provider.html
• https://github.com/jersey/jersey/tree/master/examples/json-moxy