Ignore enclosing braces with JSON parser while serializing object in Java

Question

I have the following classes:

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
public class User {

    private String id;
    private List<Reference> references;
.....
}

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
public class Reference {

    @JacksonXmlProperty(isAttribute = true)
    private String ref;

    public Reference(final String ref) {
        this.ref = ref;
    }

    public Reference() { }

    public String getRef() {
        return ref;
    }

}

When serializing to XML the format is as expected, but when I try to serialize to JSON I get the following

"users" : [
  {
      "references" : [
      {
        "ref": "referenceID"
      }
    ]
  }
]

And I need it to be:

"users" : [
  {
      "references" : [
        "referenceID"
    ]
  }
]

the braces enclosing the reference list I need it to be ignored without the attribute name