Array null or empty in JSON on Jersey WS

Question

I have a WS implemented with Java Jersey (with Swagger). I need to receive in a parameter in json body, which is an array, a list with values, or a list without any values, or a null (baecause in each one of this cases i need a different behaviour) This is my json:

{
    "email": "[email protected]",
    "name": "SHELDON COOPER2",
    "groups": [17,25]
}

But i need to receive also these json: (With the list empty)

{
    "email": "[email protected]",
    "name": "SHELDON COOPER2",
    "groups": []
}

And with the list as null

{
    "email": "[email protected]",
    "name": "SHELDON COOPER2",
    "groups": null
}

Because for me is different, because if i receive the list without values i need to delete all the elements related with the user and if i receive the list as null i don't do antything.

The problem is with my implementation, the second and third case Java works in the same way (puts the parameter as null)

My code:

@PUT
@Path("/usuweb/{userId}")
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)

public Response actu_usuweb(@ApiParam(value = "Identificador del usuario web", required = true) @Size(max=32) @PathParam("userId") String userId
                                  ,@ApiParam(value = "Body", required = true) ActualizaUsuarioRequestV1 request) {
OracleConnection db = new OracleConnection();
ResponseDB response = new ResponseDB();


Gson gsonIn = new GsonBuilder().setPrettyPrinting().create();
JsonElement innerObject;
innerObject = gsonIn.toJsonTree(request);

innerObject.getAsJsonObject().addProperty("userId", userId); 

    
response = db.processRequest(getCurrentMethod().toUpperCase(), VERSION, innerObject.toString());
try
{
    return Response.status(response.getHttpCode()).entity(response.getJson()).build();
}
catch (Exception e) 
{
    ErrorResponse errorResponse = new ErrorResponse();
    
    Gson gson = new GsonBuilder().setPrettyPrinting().create();
    JsonElement jsonElement;
    
    errorResponse.setErrorCode(Response.Status.INTERNAL_SERVER_ERROR.getStatusCode());
    errorResponse.setErrorMessage("Ha ocurrido un error.");
    
    jsonElement = gson.toJsonTree(errorResponse);
    
    return Response.status(Response.Status.INTERNAL_SERVER_ERROR).entity(jsonElement.toString()).build();
}        

}

The java Structure:

package structuresV1;

import io.swagger.annotations.ApiModelProperty;

import javax.validation.constraints.Size;

public class ActualizaUsuarioRequestV1 {
    
    @ApiModelProperty(value = "") @Size(max=255)
    private String email;
    
    @ApiModelProperty(value = "") @Size(max=100)
    private String name;
          
    @ApiModelProperty(value = "") @Size(max=10)
    private String[] groups;
    

    public void setEmail(String email) {
        this.email = email;
    }

    public String getEmail() {
        return email;
    }

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

    public String getName() {
        return name;
    }

   
    public void setGroups(String[] groups) {
        this.groups = groups;
    }

    public String[] getGroups() {
        return groups;
    }
}

When i convert the request body in json with gson library, the parameter groups doesn't exist:

{
   "email":"[email protected]",
   "name":"SHELDON COOPER2",
   "userId":"dsad"
}

And in the database I can not differentiate in which case I am

Thanks & Regards.