使用ajax将userPrincipal传递给HttpServletRequest

Question

我有一个接收POST请求的REST服务。 userPrincipal是必需参数，因为它在其他API中使用。无论如何，我似乎无法将其传递给HttpServletRequest对象。我怎样才能将userPrincipal值传递给他？我是否必须在标题，参数或其他地方添加它？两者似乎都不起作用。

REST服务代码：

@POST
@Path("{id}/dothings")
@Produces("application/json")
@Consumes("multipart/form-data")
public Response doThings(@Context HttpServletRequest request, @PathParam("id") String id, MultipartFormDataInput payload) {
        String username = request.getUserPrincipal() != null ? request.getUserPrincipal().getName() : null;
        //username is always null
        doSomething(username, payload);
}

Ajax调用代码：

var param = new FormData();
param.append('param1' , value1);
param.append('param2' , value2);
$.ajax({
    url: findUrl("dothings"),
    dataType : "application/json",
    contentType:false,
    processData:false,
    headers: {
        "Authorization" : authAdmin, //string containing "Basic "+ base64encoding(username+":"+password), for authentication
        "Accept" : "application/json"
    },
    type:"POST",
    data: param,
    success: function(data) {
        alert("executed!");
    },
    error : function(jqXHR, error, errorThrown) {
        alert("Error while completing task: " + errorThrown);
    }
});