@Override @POST @Path("/username/") public String devicesFromUsername(@FormParam("username") final String username) { List<Device> devices = findDevicesByUsername(username); String result = "{\"username\":\"" + username + "\",\"devices\":["; String sDevices = ""; Iterator<Device> i = devices.iterator(); while (i.hasNext()) { Device d = i.next(); sDevices += "\"" + d.getDeviceId() + "\","; } if (sDevices.length() > 0) { sDevices = sDevices.substring(0, sDevices.length() - 1); } result += sDevices + "]}"; return result; }