jmf中获取mp3设备？？？

private String url = "file:E:/music/感恩的心.mp3";
private CaptureDeviceInfo infor = null;
private MediaLocator mediaLocator = null;


infor = CaptureDeviceManager.getDevice(url);//定位所需要用的捕获设备
mediaLocator = infor.getLocator();


调试发现infor实例化是是null,想问一下，这样获取mp3文件对不对？？？
CaptureDeviceManager.getDevice()是不是只能获取视频和麦克风的设备？？？
谢谢！！！