截取@RequestHeader异常以获取缺少的标头

您应该使用@ExceptionHandler方法，该方法查看是否存在ETag标头并采取适当的措施：

@ExceptionHandler(UnsatisfiedServletRequestParameterException.class)public onErr400(@RequestHeader(value="ETag", required=false) String ETag,        UnsatisfiedServletRequestParameterException ex) {    if(ETag == null) {        // Ok the problem was ETag Header : give your informational message    } else {        // It is another error 400  : simply say request is incorrect or use ex    }}