How tell get matched response type in an exception mapper?

[Rice Yeh]

Hi,
  I write a ExceptionMapper to handle exception. In the ExceptionMapper, I
have a need to know the matched response type to return different response.
For example, if the the matched response type is html, it returns a html
response and if the matched response is  json, it returns json. How do I do
this?

Regards,
Rice