Change ContentType or CharacterEncoding in Java Filter ONLY IF ContentType === JSON

Question

I\'m trying to ensure that all JSON responses from a Jersey based java application have a UTF-8 character encoding parameter appended to their ContentType header.

So

Answer 1

This is not going to work in this way.

When you call chain.doFilter(request, response); your headers are already flushed and you can't reset them later on.

What you can do is actually a quick and dirty trick:

public void doFilter(...) {
    HttpServletResponse resp = new HttpServletResponseWrapper(response) {
    public void setContentType(String ct) {
        if(ct!=null && ct.toLowerCase().startsWith("application/json")) {
            super.setContentType("application/json;charset=UTF-8");
        } else {
            super.setContentType(ct);
        }
   }
}

// Set content type manually to override any potential defaults,
// See if you need it at all
response.setContentType("application/json;charset=UTF-8");

chain.doFilter(request, resp); // Inject our response!
}

EDIT: ct.toUpperCase().startsWith("application/json") changed to ct.toLowerCase().startsWith("application/json").