Character encoding of ServletOutputStream print methods

The async API is only available on the output stream. Thus we have had a framework that used to do:

response.setContentType("application/json;charset=UTF-8");
...
response.getWriter().print("Ӝ");

convert to asynchronous style and now it does:

response.setContentType("application/json;charset=UTF-8");
...
response.getOutputStream().print("Ӝ");

This works fine on some containers (eg Jetty), but apparently many containers do not respect the encoding set by the setContentType. They either convert the character as ISO8859-1 or if the first character is UTF-8, they throw a CharacterEncoding exception.

We have also seen at least one container handle the following writes out of order:

response.getOutputStream().print("one");
response.getOutputStream().write("two".getBytes(UTF_8);
response.getOutputStream().print("three");

As the async API will now make more character oriented frameworks use the output stream, I believe that we need to clarify the semantics of the ServletOutputStream print method so that it:

+ is definitely mix and match with write - so we must say that print cannot buffer any data.
+ respects the character encoding set on the response