ServletOutput.println violates Async Writer contract

[gregw]

The ServletOutput.println methods are implemented as follows:

    public void println(String s) throws IOException {
        print(s);
        println();
    }

This violates the API contract for asynchronous writers because isReady() needs to be called before every write/print. In this case the print(s) may fill a buffer, which is flushed and hits TCP/IP congestion. The output stream is now not ready, but the println() call is made regardless!

[joakime]

Couldn't the implementation be changed (or as a workaround, be overridden) to ...

    public void println(String s) throws IOException {
        print(s + System.lineSeparator());
    }

[gregw]

@joakime that would work, although it's not that efficient.... it would be better to add the line separator as the string is converted to a byte arrray.... oh wait there is another problem with print(String) as it does the string to byte conversion character by character, with write(byte) calls inbetween. This also violates the async write contract!

[stuartwdouglas]

I think having less efficient but technically correct implementations is an ok compromise, as implementors can always override to whatever is most efficient for their implementations.

[gregw]

Good point! I'll prepare a PR with some minimal correct implementations