I am not familiar with jsp  but just looking at the code  I can see one
possible problem. The out.flush() is probably causing your error. I took
this from the PrintStream class definition:

Optionally, a PrintStream can be created so as to flush automatically; this
means that the flush method is automatically invoked after a byte array is
written, one of the println methods is invoked, or a newline character or
byte ('\n') is written.