"If a thread attempts to use the connection while another one is using it, it will wait until the other thread has finished its current operation. If the operation is a regular SQL statement, then the operation consists of sending the statement and retrieving any ResultSet (in full)."
Consider this test case: one thread calls executeQuery("SELECT ..."), and while that query is still executing, a second thread calls close() on the statement.
Given the documentation above, I would expect the regular SQL statement to complete, the statement then to be closed, and no exception thrown.
I'll attach a sample code for this scenario. With the current git driver, this fails at getMaxRows().
When you change Jdbc4Statement.createResultset() so it uses this.maxrows instead of getMaxRows() and hence skip checkClosed, then that test will pass. Patch also attached, although I have no idea whether this really is the right thing to do.
Still, I will also check my code. I think this happens when a user closes a view while the data inside is (re)loading, so I'll probably have the error handling discard that exception in this case instead of ringing the alarm bell...