What is causing 'canceling statement due to user request' ?

Hi all,

I know of 2 causes:

 - hit CTRL-C in the psql client;
 - have a non-zero statement timeout and have the statement actually
time out;

But I am seeing this via JDBC which can't cancel a statement AFAIK, and
the statement_timeout is set to 0 (in the config file globally, and
there's no override for the users, nor in our JDBC code).

I wonder if there is any other scenario which can trigger this error ? I
found a lot of them in our logs, last night we had hundreds of them, but
now that I looked it happened sporadically in the past too...

Could some network problem trigger this ?

TIA,
Csaba.