com.zaxxer.hikari.pool.ProxyConnection$ClosedConnection should return false for isClosed() instead of throwing an exception

[tomdcc]

Environment

HikariCP version: 3.1.0
JDK version     : 1.8.0_111
Database        : PostgreSQL
Driver version  : 42.1.4

See https://github.com/brettwooldridge/HikariCP/blob/HikariCP-3.1.0/src/main/java/com/zaxxer/hikari/pool/ProxyConnection.java#L478

It's not possible to check if a connection is closed by calling isClosed() without special exception handling as Hikari throws an exception. There should be a check for the isClosed method in the handler that should just return false.

[brettwooldridge]

@tomdcc Is that true? The implementation of isClosed() seems correct (and does not throw). We have a test that validates that the behavior is correct.

Are you possibly calling isClosed() on a Connection that you have unwrapped via unwrap() after closing the Connection?

[tomdcc]

Sorry for the delay in replying, I haven't had time to try to recreate it, and the code that was triggering this has changed somewhat so it's not straight forward.

I could have sworn that the reported stack trace showed the exception being thrown by ClosedConnection. That code was doing some unwrapping at one point, though.

Hmm. It does look like this sequence might do it, though I haven't verified it:

Connection con = proxyConnection.unwrap(Connection.class);
// ...
con.isClosed();

This is simplified, the code as it stands doesn't make much sense. The unwrapping was happening away from the isClosed() call.

Caller expects to get an unwrapped connection for some reason, but gets the ClosedConnection delegate instead. They then call isClosed() and sadness ensues.

[brettwooldridge]

We can certainly add isClosed() to the interceptor. While an unusual pattern, it still should not throw an exception.