Java Connection Pool and try-with statements: Is Connection actually closed or returned to pool?

Question

I have a jdbc connection pool using the KeyedObjectPool class and i use it via the implemented methods openConnection() and closeConnection(). closeConnection() normally just returns the connection to the pool and closes it only if it has been used to often before. Therefore it uses ConnectionPool.returnObject() which does NOT close the connection object (see here).

class ConnectionPool
{

public openConnection(...)
{
   ...
}

public closeConnection()
{
   ...
}
}

However, if i use the connection pool like this:

    try (Connection connection = sConnectionPool.openConnection(JdbcCredentials);)
    {
        doSomething();
    }
    catch (Exception e) 
    {
       ...
    }

Is the connection object using try-with only returned to the pool or actually closed with connection.close() (which i don't want to happen because it would make my pool useless)?

score 0 · Answer 1 · answered Sep 15 '17 at 10:23

0

It's actually a wrapper around the actual connection. It will, under the covers, release the actual connection back to the pool. It's further up to the pool to decide whether the actual connection will actually be closed or be reused for a new getConnection().

answered Sep 15 '17 at 10:23

saurabh2208

72
1
1
7

I tried out my application and it does not seem to work. How does the JVM know that my connection is taken from a connection pool, and that it should use `closeConnection()` instead of `connection.close()`? – flixe Sep 20 '17 at 09:27

user207421 · Answer 2 · 2017-09-15T10:00:10.203

-1

close() on a pooled connection returns it to the pool, regardless of whether that was caused by the try or your own code.

Otherwise it wouldn't be reusable, so it wouldn't be a connection pool.

edited Sep 15 '17 at 10:00

answered Sep 15 '17 at 09:53

user207421

305,947
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@downvoter Pray tell. A closed connection *is* reusable? How? – user207421 Sep 15 '17 at 09:59
You've misunderstood the question. This isn't an answer. – teppic Sep 15 '17 at 10:02
@teppic The `try` causes a `close()`, and the `close()` returns it to the pool, which is what the OP is asking about. – user207421 Sep 15 '17 at 10:03
@teppic OP has now accepted an answer saying exactly the same thing. – user207421 Sep 16 '17 at 23:44

Java Connection Pool and try-with statements: Is Connection actually closed or returned to pool?

2 Answers2