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Chris,
On 10/11/17 5:21 PM, Chris Cheshire wrote:
> Working on a migration from 7 to 8.5, and in it I am now using the
> tomcat dbcp, instead of apache commons dbcp.> I have found that
> with no other changes to the db code (except the factory param for
> the resource), it is working fine other than there is an implicit
> commit happening when I close a connection, even with autocommit
> turned off in mysql config, resource config AND in my code.
Your complaint is very close to my heart, here. <3
Back in 2003 or so, I posted roughly this exact question to this
mailing list with a little less ... diplomacy, shall we say?
> try { this.dbConn = this.dataSource.getConnection();
> this.dbConn.setAutoCommit(false);
> this.dbConn.setTransactionIsolation(Connection.TRANSACTION_READ_COMMIT
TED);
>
>
}
> catch (SQLException ex) { throw new DAOException("unable to get
> database connection", ex); }
I'll bet you've had this problem for a really long time, but just
didn't notice it until now.
The core problem is that you have autocommit=false in your
configuration and autocommit=true in your code. If an exception occurs
and you don't rollback the transaction, the connection pool will reset
all of the settings to your configured settings (including
autocommit=true). Setting autocommit=true when autocommit=false
commits the transaction, which is SUPER surprising to anyone who
hasn't read the Javadoc[1]
Technically, this happens whether you encounter an exception or not,
but it's fairly rare to have code that intentionally does this:
conn.setAutoCommit(false);
// UPDATE ...;
conn.close();
So, given that this is usually an "exceptional" situation, it's your
exceptions you need to carefully handle. In fact, you need to do more
than you are used to doing.
Have a look at this post I did years later when related questions kept
coming up on the list:
http://blog.christopherschultz.net/index.php/2009/03/16/properly-handlin
g-pooled-jdbc-connections/
Hope that helps,
- -chris
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