title: Spring @Transactional and JDBC autoCommit
body: <p>On my actual application, I have a DBCP connection pool which doesn't have JDBC autoCommit=false set. It seems to have the default autoCommit=true.
  This is probably a mistake but I'd like to understand the impact of changing this parameter.</p>
  
  <p>I am using:
   - Spring with @Transactional annotation
   - Spring Batch with JDBC readers and writers, eventually custom tasklets using JdbcTemplate</p>
  
  <p>I would like to know if Spring does set autoCommit=false on the current connection if it is in the context of a transaction handled by the TransactionManager.
  Does it override the default setting? Because it seems to me it makes sense to do so.</p>