JdbcTemplate with TransactionTemplate

JdbcTemplate with TransactionTemplate

If you look at the code for JdbcTemplate (one of the execute(...) methods) you will see

Connection con = DataSourceUtils.getConnection(getDataSource());
Which tries to retrieve a Connection from a ConnectionHolder registered with a TransactionSynchronizationManager.

If there is no such object, it just gets a connection from the DataSource and registers it (if it is in a transactional environment, ie. you have a transaction manager). Otherwise, it immediately returns the registered object.

This is the code (stripped of logs and stuff)

ConnectionHolder conHolder = (ConnectionHolder) TransactionSynchronizationManager.getResource(dataSource);
if (conHolder != null && (conHolder.hasConnection() || conHolder.isSynchronizedWithTransaction())) {
    conHolder.requested();
    if (!conHolder.hasConnection()) {
        conHolder.setConnection(dataSource.getConnection());
    }
    return conHolder.getConnection();
}
// Else we either got no holder or an empty thread-bound holder here.

Connection con = dataSource.getConnection();

// flag set by the TransactionManager
if (TransactionSynchronizationManager.isSynchronizationActive()) {
    // Use same Connection for further JDBC actions within the transaction.
    // Thread-bound object will get removed by synchronization at transaction completion.
    ConnectionHolder holderToUse = conHolder;
    if (holderToUse == null) {
        holderToUse = new ConnectionHolder(con);
    }
    else {
        holderToUse.setConnection(con);
    }
    holderToUse.requested();
    TransactionSynchronizationManager.registerSynchronization(
                new ConnectionSynchronization(holderToUse, dataSource));
    holderToUse.setSynchronizedWithTransaction(true);
    if (holderToUse != conHolder) {
        TransactionSynchronizationManager.bindResource(dataSource, holderToUse);
    }
}

return con;
You'll notice that the JdbcTemplate tries to

finally {
    DataSourceUtils.releaseConnection(con, getDataSource());
}
release the Connection, but this only happens if you're in a non-transactional environment, ie.

if it is not managed externally (that is, not bound to the thread).
Therefore, in a transactional world, the JdbcTemplate will be reusing the same Connection object.