JdbcDataSource synchronization

[Mark Miller]

JdbcDataSource looks like it has a little funkiness going on. Why is 
there a synchronize block there? Can multiple threads call getConnection 
concurrently? If they can, this is not thread safe anyway. If they 
can't, why is factory.call (or is it the close?) being protected with a 
sync?

private Connection getConnection() throws Exception {
   long currTime = System.currentTimeMillis();
   if (currTime - connLastUsed > CONN_TIME_OUT) {
     synchronized (this) {
       Connection tmpConn = factory.call();
       close();
       connLastUsed = System.currentTimeMillis();
       return conn = tmpConn;
     }
   } else {
     connLastUsed = currTime;
     return conn;
   }
 }