关于UserTransaction

 

public class UserTransaction {
    private static Map threadDbconnectionMap = new HashMap();
    public void begin() {
        dataSource.getConnection().setAutoCommit(false);
        threadDbConnectionMap.put(Thread.currentThread(), dataSource.getConnection());    
        dataSource.getConnection().startTransaction();
    }

    public void commit() {
        dataSource.getConnection().commitTransaction();
        threadDbConnectionMap.remove(Thread.currentThread());        
    }
}

public class DataSource {
    private static Map threadDbConnectionMap = new HashMap();    
    public Connection getConnection() {
       if(threadDbConnectionMap.get(Thread.currentThread()) == null) {
          threadDbConnectionMap.put(Thread.currentThread(), DBCONNECTION_POOL.getConnection);
       }
          return (Connection)threadDbConnectionMap.get(      Thread.currentThread());
    }
}

UserTransaction的机制就是建立一个currentThread和一个DBconnection的map，使得在同一个thread下的所有db operation使用同一个connection，这样通过背后的同一个connection的commit或rollback来保证transaction的atomic