RE: Atomic transaction in iBATIS

Jean-Francois Poilpret Mon, 06 Mar 2006 07:38:37 -0800

Hi Tony,

I don’t think transaction boundaries are the concerns of DAO.

Generally stated transaction is a “cross-cutting concern”.

If you use EJB or one lightweight container like Spring or HiveMind then transactions are supported _declaratively_ at any level (but preferrably you should put them at service level).

All the containers above are able to create a transaction if no one exists at call time, or reuse the current transaction if one is already open. And that happens without any transaction management code anywhere!

In any case (I mean: even if you don’t use containers, be it EJB or lightweight), it is never a good idea to hard-code the transaction boundaries at the DAO level, because your DAO has only one responsibility: access one piece of data of your DB independently of any transaction. Putting transactions there would be giving too much responsibility to it (and prevent higher level services to define wider transactions).

Transactions will most often embed many calls to several DAOs, and you have to put your transaction boundaris to where they belong (ie the services that call the DAO).

Cheers

Jean-Francois

From: Tony Qian [mailto:[EMAIL PROTECTED]
Sent: Monday, March 06, 2006 10:03 PM
To: [email protected]
Subject: Atomic transaction in iBATIS

All,

I need an atomic transaction for inserting data to several tables. iBATIS supports that. I looked at the jpetstore code. I found that atomic transaction could be made at both service and DAO level. Here are some jpetstore codes.

in OrderService.java
public void insertOrder(Order order) {
    try {
      // Get the next id within a separate transaction
      order.setOrderId(getNextId("ordernum"));

      daoManager.startTransaction();

      itemDao.updateAllQuantitiesFromOrder(order);
      orderDao.insertOrder(order);

      daoManager.commitTransaction();
    } finally {
      daoManager.endTransaction();
    }
}

in AccountSqlMapDao.java
public void insertAccount(Account account) {
    update("insertAccount", account);     // btw, why is update? should it be insert? it seems to me that actual action is controlled by action id not by key word (update)
    update("insertProfile", account);
    update("insertSignon", account);
}

in AccountService.java
public void insertAccount(Account account) {
    accountDao.insertAccount(account);
}

insertOrder is apparently an atomic transaction, which is enforced at service level. My question is whether insertAccount is an atomic transaction, i.e. what if "update("insertSignon", account);" fails? Should we enforce it at DAO level (put three updates between startTransaction and endTransaction)? or we can do same thing as inserOrder, i.e. put "accountDao.insertAccount(account);" between daoManager.startTransaction and daoManager.endTransaction.

If we use Abator to generate the DAO code, it makes sense that atomic transaction is enforced at service level. But from software architecture point of view, atomic transaction should be pushed down to DAO level. any suggestions?

thanks,
Tony

RE: Atomic transaction in iBATIS

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