Play! framework immediate save?

Question

In Play! if you call this:

void method()
{
User u = User();
u.name = \"bob\";
u.save();
while(true){/* endless loop */}
}

Nothing will actually

Answer 1

The reason why your changes are not visible in the database, is that the transaction is not yet commited and so other transactions can't see your changes (at least in a good database like PostgreSQL, Oracle, MSSQL, DB2). To make your changes seen, you'll have to commit your transaction before it enters the infinite loop, like this:

void method()
{
    User u = User();
    u.name = "bob";
    u.save();
    JPA.em().flush();
    JPA.em().getTransaction().commit();

    while(true){/* endless loop */}

}

If you want to access your database inside the infinite loop or after it (if you have a break condition), you'll have to begin a new transaction or you'll get exceptions from hibernate. Do this like this

void method()
{
    User u = User();
    u.name = "bob";
    u.save();
    JPA.em().flush();
    JPA.em().getTransaction().commit();

    while(true){
      // do some stuff

      /* TRANSACTIONAL BLOCK BEGINS */
      JPA.em().getTransaction().begin();
      try{
          // do some stuff
          // fetching, updating, deleting, whatever

          JPA.em().getTransaction().commit();
      }
      catch (Exception e)
      {
          // if an error occurs, rollback the transaction
          JPA.em().getTransaction().rollback();
      }
      /* TRANSACTIONAL BLOCK ENDS */
      // do some other stuff
    }
   // copy the TRANSACTIONAL BLOCK from above, if you want to do stuff after the "infinite loop" as well.
}

It's important that you either commit or rollback the transaction in the loop, if you start it there, as else you'll run into problems with too many open transactions soon.