AM.method() issues select for update (immediately) ??

Question

We have a thin client with BC4J optimistic locking and our own change indication logic
we're happy with.
We now need to implement a safe-region through a use case to lock a row immediately on
voOverAnEntity.executeQuerry() so that the values can be changed and then new values
set. Then the commit() flushes the changes back the DB and the lock is released.
We could write a custom SQLView and in expert mode do the select values,, from abc for update
that would dispatch the DML in real time.
What I'd like though, is for the ViewObjectImpl to support a lock feature?
myEntityVo.setWhereParam();
myEntityVo.lockTheseRows();
myEntityVo.executeQuerry();
Take the values selected, modify and row.setAttribute() ...
with safety since the rows are locked.
... Now I can modify the Rows and let the normal am.comit(); logic go on it's merry way which
is decoupled from my AMmethods.
Thanks, curt

Answer 1

Curt:
Please see my comments on the code snippet (marked with "From Sung:"):
myVo.setWhereClauseParam(0,theWhereValue);
myvo.executeQuerry();
Row myRow = myVo.first();
boolean haveRowLocked = false;
int     maxLoops = 0
while(!haveRowLocked && (maxLoops++ < 3))
  // This is a high concurrency row in this use case
  try {
    myRow.lock()
    haveRowLocked = true;
  } catch (JboException jex)
    // I'll figure out which specific exception is thrown later
    Thread.sleep(10 + (maxLoops * 50));   // sleep a progressively longer time
    continue;
if (!haveRowLocked)
   throw someException;
// Since we just got the lock, I need the latest values in this Row
// Is there any smarter way to do this??
// From Sung: You don't need to refresh the row after lock.
// In the process of lock(), we (BC4J) get the latest values
// for all attributes from the database and push them into
// the row.  Thus, if lock() succeeded, that means you have
// the latest values.
// From Sung: You can the calls to executeQuery() and first()
// myvo.executeQuerry();
// Row myRow = myVo.first();
// Now update the values in this row based on current state
BigDecimal balance = (BigDecimal)myRow.getAttribute ("accountBalance");
balance.add(new BigDecimal("123.45"));
myRow.setAttribute ("accountBalance", newAmt);
transaction.commit();  // update the new Amount and release the lockThanks.
Sung