hello,
I don't know how to solve concurrency problems in a nice way. To fix my updating code I set version control for entity and I check if get OptimisticLockException.

I think this is not the best solution, so I wish to know what is a beter solution for this classic case. I think I should get a record, lock it, update fields and unluck it ... but I don't know how to do it.

Thanks a lot for help


My code for update looks like this (strange enough for only one update):

 while(true){
 boolean ok = true;
 Balance balance = testSessionA.getBalance(id,sleepTime);//sleep used just for testing
 balance.setAmount(balance.getAmount()+10);
 try{
 testSessionA.update(balance);
 }catch(javax.ejb.EJBException ex){
 ex.printStackTrace();
 if(ex.getMessage().equals("javax.persistence.OptimisticLockException")){
 //how many times we should try to update??
 ok = false;
 }
 }
 if(ok){
 break;
 }
 }

@Stateless
@Remote(TestSessionA.class)
@Local(TestSessionA.class)
public class TestSessionABean implements TestSessionA{

 public Balance getBalance(long bId, long sleepTime) throws Exception {
 Balance b = em.find(Balance.class, bId);
 Thread.sleep(sleepTime);//use sleep just to test
 return b;
 }

 public void update(Balance balance) {
 em.merge(balance);

 }

@Entity
public class Balance implements Serializable{

 @Version
 @Column(name = "OPTLOCK")
 public int getVersion() {
 return version;
 }