CMP versus CMT

[Nath White]

I understand what Container/Bean Managed Persistence are about, but what are Container/Bean Managed Transactions?
According to the Whizz Labs tests, CMP and CMT are different things.
Additionally, it seems to suggest that CMT might be necessary even if no data is being persisted. What kind of transaction is required if there is no data persistence??

[Shankar Ranganathan]

I will tell in you short what is CMT.
When it is CMT all your commits and rollback are taken care of by container or in other words you don't have to explicitly write commit and rollback,in the case of bmt you have to do that.
My suggestion you can thru the ejb spec or edroman book for further details
Shankar

[Ajith Kallambella]

CMP - Container Managed Persistence

Entity beans are mapped to tables using mapping tools provided by the container.

Container takes care of generating SQL statements and persisting bean state to database.

Programmer will not implement ejbLoad() and ejbStore().

No fine-grained control over SQL statements.

Rapid development, heavy deployment activities.

Alternative - BMP - Bean Managed Persistence.

CMT - Container Managed Transaction(s)

Where a bean method is transaction enabled in the deployment descriptor, container takes care of initiating, propagating, commiting and rolling back the transaction.

Alternative - BMT - Bean Managed Transaction(s).

Uses Java Transaction Service(JTS)

Programmer will not use explicit JTA transaction calls in the code.

Less error prone compared to BMT.

[Rama Raghavan]

CMT
- Transaction in Entity beans are (almost) always Container managed
- Transactions in Session beans may be bean or container managed
Rama

[Chris Mathews]

Originally posted by Rama Raghavan:
- Transaction in Entity beans are (almost) always Container managed

Actually, there is no almost about it. Entity Beans will always be CMT.

Section 17.3.1 of the EJB 2.0 Specification
An Entity Bean must always be designed with container-managed transaction demarcation.

[Nath White]

Actually, there is no almost about it. Entity Beans will always be CMT.

In EJB 1.0, session and entity beans can both be BMT.
In EJB 1.1, only session beans can be BMT.
In either case only beans set to have BMP can declare BMT. (both persistence and transaction must be declared at the bean level rather than method level)
phew! Thanks for the pointers guys. When I first read about it in my EJB book I didn't see the distinction, but it all makes sense now.