Java Reference
In-Depth Information
loading the entities, and looking them up by various keys and arguments. All the
methods for creating and looking them up (various
find
methods) are defined in
the home interface and have their parallel versions in the implementation class. If
you are using container-managed persistence, much of this work is done for you.
A
MessageBean
is a message listener that consumes messages from a queue or a
durable subscription. The messages may be sent by any JEE component—from an
application client, another enterprise bean, or a Web component—or from an ap-
plication or system that does not use JEE technology.
C
ONTAINER
S
ERVICES
EJBs can define the following control options at the class or the method level. By
default, the class settings are applied to each method, but an individual method can
define its own setting.
Security:
What rights are required by the client in order to create this class or
perform its methods? EJBs can use the new security model built into Java 2 to
define and control access rights.
Transaction:
What transaction level is supported or required by this bean?
Here are the possibilities:
TX_BEAN_MANAGED
TX_SUPPORTS
TX_NOT_SUPPORTED
TX_REQUIRED
TX_REQUIRES_NEW
TX_MANDATORY
These settings indicate the valid transaction contexts for the bean. (It may be
necessary for the client to first establish a new transaction context in order to
meet the transaction requirements of the bean.)
Isolation level:
What JDBC isolation level does the client require when a read
is performed? The possibilities are TRANSACTION_READ_UNCOMMIT-
TED, TRANSACTION_READ_COMMITTED, TRANSACTION_REPEAT-
ABLE_ READ, and TRANSACTION_SERIALIZABLE.
