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Appendix B. State and Sequence Diagrams

This appendix contains state and sequence diagrams for all the bean types discussed in this book: container-managed and bean-managed entity beans, stateless and stateful session beans, and message-driven beans. Although standard Unified Modeling Language (UML) is used in these diagrams, some extensions were required to model EJB runtime characteristics. In the state diagrams, for example, callback methods and class instantiation operations are shown as part of the transition event.

In the sequence diagrams, container-provided classes such as the container itself, the EJB object, and the EJB home are shown as separate classes but are also boxed together. Messages sent from classes in the container system box are considered to be sent from the container system as a whole, not necessarily from the specific container-provided class. This generalization is necessary because the container's interaction with the bean is characterized by these classes but differs from one vendor's implementation to the next. The exact source of the message is immaterial, as long as you realize that the container system sent it.

B.1 Entity Beans

B.1.1 Life Cycle State Diagram of the Entity Bean

Figure B-1. Life-cycle state diagram of the entity bean

figs/ejb3_ab01.gif

B.1.2 Sequence Diagrams for Container-Managed Persistence

Figure B-2. Creation and removal in container-managed persistence

figs/ejb3_ab02.gif

Figure B-3. Activation and synchronization in container-managed persistence

figs/ejb3_ab03.gif

B.1.3 Sequence Diagrams for Bean-Managed Persistence

Figure B-4. Creation and removal in bean-managed persistence

figs/ejb3_ab04.gif

Figure B-5. Activation and synchronization in bean-managed persistence

figs/ejb3_ab05.gif

Table B-1 summarizes the operations an entity bean is allowed to perform in various stages of its life cycle. The allowed operations are the same for EJB 2.0 and 1.1, except for the EntityContext methods getEJBLocalHome() and getEJBLocalObject() and the operations allowed for ejbHome() methods, which are specific to EJB 2.0.

Table B-1. Allowed operations for entity beans

Method

Allowed operations

setEntityContext()

unsetEntityContext()

EntityContext methods:

getEJBHome()

getEJBLocalHome()

JNDI ENC contexts:

Properties: java:comp/env

ejbCreate()

ejbFind()

ejbHome()

EntityContext methods:

getEJBHome()

getEJBLocalHome()

getCallerPrincipal()

isCallerInRole()

getRollbackOnly()

setRollbackOnly()

JNDI ENC contexts:

Properties: java:comp/env

Resource managers: java:comp/env/jdbc

EJB references: java:comp/env/ejb

ejbPostCreate()

ejbLoad()

ejbStore()

ejbRemove()

Business methods

EntityContext methods:

getEJBHome()

getEJBLocalHome()

getCallerPrincipal()

isCallerInRole() getRollbackOnly()

setRollbackOnly()

getEJBObject()

getEJBLocalObject()

getPrimaryKey()

JNDI ENC contexts:

Properties: java:comp/env

Resource managers: java:comp/env/jdbc

EJB references: java:comp/env/ejb

ejbActivate()

ejbPassivate()

EntityContext methods:

getEJBHome()

getEJBLocalHome()

getEJBObject()

getEJBLocalObject()

getPrimaryKey()

JNDI ENC contexts:

Properties: java:comp/env

Note that entity beans can never access the EJBContext.getUserTransaction() method, because entity beans are not allowed to manage their own transactions. Only session beans can access this method.

B.2 Session Beans

B.2.1 Stateless Session Beans

Figure B-6. Life-cycle state diagram of the stateless session bean

figs/ejb3_ab06.gif

Figure B-7. Creation and removal of stateless session beans

figs/ejb3_ab07.gif

Table B-2 summarizes the operations that are legal for a stateless session bean. The allowed operations are the same for both EJB 2.0 and 1.1, except for the SessionContext methods getEJBLocalHome() and getEJBLocalObject(), which are specific to EJB 2.0.

Table B-2. Allowed operations for stateless session beans

Method

Allowed operations

 

Container-managed transactions

Bean-managed transactions

ejbCreate()

ejbRemove()

EntityContext methods:

getEJBHome()

getEJBLocalHome()

getEJBObject()

getEJBLocalObject()

JNDI ENC contexts:

Properties: java:comp/env

EntityContext methods:

getEJBHome()

getEJBLocalHome()

getEJBObject()

getEJBLocalObject()

getUserTransaction()

JNDI ENC contexts:

Properties: java:comp/env

Business methods

EntityContext methods:

getEJHome()

getEJBLocalHome()

getCallerPrincipal()

isCallerInRole()

getRollbackOnly()

setRollbackOnly()

getEJBObject()

getEJBLocalObject()

JNDI ENC contexts:

Properties: java:comp/env

Resource managers: java:comp/env/jdbc

EJB references: java:comp/env/ejb

EntityContext methods:

getEJHome()

getEJBLocalHome()

getCallerPrincipal()

isCallerInRole()

getEJBObject()

getEJBLocalObject()

getUserTransaction()

JNDI ENC contexts:

Properties: java:comp/env

Resource managers: java:comp/env/jdbc

EJB references: java:comp/env/ejb

ejbActivate()

ejbPassivate()

Not supported (stateless beans do not use these methods)

Not supported (stateless beans do not use these methods)

B.2.2 Stateful Session Beans

Figure B-8. Life-cycle state diagram of the stateful session bean

figs/ejb3_ab08.gif

Figure B-9. Life cycle of a stateful session bean with the SessionSynchronization interface

figs/ejb3_ab09.gif

Figure B-10. Creation and removal of stateful session beans

figs/ejb3_ab10.gif

Figure B-11. Activation process of stateful session beans

figs/ejb3_ab11.gif

Figure B-12. Transaction notification in SessionSynchronization session beans

figs/ejb3_ab12.gif

Table B-3 summarizes the operations that are legal for a stateful session bean. The allowed operations are the same for both EJB 2.0 and 1.1, except for the SessionContext methods getEJBLocalHome() and getEJBLocalObject(), which are specific to EJB 2.0.

Table B-3. Allowed operations for stateful session beans

Method

Allowed operations

 

Container-managed transactions

Bean-managed transactions

setSessionContext()

EntityContext methods:

getEJBHome()

getEJBLocalHome()

JNDI ENC contexts:

Properties: java:comp/env

EntityContext methods:

getEJBHome()

getEJBLocalHome()

JNDI ENC contexts:

Properties: java:comp/env

ejbCreate()

ejbRemove()

ejbActivate()

ejbPassivate()

EntityContext methods:

getEJBHome()

getEJBLocalHome()

getCallerPrincipal()

isCallerInRole()

getEJBObject()

getEJBLocalObject()

JNDI ENC contexts:

Properties: java:comp/env

Resource managers: java:comp/env/jdbc

EJB references: java:comp/env/ejb

EntityContext methods:

getEJBHome()

getEJBLocalHome()

getCallerPrincipal()

isCallerInRole()

getEJBObject()

getEJBLocalObject()

getUserTransaction()

JNDI ENC contexts:

Properties: java:comp/ env

Resource managers: java:comp/env/jdbc

EJB references: java:comp/env/ejb

Business methods

EntityContext methods:

getEJBHome()

getEJBLocalHome()

getCallerPrincipal()

isCallerInRole()

getRollbackOnly()

setRollbackOnly()

getEJBObject()

getEJBLocalObject()

JNDI ENC contexts:

Properties: java:comp/env

Resource managers: java:comp/env/jdbc

EJB references: java:comp/env/ejb

EntityContext methods:

getEJHome()

getEJBLocalHome()

getCallerPrincipal()

isCallerInRole()

getEJBObject()

getEJBLocalObject()

getUserTransaction()

JNDI ENC contexts:

Properties: java:comp/env

Resource managers: java:comp/env/jdbc

EJB references: java:comp/env/ejb

afterBegin()

beforeCompetion()

EntityContext methods:

getEJBHome()

getEJBLocalHome()

getCallerPrincipal()

isCallerInRole()

getRollbackOnly()

setRollbackOnly()

getEJBObject()

getEJBLocalObject()

JNDI ENC contexts:

Properties: java:comp/env

Resource managers: java:comp/env/jdbc

EJB references: java:comp/env/ejb

Not supported (bean-managed transaction beans cannot implement the SessionSynchronization interface)

afterCompletion()

EntityContext methods:

getEJBHome()

getEJBLocalHome()

getCallerPrincipal()

isCallerInRole()

getEJBObject()

getEJBLocalObject()

JNDI ENC contexts:

Properties: java:comp/env

Not supported (bean-managed transaction beans cannot implement the SessionSynchronization interface)

B.2.3 Message-Driven Beans

Figure B-13. Message-driven bean life-cycle state diagram

figs/ejb3_ab13.gif

Figure B-14. Message-driven bean sequence diagram

figs/ejb3_ab14.gif

B.2.4 Interactions Between Exceptions and Transactions

Table B-4 summarizes what happens to a transaction if an exception is thrown while the transaction is in process.

Table B-4. Exception summary for session and entity beans

Transaction scope

Transaction type attributes

Exception thrown

Container's action

Client's view

Client-initiated transaction.

The transaction is started by the client (application or EJB) and is propagated to the enterprise bean method.

transaction-type =

Container

transaction-attribute =

Required |

Mandatory |

Supports

Application exception

If the EJB invoked setRollbackOnly(), mark the client's transaction for rollback.

Rethrow the application exception.

Receives the application exception. The client's transaction may or may not have been marked for rollback.

   

System exception

Mark the client's transaction for rollback.

Log the error.

Discard the instance.

Rethrow the JTA TransactionRolledbackException to remote clients or the javax.ejb.TransactionRolledbackLocalException to EJB 2.0 local clients.

Remote clients receive the JTA TransactionRolledbackException; local clients receive the javax.ejb.TransactionRolledbackLocalException.

The client's transaction has been rolled back.

Container-initiatedtransaction.

The transaction started when the EJB's method was invoked and will end when the method completes.

transaction-type =

Container

transaction-attribute =

Required |

RequiresNew

Application exception

If the EJB invoked setRollbackOnly(), roll back the transaction and rethrow the application exception.

If the EJB did not explicitly roll back the transaction, attempt to commit the transaction and rethrow the application exception.

Receives the application exception. The EJB's transaction may or may not have been rolled back. The client's transaction is not affected.

   

System exception

Roll back the transaction.

Log the error.

Discard the instance.

Rethrow the RemoteException to remote clients or the EJBException to EJB 2.0 local clients.

Remote clients receive the RemoteException; local EJB 2.0 clients receive the EJBException.

The EJB's transaction was rolled back.

The client's transaction may or may not be marked for rollback, depending on the vendor.

The bean is not part of a transaction.

The EJB was invoked but does not propagate the client's transaction and does not start its own transaction.

transaction-type =

Container

transaction-attribute =

Never |

NotSupported |

Supports |

Application exception

Rethrow the application exception.

Receives the application exception.

The client's transaction is not affected.

   

System exception

Log the error.

Discard the instance.

Rethrow the RemoteException to remote clients or the EJBException to EJB 2.0 local clients.

Remote clients receive the RemoteException; local EJB 2.0 clients receive the EJBException.

The client's transaction may or may not be marked for rollback, depending on the vendor.

Bean-managed transaction.

The stateful or stateless session EJB uses the EJBContext to explicitly manage its own transaction.

transaction-type =

Bean

transaction-attribute =

Bean-managed transaction EJBs do not use transaction attributes.

Application exception

Rethrow the application exception.

Receives the application exception.

The client's transaction is not affected.

   

System exception

Roll back the transaction.

Log the error.

Discard the instance.

Rethrow the RemoteException to remote clients or the EJBException to EJB 2.0 local clients.

Remote clients receive the RemoteException; local EJB 2.0 clients receive the EJBException.

The client's transaction is not affected.

Table B-5 summarizes the interactions between different types of exceptions and transactions in message-driven beans.

Table B-5. Exception summary for message-driven beans

Transaction scope

Transaction type attributes

Exception thrown

Container's action

Container-initiated transaction.

The transaction started before the onMessage() method was invoked and will end when the method completes.

transaction-type =

Container

transaction-attribute =

Required

System exception

Roll back the transaction.

Log the error.

Discard the instance.

Container-initiated transaction.

No transaction was started.

transaction-type =

Container

transaction-attribute =

NotSupported

System exception

Log the error.

Discard the instance.

Bean-managed transaction.

The message-driven bean uses the EJBContext to explicitly manage its own transaction.

transaction-type =

Bean

transaction-attribute =

Bean-managed transaction EJBs do not use transaction attributes.

System exception

Roll back the transaction.

Log the error.

Discard the instance.

 

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