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Injects resources. Stores the instance in memory. Executes the requested business method invoked through the business interface by the client. Waits for and executes subsequent client requests. If the client remains idle for a period of time, the container passivates the bean instance. Essentially, passivation means that the bean is moved out of active memory, serialized, and stored in temporary storage. If the client invokes a passivated bean, it is activated (brought back into memory from temporary storage). If the client does not invoke a passivated bean instance for a period of time, it is destroyed. If the client requests the removal of a bean instance, it is first activated if necessary and then destroyed.

Figure 3.8 The lifecycle of a stateful session bean. A stateful bean maintains client state and cannot be pooled. It may be passivated when the client is not using it and must be activated when the client needs it again.

Like a stateless session bean, the stateful session bean has lifecycle callback methods, or callbacks, that are invoked when the PostConstruct event occurs (as an instance is created) and when the PreDestroy event occurs (before the instance is destroyed). But now we have two new callback events for which we can have callbacks: PrePassivate and PostActivate, which are part of the passivation process. We ll discuss them next. Just as in listing 3.1, we use a PostConstruct callback in listing 3.2 to open a database connection from the injected data source so that it can be used by business methods. Also as in listing 3.1, we close the cached connection in preparation for bean destruction in a PreDestroy callback. However, you should note that we invoke the very same method for both the PreDestroy and PrePassivate callbacks:

UserTransaction transaction = ejbContext.getUserTransaction(); transaction.begin(); try { //perform business logic here } catch( Exception e ) { boolean errorFixed = false; boolean markedForRollback = transaction.getRollbackOnly(); if( !markedForRollback ) //not marked for rollback { //discover actual error and attempt a fix errorFixed = fixError(); Attempts to fix } the error else return; //skip remaining method body if( !errorFixed ) { transaction.rollback(); } } transaction.commit();

public aspect FrontController { static Hashtable pathInfoCommandMap = new Hashtable(); static {

@PrePassivate @PreDestroy public void cleanup() { ... }

Similarly, the exact same action is taken for both the PostConstruct and PostActivate callbacks:

For container-managed transaction beans Listing 5.3 contains a code section from a CMT bean business method that attempts to avoid a rollback.

@PostConstruct @PostActivate public void openConnection() { ... }

15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 }

To see why this is the case, let s discuss activation and passivation in a little more detail. Passivation and activation If clients don t invoke a bean for a long enough time, it is not a good idea to continue keeping it in memory. For a large number of beans, this could easily make the machine run out of memory. The container employs the technique of passivation to save memory when possible.

Ltry { //perform business logic here } catch( Exception e ) { boolean errorFixed = false; boolean markedForRollback = ejbContext.getRollbackOnly(); if( !markedForRollback ) Tests for a potential rollback { //discover actual error and attempt a fix

Passivation essentially means saving a bean instance into disk instead of holding it in memory. The container accomplishes this task by serializing the entire bean instance and moving it into permanent storage like a file or the database. Activation is the opposite of passivation and is done when the bean instance is needed again. The container activates a bean instance by retrieving it from permanent storage, deserializing it, and moving it back into memory. This means that all bean instance

variables that you care about and should be saved into permanent storage must either be a Java primitive or implement the java.io. Serializable interface.

errorFixed = fixError(); Attempts to fix the error } else return; //skip remaining method body if( !errorFixed ) { ejbContext.setRollbackOnly(); } }

pathInfoCommandMap.put("/logon","aop.j2ee.[...].LoginController"); pathInfoCommandMap.put("/subscribe","aop.j2ee.[...].SubscribeController"); } pointcut trapApplicationController(String aRequestPathInfo, HttpServletRequest aRequest, HttpServletResponse aResponse): call(private String FrontController.invokeApplicationController( String,HttpServletRequest,HttpServletResponse) throws Exception) && args(aRequestPathInfo,aRequest,aResponse); String around(String aRequestPathInfo, HttpServletRequest aRequest, HttpServletResponse aResponse) throws Exception: trapApplicationController(aRequestPathInfo, aRequest,aResponse) { ApplicationController controller = null; String className = (String)pathInfoCommandMap.get(aRequestPathInfo); if(className != null) { Class controllerClass = Class.forName(className); controller = (ApplicationController)controllerClass.newInstance(); if(controller != null) { RequestContextFactory factory = RequestContextFactory.getInstance(); RequestContext context = factory.getRequestContext(aRequest); aRequestPathInfo = (String)controller.process(context); } } return aRequestPathInfo; }