EJB 3.1 [8]

Timer Service

A timer is associated with the bean that created it and it calls it's ejbTimeout(Timer timer)/@Timeout method when it goes off.
Since EJB 3.1 there is a ScheduleExpression class that allows to define when timer should be fired. There is also @Schedule annotation, that alows to achieve the same in a declarative manner.
EJB must implement TimedObject interface to use Timer Service.
TimerService can be accessed with sessionContext.getTimerService() method. You can create a timer with timerService.createXxxTimer() call (it can create SingleAction, Interval ands Calendar timers).
Alternatively, you can do it in declarative manner with @Schedule annotation:


Timers are persistent - they will be restored if the system crashes. It isn't clear what will happen with the interval timers that would go off several times while the system is down (they may catch up just after the startup).

Timers can be cancelled. To reschedule a timer you cancel it and create a new one. Timer created in the rolledback transaction scope will get uncreated.

Web Services

WIth JAX-RPC there is a lot to define (WSDL, JAX_RPC mapping file and webservices.xml). with JAX-WS all you need is @WebService and @WebMethod annotations.
When there is no @WebMethod annotation - all methods of bean annotated with @WebService are exposed.
@SOAPBinding annotation allows you to customize WS: style: DOCUMENT/RPC, use: LITERAL/ENCODED(do not use), parameterStyle: BARE/WRAPPED.
@WebParam can be placed on parameters (with name and mode: IN/OUT/INOUT attributes). @WebResult is the same for return value.
@OneWay annotation for methods that do not return response allows server to call it asynchronously (if it wishes to).
@WebService annotation has endpointInterface attribute, that allows to separate interface from implementation. We plece @WebService annotation on both the interface and the implementation then.

There is a @WebServiceRef that allows to inject a service class or an endpoint (the annotation would take the service class as an argument then).