javax.tv.service.selection

Interface ServiceContext

All Known Subinterfaces:

DvbServiceContext

All Known Implementing Classes:

ServiceContextImpl

public interface ServiceContext

A ServiceContext represents an environment in which services are presented in a broadcast receiver. Applications may use ServiceContext objects to select new services to be presented. Content associated with a selected service is presented by one or more ServiceContentHandler objects managed by the ServiceContext.

A ServiceContext can exist in four states - presenting, not presenting, presentation pending and destroyed. The initial state is not presenting.

The select() method can be called from any state except destroyed. Assuming no exception is thrown, the service context then enters the presentation pending state. No event is generated on this state transition. If a call to select() completes successfully, either a NormalContentEvent or an AlternativeContentEvent is generated and the ServiceContext moves into the presenting state.

If the selection operation fails, a SelectionFailedEvent is generated. If the select() method is called during the presentation pending state, a SelectionFailedEvent with reason code INTERRUPTED is generated, and the ServiceContext will proceed in the presentation pending state for the most recent select() call. Otherwise, if the state before the failed select operation was not presenting, the ServiceContext will return to that state and a PresentationTerminatedEvent be generated. If the state before the failed select operation was presenting, it will attempt to return to that previous state, which can result in a NormalContentEvent or AlternativeContentEvent if this is possible, or a PresentationTerminatedEvent if it is not possible.

The not presenting state is entered due to service presentation being stopped which is reported by a PresentationTerminatedEvent. The stopping of service presentation can be initiated by an application calling the stop() method or because some change in the environment makes continued presentation impossible.

The destroyed state is entered by calling the destroy() method, and is signaled by a ServiceContextDestroyedEvent. Once this state is entered, the ServiceContext can no longer be used for any purpose. A destroyed ServiceContext will be eligible for garbage collection once all references to it by any applications have been removed.

Note that the ability to select a service for presentation does not imply exclusive rights to the resources required for that presentation. Subsequent attempts to select the same service may fail.

Applications may also use this interface to register for events associated with ServiceContext state changes.

See Also:

Service, ServiceContentHandler, NormalContentEvent, AlternativeContentEvent, SelectionFailedEvent, PresentationTerminatedEvent, ServiceContextDestroyedEvent, ServiceContextListener

Method Summary

Methods

Modifier and Type	Method and Description
void	addListener(ServiceContextListener listener) Subscribes a listener to receive events related to this ServiceContext.
void	destroy() Causes the ServiceContext to release all resources and enter the destroyed state.
Service	getService() Reports the Service being presented in this ServiceContext.
ServiceContentHandler[]	getServiceContentHandlers() Reports the current collection of ServiceContentHandlers.
void	removeListener(ServiceContextListener listener) Unsubscribes a listener from receiving events related to this ServiceContext.
void	select(Locator[] components) Selects content by specifying the parts of a service to be presented.
void	select(Service selection) Selects a service to be presented in this ServiceContext.
void	stop() Causes the ServiceContext to stop presenting content and enter the not presenting state.

Method Detail

select

void select(Service selection)
            throws SecurityException

Selects a service to be presented in this ServiceContext. If the ServiceContext is already presenting content, the new selection replaces the content being presented. If the ServiceContext is not presenting, successful conclusion of this method results in the ServiceContext entering the presenting state.

This method is asynchronous and successful completion of the selection is notified by either a NormalContentEvent or a AlternativeContentEvent. If an exception is thrown when this method is called, the state of the service context does not change. In such a case, any service being presented before this method was called will continue to be presented.

If the selection process fails after this method returns, a SelectionFailedEvent will be generated. In this case, the system will attempt to return to presenting the original service (if any). If this is not possible (due, for example, to issues such as tuning or CA) the ServiceContext will enter the not presenting state and a PresentationTerminatedEvent will be generated.

If the ServiceContext is currently presenting a service and components of the current service are also to be presented in the newly selected service, these components will continue to be presented and will not be restarted. If the calling application is not a part of the newly selected service and the application lifecycle policy on the receiver dictates that the calling application be terminated, termination of the application will be affected through the application lifecycle API.

If the provided Service is transport-independent, this method will resolve the Service to a transport-dependent Service before performing the selection. The actual Service selected will be reported through the getService() method.

Successful completion of a select operation using this method provides ServiceContentHandler instances for all components that are signaled as "auto-start" in the selected service. Upon entering the presenting state, these ServiceContentHandler instances will have begun presenting their respective content; ServiceMediaHandler instances will be in the started state.

Parameters:

selection - The Service the service to be selected.

Throws:

SecurityException - If the caller owns this ServiceContext but does not have SelectPermission(selection.getLocator(), "own"), or if the caller does not own this ServiceContext and does not have SelectPermission(selection.getLocator(), "*").

IllegalStateException - If the ServiceContext has been destroyed.

See Also:

NormalContentEvent, AlternativeContentEvent, SelectionFailedEvent, PresentationTerminatedEvent, Service, getService(), ServiceContentHandler, destroy()

select

void select(Locator[] components)
            throws InvalidLocatorException,
                   InvalidServiceComponentException,
                   SecurityException

Selects content by specifying the parts of a service to be presented. If the ServiceContext is already presenting content, the new selection replaces the content being presented. If the ServiceContext is not presenting, successful conclusion of this method results in the ServiceContext entering the presenting state.

This method is asynchronous and successful completion of the selection is notified by either a NormalContentEvent or a AlternativeContentEvent. If failure of the selection can be determined when this method is called, an exception will be generated and the state of the ServiceContext will not change. In this case, any service being presented before this method was called will continue to be presented.

If failure of the selection is determined after this method returns, a SelectionFailedEvent will be generated. In this case, the implementation of the method will try to return to presenting the original service (if any). If this is not possible (due, for example, to issues such as tuning or CA) the ServiceContext will enter the not presenting state and a PresentationTerminatedEvent will be generated.

If the ServiceContext is currently presenting a service and components of the current service are also to be presented in the newly selected content, these components will continue to be presented and will not be restarted. If the calling application is not a part of the newly selected content and the application lifecycle policy on the receiver dictates that the calling application be terminated, termination of the application will be affected through the application lifecycle API.

Successful completion of a selection operation using this method provides ServiceContentHandlers for those components indicated in the components parameter which were successfully presented. Upon entering the presenting state, these ServiceContentHandler instances will have begun presenting their respective content; ServiceMediaHandler instances will be in the started state. This method will not provide ServiceContentHandler instances for service components for which a locator is not specified. If the content corresponding to any of the locators specified can be successfully presented then the selection operation shall be considered to have succeeded even if attempts to present content corresponding to other locators failed. If different locators failed for different reasons then the reason code is implementation dependent.

Parameters:

components - An array of Locator instances representing the parts of this service to be selected. Each array element must be a locator to either a ServiceComponent or content within a service component (such as an Xlet).

Throws:

InvalidLocatorException - If a Locator provided does not reference a selectable service component or selectable content within a service component. For locators which reference a service component which is not selectable and where there is no ServiceContentHandler defined, the exception shall be thrown if the error condition can be detected without causing the method to block. For example, implementations shall not block waiting for network access or tuning where this is required to discover whether a specific locator references a selectable service component and there is a ServiceContentHandler. Where such an error condition is discovered after the return from this method, a SelectionFailedEvent with reason code MISSING_HANDLER shall be generated.

InvalidServiceComponentException - If a specified service component must be presented in conjunction with another service component not contained in components, if the specified components are not all members of the same service, or if the specified set of components cannot be presented as a coherent whole.

SecurityException - If, for any valid i, the caller owns this ServiceContext but does not have SelectPermission(components[i], "own"), or if the caller does not own this ServiceContext and does not have SelectPermission(components[i], "*").

IllegalStateException - If the ServiceContext has been destroyed.

See Also:

NormalContentEvent, AlternativeContentEvent, SelectionFailedEvent, PresentationTerminatedEvent, ServiceContentHandler, ServiceComponent

stop

void stop()
          throws SecurityException

Causes the ServiceContext to stop presenting content and enter the not presenting state. Resources used in the presentation will be released, associated ServiceContentHandlers will cease presentation (ServiceMediaHandlers will no longer be in the started state), and a PresentationTerminatedEvent will be posted.

This operation completes asynchronously. No action is performed if the ServiceContext is already in the not presenting state.

Throws:

SecurityException - If the caller owns this ServiceContext but does not have ServiceContextPermission("stop", "own"), or if the caller does not own this ServiceContext and does not have SelectPermission("stop", "*").

IllegalStateException - If the ServiceContext has been destroyed.

destroy

void destroy()
             throws SecurityException

Causes the ServiceContext to release all resources and enter the destroyed state. This method indicates that the the ServiceContext must cease further activity, and that it will no longer be used. After completion of this method, ServiceMediaHandler instances associated with this ServiceContext will have become unrealized or will have been closed. If the ServiceContext is currently in the presenting or presentation pending state, this method will first stop the ServiceContext, causing a PresentationTerminatedEvent to be posted. After the ServiceContext has moved to the destroyed state, a ServiceContextDestroyedEvent will be posted.

This operation completes asynchronously. No action is performed if the ServiceContext is already in the destroyed state.

Throws:

SecurityException - If the caller does not have permission to call stop() on this ServiceContext, or if the caller owns this ServiceContext but does not have ServiceContextPermission("destroy", "own"), or if the caller does not own this ServiceContext and does not have SelectPermission("destroy", "*").

See Also:

stop()

getServiceContentHandlers

ServiceContentHandler[] getServiceContentHandlers()
                                                  throws SecurityException

Reports the current collection of ServiceContentHandlers. A zero-length array is returned if the ServiceContext is in in the not presenting or presentation pending states. When a service with no components is selected, the ServiceContext shall generate a NormalContentEvent and enter the PRESENTING state. NOTE 1: A zero length array may also be returned if the currently selected service has no components at all. For example, a service which is only on-air for part of day and presently has no video, audio or applications. NOTE 2: Applications cannot assume anything about the order of the ServiceContentHandlers returned by this method.

Returns:

The current ServiceContentHandler instances.

Throws:

SecurityException - If the caller owns this ServiceContext but does not have ServiceContextPermission("getServiceContentHandlers", "own"), or if the caller does not own this ServiceContext and does not have SelectPermission("getServiceContentHandlers", "*").

IllegalStateException - If the ServiceContext has been destroyed.

getService

Service getService()

Reports the Service being presented in this ServiceContext. If the ServiceContext is currently presenting a service, the Service returned will be a network-dependent representation of the Service indicated in the last successful select() method call. If the ServiceContext is not in the presenting state then null is returned.

Returns:

The service currently being presented.

Throws:

IllegalStateException - If the ServiceContext has been destroyed.

addListener

void addListener(ServiceContextListener listener)

Subscribes a listener to receive events related to this ServiceContext. If the specified listener is currently subscribed, no action is performed.

Parameters:

listener - The ServiceContextListener to subscribe.

Throws:

IllegalStateException - If the ServiceContext has been destroyed.

See Also:

ServiceContextEvent

removeListener

void removeListener(ServiceContextListener listener)

Unsubscribes a listener from receiving events related to this ServiceContext. If the specified listener is not currently subscribed, no action is performed.

Parameters:

listener - The ServiceContextListener to unsubscribe.

Throws:

IllegalStateException - If the ServiceContext has been destroyed.