org.dvb.application.AppsDatabase Maven / Gradle / Ivy
package org.dvb.application;
import java.util.*;
/**
* The AppsDatabase is an abstract view of the currently
* available applications. The entries will be provided by the
* application manager, and gleaned from the AIT signaling.
* When the service context in which an application is running undergoes
* service selection, instances of AppsDatabase used by that application
* shall be updated from the new service before an AppsDatabaseEvent
* is sent to the newDatabase method of any registered
* AppsDatabaseEventListeners.
* For applications fully signalled in the current service (i.e. excluding
* externally authorised ones), the attributes entries shall be the ones from
* the signalling of the current service even if the application was originally
* launched from another service and then survived service selection. For running
* externally authorised applications, the entries will be those from the last service
* in which they ran fully signalled.
* Externally authorized applications shall not appear unless
* an instance of that application is actually running.
*
A generic launcher may be written which uses the database to display
* information in AppAttributes and uses an AppProxy to launch it
*
Methods on classes in this package do not block, they return the
* information the system currently has. Therefore applications should be
* aware that data may be stale, to within one refresh period of the AIT.
* e.g.:
*
*
* AppsDatabase theDatabase = AppsDatabase.getDatabase();
* if (theDatabase != null ) {
* Enumeration attributes = theDatabase.getAppAttributes();
* if(attributes != null) {
* while(attributes.hasMoreElements()) {
* AppAttributes info ;
* AppProxy proxy ;
*
* info = (AppAttributes)attributes.nextElement();
* proxy = (AppProxy)theDatabase.getAppProxy(info.getIdentifier());
* URL icon = info.getIcon();
* // blah blah..
* // lets start it.
* proxy.start(false, null);
* }
* }
* }
*
*
* Where methods on this class as specified as working on "available" applications or
* "currently available" applications the following definition shall apply.
* An application is "currently available" if and only if one of the following
* applies in the service context within which the application calling the method
* is executing and the visibility of the application is not '00'..
* - it is signalled as being present or autostart in the currently selected
* service of that service context and could be started.
*
- it is currently running in that service context.
*
* In addition to the methods listed below, all calls made using an
* AppsDatabaseFilter shall only use that filter to test "currently available"
* applications as defined here.
* Applications whose information (e.g. signaling) is invalid
* (e.g. one or more mandatory descriptors are missing or incorrect) may not be listed in the AppsDatabase.
* Where applications are signalled in a broadcast AIT and the MHP terminal
* tunes away from the service on which the AIT is carried, but
* without selecting a new service, the AppsDatabase shall retain
* the entries as signalled in that AIT until a new service is selected.
*/
public class AppsDatabase {
/**
* This constructor is provided for the use of implementations and specifications
* which extend the present document. Applications shall not define sub-classes of
* this class. Implementations are not required to behave correctly if any such
* application defined sub-classes are used.
*/
protected AppsDatabase() {
}
/**
* Returns the singleton AppsDatabase object.
* The AppsDatabase is either a singleton for each MHP application or a singleton for the MHP terminal.
* @return the singleton AppsDatabase object.
* @since MHP1.0
*/
static public AppsDatabase getAppsDatabase() {
return null ;
}
/**
* Returns the number of applications currently available.
*
* @return the number of applications currently available.
* @since MHP1.0
*/
public int size() {
return 0 ;
}
/**
* Returns an enumeration of the application IDs available.
* The Enumeration will contain the set of AppID that match the filtering
* criteria.
* For implementations conforming to this version of the specification,
* only CurrentServiceFilter or RunningApplicationsFilter
* filters may return a non empty Enumeration. If the filter object is not an
* instance of CurrentServiceFilter or RunningApplicationsFilter
* or one of their subclasses then,
* the method shall return an empty Enumeration.
*
* This method will return an empty Enumeration if there are no matching applications.
* @param filter the filter to apply
*
* @return the applications available matching the filtering criteria
* @since MHP1.0
*/
public Enumeration getAppIDs(AppsDatabaseFilter filter) {
return null ;
}
/**
* Returns an enumeration of AppAttributes of the applications available.
* The Enumeration will contain the set of AppAttributes that satisfy the filtering
* criteria.
* For implementations conforming to this version of the specification, only CurrentServiceFilter or RunningApplicationsFilter
* filters may return a non empty Enumeration. If the filter object is not an
* instance of CurrentServiceFilter or RunningApplicationsFilter or a subclass of either then,
* the method shall return an empty Enumeration.
* This method shall return instances which reflect the contents of the database
* at the time the method is called. After an AppsDatabaseEvent has been
* generated, new instances may be returned. After a service selection has taken
* place, applications which survived the service selection may call this method
* in order to discover the attributes of the applications signalled on the new
* service.
* This method will return an empty Enumeration if there are no attributes.
* @param filter the filter to apply
* @return an enumeration of the applications attributes.
* @since MHP1.0
*/
public Enumeration getAppAttributes(AppsDatabaseFilter filter) {
return null ;
}
/**
* Returns the properties associated with the given ID. Returns null if
* no such application is available.
*
Only one AppAttributes object shall be returned in the case where there are
* several applications having the same (organisationId, applicationId) pair.
* In such a case, the same algorithm as would be used to autostart such applications
* shall be used to decide between the available choices by the implementation.
* This method shall return instances which reflect the contents of the database
* at the time the method is called. After an AppsDatabaseEvent has been
* generated, new instances may be returned. After a service selection has taken
* place, applications which survived the service selection may call this method
* in order to discover the attributes of the applications signalled on the new
* service.
*
* @return the value to which the key is mapped in this dictionary if AppId
* corresponds to an application which is either a currently available application
* or remote application or both. Null otherwise.
* @param key an application ID.
* @since MHP1.0
*/
public AppAttributes getAppAttributes (AppID key) {
return null;
}
/**
* Returns the ApplicationProxy
* associated with the given ID. Returns null if no such application
* available.
*
Only one AppProxy object shall be returned in the case where there are
* several applications having the same (organisationId, applicationId) pair.
* In such a case, the same algorithm as would be used to autostart such applications
* shall be used to decide between the available choices by the implementation.
*
If an application has an application instance in the destroyed state then a
* proxy for that appplication instance shall not be retrieved. Instead, what
* shall be retrieved is a proxy for another application instance which shall
* be in the not loaded state unless that application instance has already been started.
*
* @return the AppProxy associated with the key parameter or null if the key
* is not an application ID, or not mapped to any application available.
* @param key an application ID
* @throws SecurityException shall not be thrown for AppIDs which are returned
* by getAppIDs(CurrentServiceFilter) or getAppIDs(RunningApplicationsFilter)
* @since MHP1.0
*/
public AppProxy getAppProxy(AppID key) {
return null;
}
/**
* Add a listener to the database so that an application can be informed
* if the database changes.
*
* @param listener the listener to be added.
* @since MHP1.0
*/
public void addListener(AppsDatabaseEventListener listener){
}
/**
* remove a listener on the database.
*
* @param listener the listener to be removed.
* @since MHP1.0
*/
public void removeListener(AppsDatabaseEventListener listener){
}
}