public interface FlagTracker
An implementation of this interface is returned by LDClientInterface.getFlagTracker()
.
Application code never needs to implement this interface.
Modifier and Type | Method and Description |
---|---|
void |
addFlagChangeListener(FlagChangeListener listener)
Registers a listener to be notified of feature flag changes in general.
|
FlagChangeListener |
addFlagValueChangeListener(java.lang.String flagKey,
LDUser user,
FlagValueChangeListener listener)
Registers a listener to be notified of a change in a specific feature flag's value for a specific set of
user properties.
|
void |
removeFlagChangeListener(FlagChangeListener listener)
Unregisters a listener so that it will no longer be notified of feature flag changes.
|
void addFlagChangeListener(FlagChangeListener listener)
The listener will be notified whenever the SDK receives any change to any feature flag's configuration, or to a user segment that is referenced by a feature flag. If the updated flag is used as a prerequisite for other flags, the SDK assumes that those flags may now behave differently and sends flag change events for them as well.
Note that this does not necessarily mean the flag's value has changed for any particular user, only that
some part of the flag configuration was changed so that it may return a different value than it
previously returned for some user. If you want to track flag value changes, use
addFlagValueChangeListener(String, LDUser, FlagValueChangeListener)
instead.
If using the file data source (FileData
), any change in
a data file will be treated as a change to every flag. Again, use
addFlagValueChangeListener(String, LDUser, FlagValueChangeListener)
(or just re-evaluate the flag
yourself) if you want to know whether this is a change that really affects a flag's value.
Change events only work if the SDK is actually connecting to LaunchDarkly (or using the file data source).
If the SDK is only reading flags from a database (Components.externalUpdatesOnly()
) then it cannot
know when there is a change, because flags are read on an as-needed basis.
The listener will be called from a worker thread.
Calling this method for an already-registered listener has no effect.
listener
- the event listener to registerremoveFlagChangeListener(FlagChangeListener)
,
FlagChangeListener
,
addFlagValueChangeListener(String, LDUser, FlagValueChangeListener)
void removeFlagChangeListener(FlagChangeListener listener)
Calling this method for a listener that was not previously registered has no effect.
listener
- the event listener to unregisteraddFlagChangeListener(FlagChangeListener)
,
addFlagValueChangeListener(String, LDUser, FlagValueChangeListener)
,
FlagChangeListener
FlagChangeListener addFlagValueChangeListener(java.lang.String flagKey, LDUser user, FlagValueChangeListener listener)
When you call this method, it first immediately evaluates the feature flag. It then uses
addFlagChangeListener(FlagChangeListener)
to start listening for feature flag configuration
changes, and whenever the specified feature flag changes, it re-evaluates the flag for the same user.
It then calls your FlagValueChangeListener
if and only if the resulting value has changed.
All feature flag evaluations require an instance of LDUser
. If the feature flag you are
tracking does not have any user targeting rules, you must still pass a dummy user such as
new LDUser("for-global-flags")
. If you do not want the user to appear on your dashboard, use
the anonymous
property: new LDUserBuilder("for-global-flags").anonymous(true).build()
.
The returned FlagChangeListener
represents the subscription that was created by this method
call; to unsubscribe, pass that object (not your FlagValueChangeListener
) to
removeFlagChangeListener(FlagChangeListener)
.
flagKey
- the flag key to be evaluateduser
- the user properties for evaluationlistener
- an object that you provide which will be notified of changesFlagChangeListener
that can be used to unregister the listener