ViewStateManagerImpl (Apache Sling 9 API)

java.lang.Object
- org.apache.sling.discovery.commons.providers.base.ViewStateManagerImpl

All Implemented Interfaces:

ViewStateManager
```
public class ViewStateManagerImpl
extends Object
implements ViewStateManager
```
The ViewStateManager is at the core of managing TopologyEventListeners, the 'view state' (changing vs changed) and sending out the appropriate and according TopologyEvents to the registered listeners.
Note re synchronization: this class rquires a lock object to be passed in the constructor - this will be applied to all public methods appropriately. Additionally, the ClusterSyncService callback will also be locked using the provided lock object.

Field Summary

Fields
Modifier and Type Field and Description

protected java.util.concurrent.locks.Lock lock
The lock object with which all public methods are guarded - to be provided in the constructor.

Fields
Modifier and Type	Field and Description
`protected java.util.concurrent.locks.Lock`	`lock` The lock object with which all public methods are guarded - to be provided in the constructor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`bind(TopologyEventListener eventListener)` Binds the given eventListener, sending it an INIT event if applicable.
`protected boolean`	`hadPreviousView()`
`void`	`handleActivated()` Handles activation - ie marks this manager as activated thus the TOPOLOGY_INIT event can be sent to already bound listeners and subsequent calls to handleChanging/handleNewView will result in according/appropriate TOPOLOGY_CHANGING/ TOPOLOGY_CHANGED events.
`void`	`handleChanging()` Handles the fact that some (possibly early) indicator of a change in a topology has been detected and that a new view is being agreed upon (whatever that means, be it voting or similar).
`void`	`handleDeactivated()` Must be called when the corresponding service (typically a DiscoveryService implementation) is deactivated.
`void`	`handleNewView(BaseTopologyView newView)` Handles the fact that a new view became true/established and sends out TOPOLOGY_INIT to uninitialized listeners and TOPOLOGY_CHANGED to already initialized listeners (in the latter case, also sends a TOPOLOGY_CHANGING if that has not yet been done)
`void`	`installMinEventDelayHandler(DiscoveryService discoveryService, Scheduler scheduler, long minEventDelaySecs)` Installs an optional 'min event delay handler' which, using the given scheduler, delays sending TOPOLOGY_CHANGED event after receiving a handleNewView - with the idea as to limit the number of toggling between view states.
`protected boolean`	`onlyDiffersInProperties(BaseTopologyView newView)`
`boolean`	`unbind(TopologyEventListener eventListener)` Unbinds the given eventListener, returning whether or not it was bound at all.
`protected boolean`	`unchanged(BaseTopologyView newView)`
`int`	`waitForAsyncEvents(long timeout)` for testing only: wait for any potentially queued async events to be delivered before returning.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - lock
```
protected final java.util.concurrent.locks.Lock lock
```
    The lock object with which all public methods are guarded - to be provided in the constructor.
- Method Detail
  - installMinEventDelayHandler
```
public void installMinEventDelayHandler(DiscoveryService discoveryService,
                                        Scheduler scheduler,
                                        long minEventDelaySecs)
```
    Description copied from interface: ViewStateManager
    
    Installs an optional 'min event delay handler' which, using the given scheduler, delays sending TOPOLOGY_CHANGED event after receiving a handleNewView - with the idea as to limit the number of toggling between view states.
    
    Specified by:
    
    installMinEventDelayHandler in interface ViewStateManager
  - hadPreviousView
```
protected boolean hadPreviousView()
```
  - unchanged
```
protected boolean unchanged(BaseTopologyView newView)
```
  - bind
```
public void bind(TopologyEventListener eventListener)
```
    Description copied from interface: ViewStateManager
    
    Binds the given eventListener, sending it an INIT event if applicable.
    
    Specified by:
    
    bind in interface ViewStateManager
    
    Parameters:
    
    eventListener - the eventListener that is to bind
  - unbind
```
public boolean unbind(TopologyEventListener eventListener)
```
    Description copied from interface: ViewStateManager
    
    Unbinds the given eventListener, returning whether or not it was bound at all.
    
    Specified by:
    
    unbind in interface ViewStateManager
    
    Parameters:
    
    eventListener - the eventListner that is to unbind
    
    Returns:
    
    whether or not the listener was added in the first place
  - handleActivated
```
public void handleActivated()
```
    Description copied from interface: ViewStateManager
    
    Handles activation - ie marks this manager as activated thus the TOPOLOGY_INIT event can be sent to already bound listeners and subsequent calls to handleChanging/handleNewView will result in according/appropriate TOPOLOGY_CHANGING/ TOPOLOGY_CHANGED events.
    
    Specified by:
    
    handleActivated in interface ViewStateManager
  - handleDeactivated
```
public void handleDeactivated()
```
    Description copied from interface: ViewStateManager
    
    Must be called when the corresponding service (typically a DiscoveryService implementation) is deactivated.
    Will mark this manager as deactivated and flags the last available view as not current.
    
    Specified by:
    
    handleDeactivated in interface ViewStateManager
  - handleChanging
```
public void handleChanging()
```
    Description copied from interface: ViewStateManager
    
    Handles the fact that some (possibly early) indicator of a change in a topology has been detected and that a new view is being agreed upon (whatever that means, be it voting or similar).
    Will send out TOPOLOGY_CHANGING to all initialized listeners.
    
    Specified by:
    
    handleChanging in interface ViewStateManager
  - handleNewView
```
public void handleNewView(BaseTopologyView newView)
```
    Description copied from interface: ViewStateManager
    
    Handles the fact that a new view became true/established and sends out TOPOLOGY_INIT to uninitialized listeners and TOPOLOGY_CHANGED to already initialized listeners (in the latter case, also sends a TOPOLOGY_CHANGING if that has not yet been done)
    
    Specified by:
    
    handleNewView in interface ViewStateManager
    
    Parameters:
    
    newView - the new, established view true if we were either in changing mode or the newView was different from the previous one.
  - onlyDiffersInProperties
```
protected boolean onlyDiffersInProperties(BaseTopologyView newView)
```
  - waitForAsyncEvents
```
public int waitForAsyncEvents(long timeout)
```
    Description copied from interface: ViewStateManager
    
    for testing only: wait for any potentially queued async events to be delivered before returning.
    
    Specified by:
    
    waitForAsyncEvents in interface ViewStateManager
    
    Parameters:
    
    timeout - time in millis to wait for at max - 0 to not wait at all - -1 to wait indefinitely
    
    Returns:
    
    0 if no more async events exist, or the number of queued or in-flight (being sent) events if the timeout hit early

Class ViewStateManagerImpl

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

lock

Method Detail

installMinEventDelayHandler

hadPreviousView

unchanged

bind

unbind

handleActivated

handleDeactivated

handleChanging

handleNewView

onlyDiffersInProperties

waitForAsyncEvents