PersistedHippoEventListener (Repository API 15.2.0 API)

```
public interface PersistedHippoEventListener
```
Developers can implement this interface to asynchronously receive HippoEvents after they occurred in the repository, across a repository cluster.
Such a listener must be registered through the PersistedHippoEventListenerRegistry, like for example:
```
   
       PersistedHippoEventListenerRegistry.get().register(myPersistedHippoEventListener);
   
   
```
A PersistedHippoEventListener must provide a (cluster node instance unique) channel name which will be used to track which persisted events already have been delivered to the listener.

A listener will get a consistent and ordered delivery of all events within a specific getEventCategory() (or all if unspecified) through that channel, but such events will only be delivered once (within one cluster node) through that channel.
Therefore there should only be one listener (registered) per channel per cluster node.
If more than one listener is registered on one channel, only one will get the events delivered!

A listener also has to define through onlyNewEvents() if it should receive persisted events even from before the first time registration on its channel (for as much is looked back in time, depending on the service configuration), or only events after the first time channel registration will be delivered.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`String`	`getChannelName()`
`String`	`getEventCategory()`
`void`	`onHippoEvent(HippoEvent event)`	Persisted HippoEvents will be delivered through this method.
`boolean`	`onlyNewEvents()`

- Method Detail
  - getEventCategory
```
String getEventCategory()
```
    Returns:
    
    which category of events this listener is interested in, or null to indicate all events.
  - getChannelName
```
String getChannelName()
```
    Returns:
    
    The cluster node unique channel name to listen on for events. Note: must conform to JCR node name restrictions.
  - onlyNewEvents
```
boolean onlyNewEvents()
```
    Returns:
    
    if true, only events persisted after the first time registration on this getChannelName() will be delivered.
  - onHippoEvent
```
void onHippoEvent(HippoEvent event)
```
    Persisted HippoEvents will be delivered through this method.
    
    Parameters:
    
    event - the event