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## org.apache.cayenne.event
Interface EventManager

All Known Implementing Classes:
  DefaultEventManager

    public interface EventManager

This class acts as bridge between an Object that wants to inform others about its current state or a change thereof (Publisher) and a list of objects interested in the Subject (Listeners).

Since:
  3.1 before 3.1 this was a concrete class.

Method Summary
`void` | `addListener(Object listener, String methodName, Class<?> eventParameterClass, EventSubject subject)` Register an `EventListener` for events sent by any sender.
`void` | `addListener(Object listener, String methodName, Class<?> eventParameterClass, EventSubject subject, Object sender)` Register an `EventListener` for events sent by a specific sender.
`void` | `addNonBlockingListener(Object listener, String methodName, Class<?> eventParameterClass, EventSubject subject)`
`void` | `addNonBlockingListener(Object listener, String methodName, Class<?> eventParameterClass, EventSubject subject, Object sender)`
`boolean` | `isSingleThreaded()` Returns true if this EventManager is single-threaded.
`void` | `postEvent(EventObject event, EventSubject subject)` Sends an event to all registered objects about a particular subject.
`void` | `postNonBlockingEvent(EventObject event, EventSubject subject)` Sends an event to all registered objects about a particular subject.
`boolean` | `removeAllListeners(EventSubject subject)` Removes all listeners for a given subject.
`boolean` | `removeListener(Object listener)` Unregister the specified listener from all event subjects handled by this manager instance.
`boolean` | `removeListener(Object listener, EventSubject subject)` Unregister the specified listener for the events about the given subject.
`boolean` | `removeListener(Object listener, EventSubject subject, Object sender)` Unregister the specified listener for the events about the given subject and the given sender.

Method Detail

### isSingleThreaded

    boolean isSingleThreaded()

  Returns true if this EventManager is single-threaded. If so it will throw an exception on any attempt to register an unblocking listener or dispatch a non-blocking event.

  Since:
    1.2

### addListener

    void addListener(Object listener,
                     String methodName,
                     Class<?> eventParameterClass,
                     EventSubject subject)

  Register an `EventListener` for events sent by any sender.

  Throws:
    `RuntimeException` - if `methodName` is not found.

### addNonBlockingListener

    void addNonBlockingListener(Object listener,
                                String methodName,
                                Class<?> eventParameterClass,
                                EventSubject subject)

### addListener

    void addListener(Object listener,
                     String methodName,
                     Class<?> eventParameterClass,
                     EventSubject subject,
                     Object sender)

  Register an `EventListener` for events sent by a specific sender.

  Parameters:
    `listener` - the object to be notified about events
    `methodName` - the name of the listener method to be invoked
    `eventParameterClass` - the class of the single event argument passed to `methodName`
    `subject` - the event subject that the listener is interested in
    `sender` - the object whose events the listener is interested in; `null` means 'any sender'.
  Throws:
    `RuntimeException` - if `methodName` is not found

### addNonBlockingListener

    void addNonBlockingListener(Object listener,
                                String methodName,
                                Class<?> eventParameterClass,
                                EventSubject subject,
                                Object sender)

### removeListener

    boolean removeListener(Object listener)

  Unregister the specified listener from all event subjects handled by this manager instance.

  Parameters:
    `listener` - the object to be unregistered
  Returns:
    `true` if `listener` could be removed for any existing subjects, else returns `false`.

### removeAllListeners

    boolean removeAllListeners(EventSubject subject)

  Removes all listeners for a given subject.

### removeListener

    boolean removeListener(Object listener,
                           EventSubject subject)

  Unregister the specified listener for the events about the given subject.

  Parameters:
    `listener` - the object to be unregistered
    `subject` - the subject from which the listener is to be unregistered
  Returns:
    `true` if `listener` could be removed for the given subject, else returns `false`.

### removeListener

    boolean removeListener(Object listener,
                           EventSubject subject,
                           Object sender)

  Unregister the specified listener for the events about the given subject and the given sender.

  Parameters:
    `listener` - the object to be unregistered
    `subject` - the subject from which the listener is to be unregistered
    `sender` - the object whose events the listener was interested in; `null` means 'any sender'.
  Returns:
    `true` if `listener` could be removed for the given subject, else returns `false`.

### postEvent

    void postEvent(EventObject event,
                   EventSubject subject)

  Sends an event to all registered objects about a particular subject. Event is sent synchronously, so the sender thread is blocked until all the listeners finish processing the event.

  Parameters:
    `event` - the event to be posted to the observers
    `subject` - the subject about which observers will be notified
  Throws:
    `IllegalArgumentException` - if event or subject are null

### postNonBlockingEvent

    void postNonBlockingEvent(EventObject event,
                              EventSubject subject)

  Sends an event to all registered objects about a particular subject. Event is queued by EventManager, releasing the sender thread, and is later dispatched in a separate thread.

  Parameters:
    `event` - the event to be posted to the observers
    `subject` - the subject about which observers will be notified
  Throws:
    `IllegalArgumentException` - if event or subject are null
  Since:
    1.1

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