EventSource

java.lang.Object
- org.apache.commons.configuration.event.EventSource

Direct Known Subclasses:

AbstractConfiguration
```
public class EventSource
extends java.lang.Object
```
A base class for objects that can generate configuration events.

This class implements functionality for managing a set of event listeners that can be notified when an event occurs. It can be extended by configuration classes that support the event mechanism. In this case these classes only need to call the fireEvent() method when an event is to be delivered to the registered listeners.

Adding and removing event listeners can happen concurrently to manipulations on a configuration that cause events. The operations are synchronized.

With the detailEvents property the number of detail events can be controlled. Some methods in configuration classes are implemented in a way that they call other methods that can generate their own events. One example is the setProperty() method that can be implemented as a combination of clearProperty() and addProperty(). With detailEvents set to true, all involved methods will generate events (i.e. listeners will receive property set events, property clear events, and property add events). If this mode is turned off (which is the default), detail events are suppressed, so only property set events will be received. Note that the number of received detail events may differ for different configuration implementations. HierarchicalConfiguration for instance has a custom implementation of setProperty(), which does not generate any detail events.

In addition to "normal" events, error events are supported. Such events signal an internal problem that occurred during access of properties. For them a special listener interface exists: ConfigurationErrorListener. There is another set of methods dealing with event listeners of this type. The fireError() method can be used by derived classes to send notifications about errors to registered observers.

Since:

1.3

Version:

$Id: EventSource.java 1234617 2012-01-22 21:31:01Z oheger $

Author:

Commons Configuration team

Constructor Summary

Constructors
Constructor and Description

EventSource()
Creates a new instance of EventSource.

Constructors
Constructor and Description
`EventSource()` Creates a new instance of `EventSource`.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`addConfigurationListener(ConfigurationListener l)` Adds a configuration listener to this object.
`void`	`addErrorListener(ConfigurationErrorListener l)` Adds a new configuration error listener to this object.
`void`	`clearConfigurationListeners()` Removes all registered configuration listeners.
`void`	`clearErrorListeners()` Removes all registered error listeners.
`protected java.lang.Object`	`clone()` Overrides the `clone()` method to correctly handle so far registered event listeners.
`protected ConfigurationErrorEvent`	`createErrorEvent(int type, java.lang.String propName, java.lang.Object propValue, java.lang.Throwable ex)` Creates a `ConfigurationErrorEvent` object based on the passed in parameters.
`protected ConfigurationEvent`	`createEvent(int type, java.lang.String propName, java.lang.Object propValue, boolean before)` Creates a `ConfigurationEvent` object based on the passed in parameters.
`protected void`	`fireError(int type, java.lang.String propName, java.lang.Object propValue, java.lang.Throwable ex)` Creates an error event object and delivers it to all registered error listeners.
`protected void`	`fireEvent(int type, java.lang.String propName, java.lang.Object propValue, boolean before)` Creates an event object and delivers it to all registered event listeners.
`java.util.Collection<ConfigurationListener>`	`getConfigurationListeners()` Returns a collection with all configuration event listeners that are currently registered at this object.
`java.util.Collection<ConfigurationErrorListener>`	`getErrorListeners()` Returns a collection with all configuration error listeners that are currently registered at this object.
`boolean`	`isDetailEvents()` Returns a flag whether detail events are enabled.
`boolean`	`removeConfigurationListener(ConfigurationListener l)` Removes the specified event listener so that it does not receive any further events caused by this object.
`boolean`	`removeErrorListener(ConfigurationErrorListener l)` Removes the specified error listener so that it does not receive any further events caused by this object.
`void`	`setDetailEvents(boolean enable)` Determines whether detail events should be generated.

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

- Constructor Detail
  - EventSource
```
public EventSource()
```
    Creates a new instance of EventSource.
- Method Detail
  - addConfigurationListener
```
public void addConfigurationListener(ConfigurationListener l)
```
    Adds a configuration listener to this object.
    
    Parameters:
    
    l - the listener to add
  - removeConfigurationListener
```
public boolean removeConfigurationListener(ConfigurationListener l)
```
    Removes the specified event listener so that it does not receive any further events caused by this object.
    
    Parameters:
    
    l - the listener to be removed
    
    Returns:
    
    a flag whether the event listener was found
  - getConfigurationListeners
```
public java.util.Collection<ConfigurationListener> getConfigurationListeners()
```
    Returns a collection with all configuration event listeners that are currently registered at this object.
    
    Returns:
    
    a collection with the registered ConfigurationListeners (this collection is a snapshot of the currently registered listeners; manipulating it has no effect on this event source object)
  - clearConfigurationListeners
```
public void clearConfigurationListeners()
```
    Removes all registered configuration listeners.
  - isDetailEvents
```
public boolean isDetailEvents()
```
    Returns a flag whether detail events are enabled.
    
    Returns:
    
    a flag if detail events are generated
  - setDetailEvents
```
public void setDetailEvents(boolean enable)
```
    Determines whether detail events should be generated. If enabled, some methods can generate multiple update events. Note that this method records the number of calls, i.e. if for instance setDetailEvents(false) was called three times, you will have to invoke the method as often to enable the details.
    
    Parameters:
    
    enable - a flag if detail events should be enabled or disabled
  - addErrorListener
```
public void addErrorListener(ConfigurationErrorListener l)
```
    Adds a new configuration error listener to this object. This listener will then be notified about internal problems.
    
    Parameters:
    
    l - the listener to register (must not be null)
    
    Since:
    
    1.4
  - removeErrorListener
```
public boolean removeErrorListener(ConfigurationErrorListener l)
```
    Removes the specified error listener so that it does not receive any further events caused by this object.
    
    Parameters:
    
    l - the listener to remove
    
    Returns:
    
    a flag whether the listener could be found and removed
    
    Since:
    
    1.4
  - clearErrorListeners
```
public void clearErrorListeners()
```
    Removes all registered error listeners.
    
    Since:
    
    1.4
  - getErrorListeners
```
public java.util.Collection<ConfigurationErrorListener> getErrorListeners()
```
    Returns a collection with all configuration error listeners that are currently registered at this object.
    
    Returns:
    
    a collection with the registered ConfigurationErrorListeners (this collection is a snapshot of the currently registered listeners; it cannot be manipulated)
    
    Since:
    
    1.4
  - fireEvent
```
protected void fireEvent(int type,
                         java.lang.String propName,
                         java.lang.Object propValue,
                         boolean before)
```
    Creates an event object and delivers it to all registered event listeners. The method will check first if sending an event is allowed (making use of the detailEvents property), and if listeners are registered.
    
    Parameters:
    
    type - the event's type
    
    propName - the name of the affected property (can be null)
    
    propValue - the value of the affected property (can be null)
    
    before - the before update flag
  - createEvent
```
protected ConfigurationEvent createEvent(int type,
                                         java.lang.String propName,
                                         java.lang.Object propValue,
                                         boolean before)
```
    Creates a ConfigurationEvent object based on the passed in parameters. This is called by fireEvent() if it decides that an event needs to be generated.
    
    Parameters:
    
    type - the event's type
    
    propName - the name of the affected property (can be null)
    
    propValue - the value of the affected property (can be null)
    
    before - the before update flag
    
    Returns:
    
    the newly created event object
  - fireError
```
protected void fireError(int type,
                         java.lang.String propName,
                         java.lang.Object propValue,
                         java.lang.Throwable ex)
```
    Creates an error event object and delivers it to all registered error listeners.
    
    Parameters:
    
    type - the event's type
    
    propName - the name of the affected property (can be null)
    
    propValue - the value of the affected property (can be null)
    
    ex - the Throwable object that caused this error event
    
    Since:
    
    1.4
  - createErrorEvent
```
protected ConfigurationErrorEvent createErrorEvent(int type,
                                                   java.lang.String propName,
                                                   java.lang.Object propValue,
                                                   java.lang.Throwable ex)
```
    Creates a ConfigurationErrorEvent object based on the passed in parameters. This is called by fireError() if it decides that an event needs to be generated.
    
    Parameters:
    
    type - the event's type
    
    propName - the name of the affected property (can be null)
    
    propValue - the value of the affected property (can be null)
    
    ex - the Throwable object that caused this error event
    
    Returns:
    
    the event object
    
    Since:
    
    1.4
  - clone
```
protected java.lang.Object clone()
                          throws java.lang.CloneNotSupportedException
```
    Overrides the clone() method to correctly handle so far registered event listeners. This implementation ensures that the clone will have empty event listener lists, i.e. the listeners registered at an EventSource object will not be copied.
    
    Overrides:
    
    clone in class java.lang.Object
    
    Returns:
    
    the cloned object
    
    Throws:
    
    java.lang.CloneNotSupportedException - if cloning is not allowed
    
    Since:
    
    1.4

Class EventSource

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

EventSource

Method Detail

addConfigurationListener

removeConfigurationListener

getConfigurationListeners

clearConfigurationListeners

isDetailEvents

setDetailEvents

addErrorListener

removeErrorListener

clearErrorListeners

getErrorListeners

fireEvent

createEvent

fireError

createErrorEvent

clone