The ActionLink, DirectLink and Form components (which make use of the action and direct services) inform the application when they have been triggered using listeners.

A listener is an object that implements the IActionListener interface.

public void actionTriggered(IComponent component, IRequestCycle cycle)
  throws RequestCycleException;

Prior to release 1.0.2, it was necessary to create an object to be notified by the component; this was almost always an annonymous inner class:

public IActionListener getFormListener()
{
  return new IActionListener()
  {
    public void actionTriggered(IComponent component, IRequestCycle cycle)
      throws RequestCycleException
    {
      // perform some operation ...
    }
  };
}

Although elegant in theory, that's simply too much Java code for too little effect. Starting with Tapestry 1.0.2, it is possible to create a listener method instead.

A listener method takes the form:

public void method-name(IRequestCycle cycle)
throws RequestCycleException;

	Note
	The throws clause is optional and may be omitted. However, no other exception may be thrown.

In reality, listener objects have not gone away. Instead, there's a mechanism whereby a listener object is created automatically when needed. Each component includes a property, listeners, that is a collection of listener objects for the component, synthesized from the available public methods. The listener objects are properties, with the names corresponding to the method names.

	Tip
	The class AbstractEngine (the base class for SimpleEngine) also implements a listeners property. This allows you to easily add listener methods to your application engine.

The earlier example is much simpler:

public void formSubmit(IRequestCycle cycle)
{
  // perform some operation ...
}

However, the property path for the listener binding must be changed, from formListener to listeners.formSubmit.