Framework Services

This section describes the framework services that are available for views.

ViewContext

The view server-side resources have access to a ViewContext object. The view context provides information about the current authenticated user, the view definition, the instance configuration properties, instance data and the view controller.

  /**
   * The view context.
   */
  @Inject
  ViewContext context;

Instance Data

The view framework exposes a way to store key/value pair "instance data". This data is scoped to a given view instance and user. Instance data is meant to be used for information such as "user prefs" or other lightweight information that supports the experience of your view application. You can access the instance data get and put methods from the ViewContext object.

/**
 * Context object available to the view components to provide access to
 * the view and instance attributes as well as run time information about
 * the current execution context.
 */
public interface ViewContext {

 /**
   * Save an instance data value for the given key.
   *
   * @param key    the key
   * @param value  the value
   *
   * @throws IllegalStateException if no instance is associated
   */
  public void putInstanceData(String key, String value);
  /**
   * Get the instance data value for the given key.
   *
   * @param key  the key
   *
   * @return the instance data value; null if no instance is associated
   */
  public String getInstanceData(String key);

}

Events

Events are an important component of the views framework. Events allow the view to interact with the framework on lifecycle changes (i.e. "framework events"). such as deploy, create and destroy. As well, once a user has collection of views available, eventing allows the views to communicate with other views (i.e. "view events").

Framework Events

To register to receive framework events, in the view.xml, specify a <view-class>this.is.my.view-clazz</view-class> which is a class that implements the View interface.

View Events

From the view context, you can obtain the ViewController object that allows you to register listeners for view events and to fire events for other listeners.

ViewController viewContext.getViewController();

Registering Listeners

A view can register to listen for view events from other views by view name, or by view name + version. When an event is fired from the source view, all registered listeners will receive the event.

https://github.com/apache/ambari/blob/trunk/ambari-views/src/main/java/org/apache/ambari/view/events/Listener.java

Firing Events

1. Create an event.
   http://github.com/apache/ambari/blob/trunk/ambari-views/src/main/java/org/apache/ambari/view/events/Event.java
   
   
2. Fire the event.
   controller.fireEvent(event)

Receiving Events

The framework will notify all registered listeners.

listener.notify(event)