15.1 The ViewHandler Class

The javax.faces.application.ViewHandler class is responsible for making JSF views available to the rest of the JSF framework. It's a fairly simple class, with three primary methods: createView(), renderView(), and restoreView( ).

The createView() method creates a component tree corresponding to a view identifier with at least a UIViewRoot component as the root, and returns it initialized with render kit and locale information. The renderView() method renders the specified view and saves the view state, and the restoreView() method restores a view from the saved state information. Both of these methods cooperate with a javax.faces.application.StateManager for handling the details about how and where the view state is saved. A custom ViewHandler can support pretty much any type of view representation by implementing these three methods.

Declare that an application uses a custom ViewHandler in the faces-config.xml file:

<faces-config>

  ...

  <application>

    <view-handler>

      com.mycompany.jsf.pl.ClassViewHandlerImpl

    </view-handler>

  </application>

  ...

</faces-config>

Because only one ViewHandler can be used at a time, I have commented out the declarations for the custom handlers we develop in this chapter in the book examples faces-config.xml file. To run the examples from this chapter, you must first remove the comments around one declaration at a time and restart the web container.