Module org.omnifaces

Package org.omnifaces.taghandler

Class EnableRestorableView

java.lang.Object

jakarta.faces.view.facelets.TagHandler

org.omnifaces.taghandler.EnableRestorableView

All Implemented Interfaces:

FaceletHandler

public class EnableRestorableView
extends TagHandler

The <o:enableRestorableView> taghandler instructs the view handler to recreate the entire view whenever the view has been expired, i.e. whenever ViewHandler.restoreView(FacesContext, String) returns null and the current request is a postback. This effectively prevents ViewExpiredException on the view. This tag needs to be placed in <f:metadata> of the view.

There are however technical design limitations: the recreated view is exactly the same as during the initial request. In other words, the view has lost its state. Any modifications which were made after the original initial request, either by taghandlers or (ajax) conditionally rendered components based on some view or even session scoped variables, are completely lost. Thus, the view should be designed that way that it can be used with a request scoped bean. You can use it with a view scoped bean, but then you should add a @PostConstruct which checks if the request is a postback and then fill the missing bean properties based on request parameters.

Usage

To enable the restorable view, just add the <enableRestorableView> to the view metadata.

 <f:metadata>
     <o:enableRestorableView/>
 </f:metadata>
 

Mojarra's new stateless mode

Since Mojarra 2.1.19, about 2 months after OmniFaces introduced the <o:enableRestorableView>, it's possible to enable a stateless mode on the view by simply setting its transient attribute to true:

 <f:view transient="true">
     ...
 </f:view>
 

This goes actually a step further than <o:enableRestorableView> as no state would be saved at all. However, on those kind of pages where <o:enableRestorableView> would work just fine, this statelessness should not form any problem at all. So, if you have at least Mojarra 2.1.19 at hands, use the transient="true" instead.

Since:

1.3

Author:

Bauke Scholtz

See Also:

OmniViewHandler

Field Summary

Fields inherited from class jakarta.faces.view.facelets.TagHandler

nextHandler, tag, tagId

Constructor Summary

Constructors

Constructor	Description
EnableRestorableView(TagConfig config)	The tag constructor.

Method Summary

Modifier and Type	Method	Description
void	apply(FaceletContext context, UIComponent parent)	Enable the current view to be restorable.
static boolean	isRestorableView(UIViewRoot view)	Returns true if given view indeed contains EnableRestorableView.
static boolean	isRestorableViewRequest(FacesContext context, UIViewRoot view)	Returns true if given view is null, and this is a postback, and EnableRestorableView has been activated.

Methods inherited from class jakarta.faces.view.facelets.TagHandler

getAttribute, getRequiredAttribute, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

EnableRestorableView

public EnableRestorableView(TagConfig config)

The tag constructor.

Parameters:

config - The tag config.

Method Detail

apply

public void apply(FaceletContext context,
                  UIComponent parent)
           throws IOException

Enable the current view to be restorable. This basically sets a specific view attribute which the OmniViewHandler could intercept on.

Throws:

IllegalStateException - When given parent is not an instance of UIViewRoot.

IOException

isRestorableViewRequest

public static boolean isRestorableViewRequest(FacesContext context,
                                              UIViewRoot view)

Returns true if given view is null, and this is a postback, and EnableRestorableView has been activated.

Parameters:

context - The involved faces context.

view - The involved view.

Returns:

true if given view is null, and this is a postback, and EnableRestorableView has been activated.

isRestorableView

public static boolean isRestorableView(UIViewRoot view)

Returns true if given view indeed contains EnableRestorableView.

Parameters:

view - The involved view.

Returns:

true if given view indeed contains EnableRestorableView.