javax.faces.component
Class _DeltaStateHelper

java.lang.Object
  javax.faces.component._DeltaStateHelper

All Implemented Interfaces:

StateHelper, StateHolder

public class _DeltaStateHelper
extends java.lang.Object
implements StateHelper

A delta enabled state holder implementing the StateHolder Interface.

Components implementing the PartalStateHolder interface have an initial state and delta states, the initial state is the one holding all root values and deltas store differences to the initial states

For components not implementing partial state saving only the initial states are of importance, everything is stored and restored continously there

The state helper seems to have three internal storage mechanisms: one being a list which stores plain values, one being a key value pair which stores key values in maps add serves the plain list type while put serves the key value type, the third is the value which has to be stored plainly as is!

In other words, this map can be seen as a composite map. It has two maps: initial state map and delta map.

If delta map is used (method component.initialStateMarked() ), base or initial state map cannot be changed, since all changes should be tracked on delta map.

The intention of this class is just hold property values and do a clean separation between initial state and delta.

The code from this class comes from a refactor of org.apache.myfaces.trinidad.bean.util.PropertyHashMap

The context from this class comes and that should be taken into account is this:

First request:

• A new template is created (using javax.faces.view.ViewDeclarationLanguage.buildView method) and component.markInitialState is called from its related TagHandler classes (see javax.faces.view.facelets.ComponentHandler ). When this method is executed, the component tree was populated from the values set in the facelet abstract syntax tree (or in other words composition of facelets templates).
• From this point all updates on the variables are considered "delta".
• SaveState, if initialStateMarked is true, only delta is saved.

Second request (and next ones)

• A new template is created and component.markInitialState is called from its related TagHandler classes again. In this way, components like c:forEach or c:if, that add or remove components could notify about this and handle them properly (see javax.faces.view.StateManagementStrategy). Note that a component restored using this method is no different as the same component at the first request at the same time.
• A call for restoreState is done, passing the delta as object value. If no delta, the state is complete and no call is triggered.
• Lifecycle occur, changing the necessary stuff.
• SaveState, if initialStateMarked is true, only delta is saved.

From the previous analysis, the following conclusions arise:

• This class only needs to keep track of delta changes, so when restoreState/saveState is called, the right objects are passed.
• UIComponent.clearInitialState is used to reset the partial state holder to a non delta state, so the state to be saved by saveState is no longer a delta instead is a full state. If a call to clearInitialState occur it is not expected a call for UIComponent.markInitialState occur on the current request.
• The state is handled in the same way on UIData, so components inside UIData share its state on all rows. There is no way to save delta per row.
• The map backed by method put(Serializable,String,Object) is a replacement of UIComponentBase.attributesMap and UIComponent.bindings map. Note that on jsf 1.2, instances saved on attributesMap should not be StateHolder, but on jsf 2.0 it is possible to have it. PartialStateHolder instances are not handled in this map, or in other words delta state is not handled in this classes (markInitialState and clearInitialState is not propagated).
• The list backed by method add(Serializable,Object) should be (is not) a replacement of UIComponentBase.facesListeners, but note that StateHelper does not implement PartialStateHolder, and facesListener could have instances of that class that needs to be notified when UIComponent.markInitialState or UIComponent.clearInitialState is called, or in other words facesListeners should deal with PartialStateHolder instances.
• The list backed by method add(Serializable,Object) is a replacement of UIViewRoot.phaseListeners list. Note that instances of PhaseListener are not expected to implement StateHolder or PartialStateHolder.

NOTE: The current implementation of StateHelper on RI does not handle stateHolder values internally. To prevent problems when developers create custom components we should do this too. But anyway, the code that handle this case should be let here as comment, if some day this feature is provided. Note than stateHolder aware properties like converter, validator or listeners should deal with StateHolder or PartialStateHolder on component classes.

Version:

$Rev: 788877 $ $Date: 2009-06-26 16:30:38 -0500 (Fri, 26 Jun 2009) $

Author:

Werner Punz, Leonardo Uribe (latest modification by $Author: lu4242 $)

Constructor Summary

_DeltaStateHelper(UIComponent component)

Method Summary

void	add(java.io.Serializable key, java.lang.Object value)
java.lang.Object	eval(java.io.Serializable key)
java.lang.Object	eval(java.io.Serializable key, java.lang.Object defaultValue)
java.lang.Object	get(java.io.Serializable key)
protected boolean	isInitialStateMarked()
boolean	isTransient()
java.lang.Object	put(java.io.Serializable key, java.lang.Object value)
java.lang.Object	put(java.io.Serializable key, java.lang.String mapKey, java.lang.Object value)
java.lang.Object	remove(java.io.Serializable key)
java.lang.Object	remove(java.io.Serializable key, java.lang.Object valueOrKey)
void	restoreState(FacesContext context, java.lang.Object state)
java.lang.Object	saveState(FacesContext context) Serializing cod the serialized data structure consists of key value pairs unless the value itself is an internal array or a map in case of an internal array or map the value itself is another array with its initial value myfaces.InternalArray, myfaces.internalMap the internal Array is then mapped to another array the internal Map again is then mapped to a map with key value pairs
void	setTransient(boolean transientValue)

Methods inherited from class java.lang.Object

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

Constructor Detail

_DeltaStateHelper

public _DeltaStateHelper(UIComponent component)

Method Detail

isInitialStateMarked

protected boolean isInitialStateMarked()

add

public void add(java.io.Serializable key,
                java.lang.Object value)

Specified by:

add in interface StateHelper

eval

public java.lang.Object eval(java.io.Serializable key)

Specified by:

eval in interface StateHelper

eval

public java.lang.Object eval(java.io.Serializable key,
                             java.lang.Object defaultValue)

Specified by:

eval in interface StateHelper

get

public java.lang.Object get(java.io.Serializable key)

Specified by:

get in interface StateHelper

put

public java.lang.Object put(java.io.Serializable key,
                            java.lang.Object value)

Specified by:

put in interface StateHelper

put

public java.lang.Object put(java.io.Serializable key,
                            java.lang.String mapKey,
                            java.lang.Object value)

Specified by:

put in interface StateHelper

remove

public java.lang.Object remove(java.io.Serializable key)

Specified by:

remove in interface StateHelper

remove

public java.lang.Object remove(java.io.Serializable key,
                               java.lang.Object valueOrKey)

Specified by:

remove in interface StateHelper

isTransient

public boolean isTransient()

Specified by:

isTransient in interface StateHolder

saveState

public java.lang.Object saveState(FacesContext context)

Serializing cod the serialized data structure consists of key value pairs unless the value itself is an internal array or a map in case of an internal array or map the value itself is another array with its initial value myfaces.InternalArray, myfaces.internalMap the internal Array is then mapped to another array the internal Map again is then mapped to a map with key value pairs

Specified by:

saveState in interface StateHolder

restoreState

public void restoreState(FacesContext context,
                         java.lang.Object state)

Specified by:

restoreState in interface StateHolder

setTransient

public void setTransient(boolean transientValue)

Specified by:

setTransient in interface StateHolder