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https://issues.apache.org/jira/browse/TRINIDAD-2091?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13029450#comment-13029450
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Gabrielle Crawford commented on TRINIDAD-2091:
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After thinking about this some more, a property may technically be mutable, for
example it's a String array, but it really shouldn't be considered mutable for
partial state saving because it's never mutated and so we are saving state that
we don't want to save. To give us a little more control over how likely we
think a property is to be mutated, we will add an enumeration to PropertyKey
instead of a boolean capability. For partial state saving we will save anything
marked as SOMETIMES or OFTEN, but won't save things marked as IMMUTABLE or
RARELY. If needed we can later add a context param to control the level. The
enum would look like
public enum Mutable {
IMMUTABLE,
RARELY,
SOMETIMES,
OFTEN
};
> add mutable information to property key to support partial state saving
> -----------------------------------------------------------------------
>
> Key: TRINIDAD-2091
> URL: https://issues.apache.org/jira/browse/TRINIDAD-2091
> Project: MyFaces Trinidad
> Issue Type: Improvement
> Components: Components, Facelets
> Reporter: Gabrielle Crawford
> Assignee: Gabrielle Crawford
> Attachments: trin2091.patch, trin2091v2.patch
>
>
> Mutable attributes are not state saved when using partial state saving. Let's
> start with partial state saving basics
> How does full state saving work? Two things are saved,
> 1. the structure of the component tree - as in parent/child/facet
> relationships
> 2. the state of the components - there is a state object for each
> component, this object might hold all the attribute values.
> Partial state saving is based on the fact that Facelets tag handlers can be
> re-executed during restore view in order to re-create the initial state of
> the component tree so that the structure of the component tree does not need
> to be state saved. Note that this means the tags are now executed during
> restore view, which does not happen in full state saving.
> Because the tags are re-executed with partial state saving, only attribute
> changes made after the tags have been executed need to be state saved. This
> is accomplished by calling markInitialState on the components after the tags
> have been executed, so that only changes applied after markInitialState has
> been called are state saved.
> What is actually saved in partial state saving? The differences for partial
> state saving are:
> 1. the structure of the page - not saved, the tags are re-executed to
> create the structure
> 2. the state of the page - still a tree of state objects, but the state
> object is only a map of the deltas and is therefore usually empty.
> Now let's look at the mutable attribute case. The mutable attribute case is a
> case where the app dev is getting a local attribute off the component and
> mutating it, for example get a local value of a date and mutate it (mutable
> attributes are a fairly rare case, because normally attributes are either EL
> bound or immutable (boolan, string, etc)). In partial state saving only the
> deltas are saved, and deltas are generated by sets on component attributes,
> without a set getting called an attribute will not be in the delta list, and
> therefore won't be state saved, so if an attribute is mutated from outside
> the component the changes would not be state saved.
> Proposal to fix this is only do partial state saving on attributes that tell
> us the type is immutable, since most attributes are String, booleans, and
> other immutable types this means most attributes are still doing partial
> state saving.
> 1 enhance org.apache.myfaces.trinidad.bean.PropertyKey api to add a new
> capability that indicates that the attribute is mutable, defaults to false.
> There would be a new constant CAP_MUTABLE, and a new method isMutable().
> 2. enhance metadata in build files to set this on the applicable property
> keys, add <mfp:mutable>true</mfp:mutable> under <property-extension>
> 3. enhance build tool to look for the metadata and create the appropriate
> capability
> 4. when state saving in
> org.apache.myfaces.trinidad.bean.util.PropertyHashMap.saveState() go through
> the keys and check the propertyKey for CAP_MUTABLE, if it's mutable put the
> value in the deltas map
> New API: Enhance org.apache.myfaces.trinidad.bean.PropertyKey api to add a
> new capability that indicates that the attribute is mutable, defaults to
> false. Add
> 1. new constant CAP_MUTABLE
> 2. new method isMutable().
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