Profiling some time ago showed Object[] allocation as a hot spot.
This change reduce the impact of that hotspot.
The _values will be reused only in the case of the post-back
when restoreState() and saveState() will be called within the same
request.
And yes, if a state manager is used where the tree itself is stored
in the session, there would be higher memory usage.
We were trying to tune for the common case.
Mark Collette wrote:
> Can someone explain something about state saving to me? This is rom
> HtmlColumn:
>
> private Object[] _values;
>
> public Object saveState(FacesContext _context) {
> if (_values == null) {
> _values = new Object[3];
> }
> _values[0] = super.saveState(_context);
> _values[1] = footerClass;
> _values[2] = headerClass;
> return _values;
> }
>
> public void restoreState(FacesContext _context, Object _state) {
> _values = (Object[]) _state;
> super.restoreState(_context, _values[0]);
> this.footerClass = (java.lang.String) _values[1];
> this.headerClass = (java.lang.String) _values[2];
> }
>
>
> Why make _values be an instance field, instead of just allocating it
> on the stack? Won't the component tree be blown away, so that _values
> isn't being reused, anyway? And if the component tree did stick
> around, wouldn't the standing memory requirements go up, with all
> these Object[] sticking around?
>
> - Mark Collette
>
>
>
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