Matthias Wessendorf said the following On 1/5/2010 10:49 AM PT:
On Thu, Dec 31, 2009 at 11:12 PM, Blake Sullivan
<[email protected]> wrote:
UIComponent.getId() is by far the most requested component attribute. There
are a number of reasons for this:
1) The JSF RI has an issue in the JSP-JSF integration which causes getId()
to be called n^2 times where n is the number of children a component has
I guess this is true for MyFaces as well, right?
I'd have to look at the code. There is a trivial change that the RI
could make that would make this o(n) in the common case. The trick is
that the matching code shouldn't start over at index 0 each time. It
should start looking at (last index found) + 1 and wrap around if it
can't find a match. In the common case where the same set of children
exist in the same order between the current saved state and the tags,
this would be o(n).
-- Blake
2) getClientId() calls getId()
3) FindComponent calls getId()
4) The tree visiting code trades off calls to getClientId() for calls to
getId()
FacesBean optimizes attribute Map access at the expense of access directly
through the component. The the extent that Renderers are Components are
accessing the attributes through the attribute Map, this is fine, however
even the Renderers access attributes common to all UIComponents such as id()
through the component directly. Considering the huge number of times that
the the id is accessed (for some renders, this was 8% of the rendering
time), it makes sense to optimize this path.
The proposal is to:
1) Store the id an an instance variable on the UIXComponent
2) Add a new capability flag to PropertyKey indicating that the property is
actually stored elsewhere using a ValueExpression will be stored as the
property's value in the PropertyMap. For access through the FacesBean, the
ValueExpression will be evaluated to get/set the actual value
3) For state saving the ValueExpression is used to retrieve the actual value
and for state restoration the ValueExpression (which has been rebootstrapped
by the UIXComponent) is used to write the value back
4) Instead of setting the id attribute in the FacesBean, UIXComponent stores
it locally and sets an ValueExpression implementation into the FacesBean
that retrieves the value from the UIXComponent
+1 on api/patch
API Changes:
PropertyKey:
add
/**
* Capability indicating that values for this property should be
* be stored and retrieved through a ValueExpression rather than on the
* FacesBean itself
*/
static public final int CAP_VALUE_EXPRESSION_IMPLEMENTATION = 16;
/**
* Returns <code>true</code> if property values for this key are set and get
* using a ValueExpression rather than storing the value in the FacesBean.
* @return <code>true</code> if properties values for this key are retrieved
* with a ValueExpression.
*/
public boolean usesValueExpressionAsImplementation()
After this change id retrieval doesn't make the 1% YourKit profiler hot spot
cut off
