[TRINIDAD] [API] [TRINIDAD-2398] add component tracking ability to RequestContext

[Jing Wu]

Hi,

Please review the following API proposal for adding component tracking 
ability to RequestContext

[TRINIDAD] [API] [TRINIDAD-2398] add component tracking ability to 
RequestContext
https://issues.apache.org/jira/browse/TRINIDAD-2398

Requirement:

There are cases where we need to know which component is under 
processing. This can be achieved if we maintain component stack in 
RequestContext and provide API to push/pop/peek the component stack. 
Components are pushed/popped when they are decoded, validated, rendered, 
visited, etc.

For performance reason, we would like to have VisitContext keep a 
reference to the current RequestContext.

New API Proposed:

3 new methods added to RequestContext for component tracking ability. 
Default implementation is to do nothing. The methods are not abstract 
for backward compatibility reason.

  /**
   * Push the component onto the stack so we know the current component 
being processed.
   * @param context the FacesContext for the current request
   * @param component an UIComponent object to be pushed as current 
component.
   * @exception NullPointerException if <code>component</code> is null.
   * @see popCurrentComponent(FacesContext, UIComponent) and 
getCurrentComponent()
   */
  public void pushCurrentComponent(FacesContext context, UIComponent 
component)
  {
    return;
  }

  /**
   * Pop the component out from the stack.
   * @param context the FacesContext for the current request
   * @param component an UIComponent object to be poped.
   * @exception IllegalStateException if <code>component</code> is not 
the same
   * as the current top component in the component stack.
   * @see pushCurrentComponent(FacesContext, UIComponent) and 
getCurrentComponent()   */
  public void popCurrentComponent(FacesContext context, UIComponent 
component)
  {
    return;
  }

  /**
   * Returns the current component being processed.
   * @see pushCurrentComponent(FacesContext, UIComponent) and 
popCurrentComponent(FacesContext, UIComponent)
   */
  public UIComponent getCurrentComponent()
  {
    return null;
  }


2. New method added to VisitContext to retrieve RequestContext instance. 
Subclasses can hold a reference to the current RequestContext instance 
and return that reference.

  /**
   * <p>Returns the RequsetContext instance for the current request.</p>
   */
  public RequestContext getRequestContext()
  {
    return RequestContext.getCurrentInstance();
  }


Thanks,
Jing