Controlling custom component rendering

Question

As I'm writing my own custom components, I've come across some behaviorisms of JSF that don't quite make sense to me. I thought I'd ask the group, and see if someone can clarify it.
Let's say I've got a JSP with the following components on it:
<myfaces:comp1>
<myfaces:comp2>
<myfaces:comp3/>
</myfaces:comp2>
</myfaces:comp1>
Let's assume that the UIComponent representing comp2 contains the following snippets:
public boolean getRenderChildren() {
return true;
public void encodeBegin(FacesContext context) throws IOException {
// render something here....
public void encodeChildren(FacesContext context) throws IOException {
Iterator iter = this.getChildren();
while (iter.hasNext()) {
UIComponent child = (UIComponent)iter.next();
child.encodeBegin(context);
if (child.getRenderChildren()) {
child.encodeChildren(context);
child.encodeEnd(context);
public void encodeEnd(FacesContext context) throws IOException {
// render something here....
All the other components return false for getRenderChildren();
During the Rendering Phase, I find that comp3
is actually rendered twice.
This is an oversimplification of the code I was experimenting with, but what puzzled me was the fact that whatever class is traversing the various components during Rendering Phase does not seem to check whether a component is going to render its children itself, and as it comes to that child component (in this case, comp3), it renders it anyhow. Then when comp2's encodeChildren() method is called, it too renders comp3.
I suspect I may misunderstand how these methods are used..
Rob

Answer 1

During the Rendering Phase, I find that comp3
is actually rendered twice.
This is an oversimplification of the code I was
experimenting with, but what puzzled me was the fact
that whatever class is traversing the various
components during Rendering Phase does not seem to
check whether a component is going to render its
children itself, and as it comes to that child
component (in this case, comp3), it renders it anyhow.
Then when comp2's encodeChildren() method is called,
it too renders comp3.Yes, Suns reference implementation does not seem to check whether a component's parent has set the "encodeChildren" attribute to true.
Well, the open source implementation "MyFaces" (http://sourceforge.net/projects/myfaces/) does this.
What's not so clear is the following question:
When a component is rendered by it's parent and itself has the "encodeChildren" attribute set to false, should children of this component automatically be rendered, or not? In other words: Whenever a component has the "encodeChildren" attribute set to true, is it responsible for rendering all children and grandchildren (and grand-grandchildren...)?
The final Specification should state this clearly, I think.
Manfred