Question

Is it possible to declare a composite-component in such a way that it can just be placed inside certain tags?

E.g that:

<span>
    <n:myComponent/>
</span>

would be illegal, while:

<div>
    <n:myComponent/>
</div>

would be legal.

Answer 1

Not during buildtime, but during rendertime you could check the siblings of the component.

public void encodeChildren(FacesContext context) {
    List<UIComponent> children = getParent().getChildren();
    // Loop over children until you find a child which equals to "this".
    // Then check if the previous and next sibling contains <span> and </span>.
    // ...

    if (valid) {
        super.encodeChildren(context);
    } else {
        throw new IllegalArgumentException("n:myComponent can't be placed inside <span>");
    }
} 

You can do this in an UINamingContainer implementation which is as @FacesComponent referenced by <cc:interface componentType>.