Here is code that I use to do this dynamically, but it is re-traversing the whole tag tree when needed.

If you already have a reference to the component, you can just use the second method called "getFullComponentId" to get the full id.

/**
 * Search the JSF Tree for a component based only on its partial component ID (i.e.,
 * without the NamingContainer)
 * @author matt.pickell
 */
public class JSFTreeComponentFinder {

 /**
 * Recursively search for the partial componentID in the JSF tree. If found, return its absolute ID.
 * @param partialComponentId the id that the component was created with. NOT containing the NamingContainer
 * @return the full ID, with naming container for using in finding this component in the JSF Tree.
 * Or null if no component exists with that partial ID
 */
 public static String buildAbsoluteComponentIDFromJsfTree(String partialComponentId, UIComponent root) {
 if (root.getChildCount() > 0) {
 for (Object next : root.getChildren()) {
 UIComponent current = (UIComponent) next;
 if (partialComponentId.equals(current.getId())) {
 return getFullComponentId(current);
 } else {
 if (current.getChildCount() > 0) {
 String subTreeHunt = buildAbsoluteComponentIDFromJsfTree(partialComponentId, current);
 if (subTreeHunt != null) {
 return subTreeHunt;
 }
 }
 }
 }
 }
 return null;
 }

 /**
 * Once a component is known in the JSF tree, this returns its absolute ID
 * @param component build absolute ID based on JSF Tree structure.
 * @return the absolute ID of the component.
 */
 public static String getFullComponentId(UIComponent component) {
 String fullId = component.getId();

 component = component.getParent();
 while (component != null) {
 if (component instanceof NamingContainer) {
 fullId = component.getId() + NamingContainer.SEPARATOR_CHAR + fullId;
 }
 component = component.getParent();
 }

 return fullId;
 }

}