public static UIComponent addTransient(
      FacesContext context, ServletRequest req, UIComponent parent, String prevId, Class childClass)
      throws Exception {
    if (context == null) context = FacesContext.getCurrentInstance();

    if (parent == null) {
      UIComponentClassicTagBase parentTag =
          (UIComponentClassicTagBase) req.getAttribute("caucho.jsf.parent");

      parent = parentTag.getComponentInstance();

      BodyContent body = parentTag.getBodyContent();

      if (body != null) addVerbatim(parent, body);
    }

    UIComponent child = null;
    ;

    if (child == null) child = (UIComponent) childClass.newInstance();

    child.setTransient(true);

    addChild(parent, prevId, child);

    return child;
  }
  public static UIComponent addFacet(
      FacesContext context,
      ServletRequest req,
      UIComponent parent,
      String facetName,
      ValueExpression binding,
      Class childClass)
      throws Exception {
    if (context == null) context = FacesContext.getCurrentInstance();

    if (parent == null) {
      UIComponentClassicTagBase parentTag =
          (UIComponentClassicTagBase) req.getAttribute("caucho.jsf.parent");

      parent = parentTag.getComponentInstance();
    }

    UIComponent child = null;

    if (binding != null) child = (UIComponent) binding.getValue(context.getELContext());

    if (child == null) child = (UIComponent) childClass.newInstance();

    if (parent != null) parent.getFacets().put(facetName, child);

    if (binding != null) binding.setValue(context.getELContext(), child);

    return child;
  }
  public static UIComponent addPersistent(
      FacesContext context,
      ServletRequest req,
      UIComponent parent,
      ValueExpression binding,
      Class childClass)
      throws Exception {
    if (context == null) context = FacesContext.getCurrentInstance();

    if (parent == null) {
      UIComponentClassicTagBase parentTag =
          (UIComponentClassicTagBase) req.getAttribute("caucho.jsf.parent");

      parent = parentTag.getComponentInstance();

      BodyContent body = parentTag.getBodyContent();

      addVerbatim(parent, body);
    }

    UIComponent child = null;

    if (binding != null) child = (UIComponent) binding.getValue(context.getELContext());

    if (child == null) {
      child = (UIComponent) childClass.newInstance();

      // jsf/3251
      if (binding != null) binding.setValue(context.getELContext(), child);
    }

    if (parent != null) parent.getChildren().add(child);

    return child;
  }
  public static UIComponent findPersistent(
      FacesContext context, ServletRequest req, UIComponent parent, String id) throws Exception {
    if (context == null) context = FacesContext.getCurrentInstance();

    BodyContent body = null;

    if (parent == null) {
      UIComponentClassicTagBase parentTag =
          (UIComponentClassicTagBase) req.getAttribute("caucho.jsf.parent");

      parent = parentTag.getComponentInstance();

      body = parentTag.getBodyContent();
    }

    if (parent != null) {
      List<UIComponent> children = parent.getChildren();
      int size = children.size();

      String prevId = null;
      for (int i = 0; i < size; i++) {
        UIComponent child = children.get(i);

        if (id.equals(child.getId())) {
          if (body != null) addVerbatim(parent, prevId, body);

          return child;
        }

        if (child.getId() != null) prevId = child.getId();
      }
    }

    return null;
  }
  public static UIComponent findFacet(
      FacesContext context, ServletRequest req, UIComponent parent, String facetName)
      throws Exception {
    if (context == null) FacesContext.getCurrentInstance();

    if (parent == null) {
      UIComponentClassicTagBase parentTag =
          (UIComponentClassicTagBase) req.getAttribute("caucho.jsf.parent");

      parent = parentTag.getComponentInstance();
    }

    if (parent != null) return parent.getFacet(facetName);
    else return null;
  }
  public static UIViewRoot findRoot(FacesContext context, ServletRequest req, Object etag)
      throws Exception {
    if (context == null) context = FacesContext.getCurrentInstance();

    UIViewRoot root = context.getViewRoot();

    if (root == null)
      throw new NullPointerException(L.l("f:view can't find current in FacesContext"));

    Object oldETag = root.getAttributes().get("caucho.etag");

    if (oldETag != null && !oldETag.equals(etag)) {
      // clear view on JSP change

      root.getChildren().clear();
      root.getFacets().clear();
    }

    root.getAttributes().put("caucho.etag", etag);

    return root;
  }