@Override
    public int doStartTag() throws JspException {
        // The I18nTag should be our parent Tag
        parent = (SidebarTag)findAncestorWithClass(this, SidebarTag.class);

        // If I18nTag was not our parent, throw Exception
        if (parent == null) {
            throw new JspTagException("SubSidebarTag with out a parent which is expected to be a SidebarTag");
        }
        return EVAL_BODY_BUFFERED;
    }
Looks for the parent SidebarTag class, throws an error if not found. If found,
{@link #EVAL_BODY_BUFFERED} is returned.

@return {@link #EVAL_BODY_BUFFERED} if no errors.
@throws javax.servlet.jsp.JspException if a parent SidebarTag is not found.
xmppserver/src/main/java/org/jivesoftware/admin/SubSidebarTag.java