class DefaultHttpSession implements HttpSession {

    @Override
    public void setAttribute(String name, Object value) {
        verifyValid("setAttribute");
        if (value != null) {
            boolean added = true;
            if (attributes.containsKey(name)) {
                added = false;
            }
            Object oldValue = attributes.put(name, value);
            if (added) {
                sessionManager.attributeAdded(this, name, value);
            } else {
                sessionManager.attributeReplaced(this, name, oldValue, value);
            }
        } else {
            removeAttribute(name);
        }
    }

    public  DefaultHttpSession(ServletContext servletContext);
    public  DefaultHttpSession(ServletContext servletContext, String id, boolean newFlag);

}