public AjaxRequestBuilder update(UIComponent component, String expressions, boolean ignoreNoResult) {
        addExpressions(component, expressions, "u", ignoreNoResult ? HINTS_UPDATE_IGNORE_NO_RESULT : HINTS_UPDATE);

        return this;
    }
Helper to generate javascript code of an ajax call
primefaces/src/main/java/org/primefaces/util/AjaxRequestBuilder.java