OIM UI Customization - Code Snippet to display ADF Error Message Pop Up.

public void displayErrorMessage(ActionEvent invokeEvent, String message) {
        String logp = CN + " :: displayErrorMessage- ";
        LOGGER.debug(logp + " START");

        FacesMessage facesMsg = new FacesMessage();
        facesMsg.setSeverity(FacesMessage.SEVERITY_ERROR);
        facesMsg.setSummary(message);
         FacesContext.getCurrentInstance().addMessage(invokeEvent.getComponent().getClientId(FacesContext.getCurrentInstance()),facesMsg);

        LOGGER.debug(logp + " END");
    }

Happy Learning!!!