gistfile1.php

<?php
class AppModel extends Model {

var $withFieldName = false;
var $error_messages = array();

function _setErrorMessageI18n() {
    $this->error_messages['empty'] = __('Error Hoge',true);
}

function beforeValidate(){
    $this->_setErrorMessageI18n();

    foreach( $this->validate as $fieldname  =>  $ruleSet ){
        foreach( $ruleSet as $rule => $rule_info ){

            if(!empty($this->validate[$fieldname][$rule]['rule'])) {
                $rule_option = $this->validate[$fieldname][$rule]['rule'];                               

            if( $error_message = $this->_getErrorMessageI18n( $rule ) ) {
                $this->validate[$fieldname][$rule]['message'] = vsprintf($error_message, $rule_option);

            }elseif( !empty($this->validate[$fieldname][$rule]['message']) ){
                $this->validate[$fieldname][$rule]['message'] = __( $this->validate[$fieldname][$rule]['message'], true);
            }

            if( $this->withFieldName && !empty($this->validate[$fieldname][$rule]['message']) ){
                $this->validate[$fieldname][$rule]['message'] = __( $fieldname ,true) . ' : ' . $this->validate[$fieldname][$rule]['message'];
            }
        }
    }
    return true;
}

function _getErrorMessageI18n( $rule ){

    if( array_key_exists($rule, $this->error_messages) ){
        return $this->error_messages[$rule];
    }else{
        return false;                    
    }
}