Request handling

abstract class RequestHandler {

  public static function getValue($code,$required=false,$default=null) {
    if (isset($_REQUEST[$code])) {
      return $_REQUEST[$code];
    } else {
      if ($required) {
        throwError("parameter '$code' not found in Request");
        exit;
      } else {
        return $default;
      }  
    }
  }
  
  public static function getClass($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidClass($val);
  }
  
  public static function getId($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidId($val);
  }
  
  public static function getNumeric($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidNumeric($val);
  }
  
  public static function getAlphanumeric($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidAlphanumeric($val);
  }
  
  public static function getDatetime($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidDateTime($val);
  }
  
  public static function getYear($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidYear($val);
  }
  
  public static function getMonth($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidMonth($val);
  }
  public static function getExpected($code,$expectedList) {
    $val=self::getValue($code,true,null);
    if (in_array($val, $expectedList)) {
      return $val;
    } else {
      throwError("parameter $code='$val' has an unexpected value");
      exit;
    }
  }
  
}