code: private static String transColumnNameToFieldName(String colName) {
  		if (StrUtils.isEmpty(colName))
  			return colName;
  		if (!colName.contains("_"))
  			return StrUtils.toLowerCaseFirstOne(colName);
  		StringBuilder sb = new StringBuilder();
  		char[] chars = colName.toLowerCase().toCharArray();
  		for (int i = 0; i < chars.length; i++) {
  			char c = chars[i];
  			if (c == '_')
  				continue;
  			if ((i > 0) && (chars[i - 1]) == '_' && sb.length() > 0)
  				sb.append(Character.toUpperCase(c));
  			else
  				sb.append(c);
  		}
  		return sb.toString();
  	}
docs: Map DB column name to entity field name, example: <br/>
  user_name -> userName <br/>
  USER_NAME -> userName <br/>
  User_naMe -> userName <br/>
  UserName -> userName <br/>
  USERNAME -> uSERNAME <br/>
  userName -> userName <br/>
  username -> username <br/>