code: private static String joinWhere(List<Field> fields, String logicOperate) {
  		StringBuilder sb = new StringBuilder();
  		int fieldSize = fields.size();
  		for(int i = 0; i < fieldSize; i++) {
  			Column column = fields.get(i).getAnnotation(Column.class);
  			sb.append(getColumnName(column)).append("=?");
  			if(i < fieldSize - 1) {
  				sb.append(" ").append(logicOperate).append(" ");
  			}
  		}
  		return sb.toString();
  	}
docs: 拼凑where子句。返回sql【不】包含where关键字
  @param fields
  @param logicOperate 操作符，例如AND
  @return