for #398

1. [ISSUE #387](https://github.com/shardingjdbc/sharding-jdbc/issues/387) 当函数+列名中存在'`'防止关键字时处理出错

1. [ISSUE #394](https://github.com/shardingjdbc/sharding-jdbc/issues/394) 无法单独close statement

1. [ISSUE #398](https://github.com/shardingjdbc/sharding-jdbc/issues/398) 使用Hint路由屏蔽表和列名称的大小写区别

## 1.5.4.1

import lombok.EqualsAndHashCode;

import lombok.Getter;

import lombok.RequiredArgsConstructor;

/**

 * Sharding key.

 * @author zhangliang

 */

// TODO move to a suitable package

@RequiredArgsConstructor

@EqualsAndHashCode

public final class ShardingKey {

     */

    @Getter

    private final String shardingColumn;

    public ShardingKey(final String logicTable, final String shardingColumn) {

        this.logicTable = logicTable.toLowerCase();

        this.shardingColumn = shardingColumn.toLowerCase();

    }

}