mysql字符串转数组，合并结果集，转成数组

1.使用GROUP_CONCAT函数将多个结果集合并

2.使用CONCAT函数将结果集加[ ]

3.实体类接收数据

    private String id;

    private String name;

    private String[] item;

如果上面方法不行，就自定义注解处理

    @TableField(typeHandler = ArrayStringTypeHandler.class, jdbcType = JdbcType.VARCHAR)
    private String[] item;

/**
 *  存储到数据库, 将String数组转换成字符串;
 *  从数据库获取数据, 将字符串转为LONG数组.
 */
@MappedTypes({String[].class})
@MappedJdbcTypes({JdbcType.VARCHAR})
public class ArrayStringTypeHandler extends BaseTypeHandler<String[]> {

	private static String[] l = new String[]{};

	@Override
	public void setNonNullParameter(PreparedStatement ps, int i,
									String[] parameter, JdbcType jdbcType) throws SQLException {
		ps.setString(i, JSONUtil.toJsonStr(parameter));
	}

	@Override
	public String[] getNullableResult(ResultSet rs, String columnName)
			throws SQLException {
		return JSONUtil.parseArray(rs.getString(columnName)).toArray(l);
	}

	@Override
	public String[] getNullableResult(ResultSet rs, int columnIndex)
			throws SQLException {
		return JSONUtil.parseArray(rs.getString(columnIndex)).toArray(l);
	}

	@Override
	public String[] getNullableResult(CallableStatement cs, int columnIndex)
			throws SQLException {
		return JSONUtil.parseArray(cs.getString(columnIndex)).toArray(l);
	}

}