从数据库取数据

方法一

            String sql="SELECT parentEquipmentId` FROM xy_measuringpoint_list group by parentEquipmentId`";
            Connection conn= DriverManager.getConnection("jdbc:mysql://localhost:3306/znkk","root","root");
            Statement stmt=conn.createStatement();
            conn.setAutoCommit(false);//更改jdbc事务的默认提交方式
            ResultSet resultSet=stmt.executeQuery(sql);////得到结果集
            conn.commit();//提交
            conn.setAutoCommit(true);
            List<String> deviceIds=new ArrayList<>();
            while (resultSet.next()){
                deviceIds.add(resultSet.getString(1));
            }

方法二
在xml文件编辑

    <select id="findDeviceId" resultType="java.lang.String">
        select parentEquipmentId from xy_measuringpoint_list
    </select>

dao

List<String> findDeviceId();

service

List<String> findDeviceId();

serviceImpl

 @Override
    public List<String> findDeviceId() {
        List<String> deviceIds= xyMeasuringpointListDao.findDeviceId();
        return deviceIds;
    }

使用（Impl）

List<String> deviceIds=measuringpointListService.findDeviceId();