返回格式处理——嵌套返回结果集

有些时候，我们需要拼接一些sql查询结果，作为vo的返回。比如下面这个vo，除了返回一些基础字段以外，还会返回一些子列表来表示多条信息。当然子列表还会继续套子列表。
举例如下：

public class CooperationLandVo implements Serializable {
    /**
     * updateFlag(新增：flase ；更新 true)
     */
    @JSONField(ordinal=1)
    protected Boolean updateFlag;
    /**
     * 合作机构id
     */
    @JSONField(ordinal=2)
    protected String cooperationId;
    /**
     * 合作机构名称
     */
    @JSONField(ordinal=3)
    protected String cooperationName;
    /**
     * 合作机构code
     */
    @JSONField(ordinal=4)
    protected String cooperationCode;
    /**
     * 合作状态（0：未合作，1：合作中，2：停止合作）
     */
    @JSONField(ordinal=5)
    protected String cooperateStatus;
    /**
     * 合作开始时间
     */
    @JSONField(ordinal=6,format="yyyy-MM-dd HH:mm:ss")
    protected Date cooperateStartTime;
    /**
     * 合作结束时间
     */
    @JSONField(ordinal=7,format="yyyy-MM-dd HH:mm:ss")
    protected Date cooperateEndTime;
    /**
     * 优先级权重
     */
    @JSONField(ordinal=8)
    protected Integer weight;

    /**
     * 机构类型：资方/险方
     */
    @JSONField(ordinal = 9)
    protected CooperationLandBaseDto.Type bigType;

    /**
     * 机构小类
     */
    @JSONField(ordinal = 10)
    protected Integer type;

    @JSONField(ordinal=12)
    List cooperationLandCompanyVoList;

    @JSONField(ordinal=11)
    List cooperationLandProductVoList;

其中，CooperationLandCompanyVo下又带有子列表CooperationLandSubcapVo

public class CooperationLandCompanyVo implements Serializable {
    /**
     * 合作机构id
     */
    @JSONField(serialize=false)
    protected String cooperationId;
    /**
     * 分公司编码
     */
    protected String companyCode;

    /**
     * 落地城市名称
     */
    protected String cityName;

    /**
     * 落地城市id
     */
    protected String cityId;

    /**
     * 启用人
     */
    protected String createUserName;

    /**
     * 启用人id
     */
    protected String createUserId;

    /**
     * 启用时间
     */
    @JSONField(format="yyyy-MM-dd HH:mm:ss")
    protected Date groundTime;

    /**
     * 下级机构
     */
    List cooperationLandSubcapVoList;
}

对于这样的结构，我想通过mybatis的查询直接获取到这个结构，我就需要拼装和嵌套resultMap。
如下：
这里我想问有没有不需要写resultMap就能返回嵌套结果的情况。比如直接使用某种方式，返回类型为resultType之类的，如果大神看到，求评论，求私信

然后对于其中的cooperationLandCompanyVoList这个子集合，返回也是用一个resultMap，嵌套下级机构的返回集合。如下：

接着是三个嵌套部分的子查询：
我们设置了关联的column为cooperationId（看resultMap的collection列），但是对于实际的返回，我们不需要这一列的信息，因为在主查询中，已经获取了。
所以我们可以去掉在sql中对于这一列的“as”操作，也就是不将他映射至vo中。但是鉴于CooperationLandCompanyVo本身需要再次和下级嵌套，所以它的cooperationId是不可以省略的（如果没有这里的第二层嵌套关系，就可以全部省略）
这样，在最终获取结果集的时候，对于没有的子查询，不会返回[{}]（如果设置了不序列化cooperationId），而是[]。
前端展示时就不会多一条空记录了。
同样的，这里的

    
        SELECT
        distinct bccl.coop_capital_id,
        bccl.capital_id as subCapitalId,
        bccl.capital_code as subCapitalCode,
        bccl.capital_name as subCapitalName,
        bccl.bank_code as bankCode,
        bcci.bank_name as bankName
        FROM
        b_cooperate_capital_land bccl
        
        left join b_cooperate_bank_info bcci on bccl.bank_code = bcci.bank_code
        WHERE
        bccl.delete_flag='0'
        and
        bccl.coop_capital_id = #{cooperationId}
        AND
        bccl.company_code = #{companyCode}
    
    
    
        SELECT
        distinct bccl.coop_capital_id as cooperationId,
        bccl.city_name as cityName,
        bccl.company_code as companyCode,
        bccl.ground_time as groundTime,
        bccl.ground_user_id as createUserId,
        su.fullname_ as createUserName
        FROM
        b_cooperate_capital_land bccl
        left join sys_user su on su.id_ = bccl.ground_user_id
        WHERE
        bccl.delete_flag='0'
        and
        bccl.coop_capital_id = #{cooperationId}
    
    
    
        SELECT
        distinct bccl.coop_capital_id ,
        bccl.product_id as productId,
        bp.product_name as productName,
        bpn.loan_node_name as loanNodeName,
        bccl.loan_node as loanNode
        FROM
        b_cooperate_capital_land bccl
        left join b_product bp on bp.product_id = bccl.product_id
        left join b_product_node bpn on bp.product_id = bpn.product_id and bccl.loan_node = bpn.loan_node_code
        WHERE
        bccl.delete_flag='0'
        and
        bccl.coop_capital_id = #{cooperationId}
    

    
    
        select
        bcc.capital_id as cooperationId,
        bcc.capital_name as cooperationName,
        bcc.capital_code as cooperationCode,
        bcc.cooperate_start_time as cooperateStartTime,
        bcc.cooperate_end_time as cooperateEndTime,
        bcc.cooperate_status as cooperateStatus,
        bcc.weight as weight,
        (
        SELECT
        IF (
        bcc.capital_type = 'bank',
        0,1)
        )
        AS `type`,
        'CAP' as `bigType`,
        (select IF(count(id) > 0, TRUE, FALSE) as e from b_cooperate_capital_land
        where coop_capital_id = bcc.capital_id) as updateFlag
        from
        b_cooperate_capital bcc
        left join b_cooperate_capital_land bccl on bccl.coop_capital_id = bcc.capital_id
        where
        bccl.delete_flag='0'
        and
        bcc.delete_flag = '0'
        and
        bcc.capital_id = #{cooperationId}
        limit 1
    

如果是没有双层嵌套，这样已经满足了，返回类型直接是CooperationLandVo即可。但是如果存在这样的嵌套。需要在外层继续操作一下，手动去掉它。

 public CooperationLandVo getCapitalLandInfoDetail(String cooperationId) {
        //这里其实已经查询完毕了，下面的操作都是为了去掉空对象。
        CooperationLandVo cooperationLandVo = cooperateCapitalLandManager.getLandInfoDetail(cooperationId);
        if(CollectionUtils.isEmpty(cooperationLandVo.getCooperationLandCompanyVoList())||cooperationLandVo.getCooperationLandCompanyVoList().get(0)==null){
            cooperationLandVo.setCooperationLandCompanyVoList(new ArrayList());
        }else{
            List cooperationLandCompanyVos = cooperationLandVo.getCooperationLandCompanyVoList();
            for(CooperationLandCompanyVo cooperationLandCompanyVo:cooperationLandCompanyVos){
                if(CollectionUtils.isEmpty(cooperationLandCompanyVo.getCooperationLandSubcapVoList())||cooperationLandCompanyVo.getCooperationLandSubcapVoList().get(0)==null){
                    cooperationLandCompanyVo.setCooperationLandSubcapVoList(new ArrayList());
                }
            }
        }
        if(CollectionUtils.isEmpty(cooperationLandVo.getCooperationLandProductVoList())||cooperationLandVo.getCooperationLandProductVoList().get(0)==null){
            cooperationLandVo.setCooperationLandProductVoList(new ArrayList());
        }
        return cooperationLandVo;
    }

返回结果：

{
    "code": "0000",
    "isSuccess": true,
    "msg": "成功",
    "result": {
        "updateFlag": true,
        "cooperationId": "0000000000",
        "cooperationName": "招商银行",
        "cooperationCode": "ZSYX",
        "cooperateStatus": "1",
        "cooperateStartTime": "2017-09-12 00:00:00",
        "cooperateEndTime": "2020-09-12 00:00:00",
        "weight": 0,
        "bigType": "CAP",
        "type": 0,
        "cooperationLandProductVoList": [
            {
                "loanNode": "XXX",
                "loanNodeName": "XXXXXX",
                "productId": "XXXXX",
                "productName": "XXXXX"
            }
        ],
        "cooperationLandCompanyVoList": [
            {
                "cityName": "上海市",
                "companyCode": "021000",
                "cooperationLandSubcapVoList": [
                    {
                        "bankCode": "XXXX",
                        "subCapitalCode": "122222",
                        "subCapitalId": "22222222",
                        "subCapitalName": "xx银行"
                    },
                    {
                        "bankCode": "XXXXXXX",
                        "bankName": "交通银行",
                        "subCapitalId": "3333333"
                    }
                ],
                "createUserId": "1",
                "createUserName": "系统管理员",
                "groundTime": "2019-10-24 15:09:38"
            },
            {
                "cityName": "淮安市",
                "companyCode": "517170",
                "cooperationLandSubcapVoList": [],
                "createUserId": "1111",
                "createUserName": "XXX",
                "groundTime": "2017-11-16 18:29:13"
            },
            {
                "cityName": "东莞市",
                "companyCode": "769000",
                "cooperationLandSubcapVoList": [],
                "createUserId": "1222",
                "createUserName": "XXXX",
                "groundTime": "2017-11-16 18:23:13"
            }
        ]
    },
    "success": true
}