Java-Note-Mybatis-resultSet中一对多关系的转换

• 使用collection来将一对多的result set转换为实体类对象最后转化为json
• 最近被这个问题困扰, 而且中文的资料很少, 解决之后特地写下来与大家分享, 不足之处, 还请指出
• 例子:
  • result set:

  Columns: id, gmt_create, gmt_modify, is_active, sender_id, receiver_id, type, is_agreed, process_url, process_reason, id, gmt_create, gmt_modify, is_active, form_id, field_name, field_value
  Row: 1, 2018-04-18 18:58:06.0, 2018-04-18 18:58:06.0, 1, 19, 18, 0, null, null, null, 1, 2018-04-18 19:01:52.0, 2018-04-18 19:05:15.0, 1, 1, name, 德玛西亚
  Row: 1, 2018-04-18 18:58:06.0, 2018-04-18 18:58:06.0, 1, 19, 18, 0, null, null, null, 2, 2018-04-18 19:02:04.0, 2018-04-18 19:05:02.0, 1, 1, gender, 男
  Row: 1, 2018-04-18 18:58:06.0, 2018-04-18 18:58:06.0, 1, 19, 18, 0, null, null, null, 3, 2018-04-18 19:02:10.0, 2018-04-18 19:04:58.0, 1, 1, nation, 中国
  Row: 1, 2018-04-18 18:58:06.0, 2018-04-18 18:58:06.0, 1, 19, 18, 0, null, null, null, 4, 2018-04-18 19:02:16.0, 2018-04-18 19:04:54.0, 1, 1, birth, 19910526
  

  • 转换后的json:

  [
      {
          "id": 2,
          "gmtCreate": 1524050347000,
          "gmtModify": 1524050347000,
          "isActive": true,
          "senderId": 18,
          "receiverId": 20,
          "type": 1,
          "isAgreed": true,
          "processUrl": null,
          "processReason": null,
          "customFormFields": [
              {
                  "id": 18,
                  "gmtCreate": 1524050438000,
                  "gmtModify": 1524050438000,
                  "isActive": true,
                  "formId": 2,
                  "fieldName": "社会组织名称",
                  "fieldValue": "2"
              },
              {
                  "id": 19,
                  "gmtCreate": 1524050472000,
                  "gmtModify": 1524050472000,
                  "isActive": true,
                  "formId": 2,
                  "fieldName": "法人登记证",
                  "fieldValue": "2"
              },
              {
                  "id": 20,
                  "gmtCreate": 1524050481000,
                  "gmtModify": 1524050481000,
                  "isActive": true,
                  "formId": 2,
                  "fieldName": "单位地址",
                  "fieldValue": "2"
              },
              {
                  "id": 21,
                  "gmtCreate": 1524050489000,
                  "gmtModify": 1524050489000,
                  "isActive": true,
                  "formId": 2,
                  "fieldName": "成立日期",
                  "fieldValue": "2"
              }
          ]
      }
  ]
  

• 方法: 在resultMap中使用collection,
  • 参考资料: 官方文档 http://www.mybatis.org/mybatis-3/sqlmap-xml.html
  • 官方文档中的原话: collection – a collection of complex types nested result mappings – collections are resultMaps themselves, or can refer to one
  • 实践:
    • 其中的property填入一对多中"一"这一方(称之为A, 多称为B)的实体类中的代表B的列表的成员变量名, 在本例中为customFormFields
    • ofType填B的完全限定名, 本例中为com.jeecms.cms.entity.CustomFormField
    • 下一层填id和result
  • 例:
  • 注意: 字段名(包括column中)要用as做替换, 否则result set取出来为多行, 最后mybatis转换出来只有一行!!!
    • 替换示例:

    
        custom_form.id as custom_form_id, custom_form.gmt_create as custom_form_gmt_create,custom_form.gmt_modify as custom_form_gmt_modify,custom_form.is_active as custom_form_is_active,custom_form.sender_id as custom_form_sender_id, custom_form.receiver_id as custom_form_receiver_id,
        custom_form.type as custom_form_type, custom_form.is_agreed as custom_form_is_agreed, custom_form.process_url as custom_form_process_url, custom_form.process_reason as custom_form_process_reason