详解mybatis中association和collection的column传入多个参数问题

项目中在使用association和collection实现一对一和一对多关系时需要对关系中结果集进行筛选，如果使用懒加载模式，即联合使用select标签时，主sql和关系映射里的sql是分开的，查询参数传递成为问题。

mybatis文档:

property	description
column	数据库的列名或者列标签别名。与传递给resultSet.getString(columnName)的参数名称相同。注意： 在处理组合键时，您可以使用column=“{prop1=col1,prop2=col2}”这样的语法，设置多个列名传入到嵌套查询语句。这就会把prop1和prop2设置到目标嵌套选择语句的参数对象中。

<resultMap id="findCountryCityAddressMap" type="map">
 <result property="country" column="country"/>
 <collection property="cityList"
    column="{cityId=city_id,adr=addressCol,dis=districtCol}" //adr作为第二个sql查询条件key,即prop1属性
    ofType="map"            //addressCol即为虚拟列名
    javaType="java.util.List" select="selectAddressByCityId"/>
</resultMap>

<resultMap id="selectAddressByCityIdMap" type="map">
 <result property="city" column="city"/>
 <collection property="addressList" column="city" ofType="map" javaType="java.util.List">
  <result property="address" column="address"/>
  <result property="district" column="district"/>
 </collection>
</resultMap>

<select id="findCountryCityAddress" resultMap="findCountryCityAddressMap">
 SELECT
  ct.country,ci.city_id,IFNULL(#{addressQuery},'') addressCol,//为传入查询条件,构造虚拟列，虚拟列为查询条件参数值
  IFNULL(#{districtQuery},'') districtCol
 FROM
  country ct
 LEFT JOIN city ci ON ct.country_id = ci.country_id
 ORDER BY ct.country_id
</select>

<select id="selectAddressByCityId" parameterType="java.util.Map" resultMap="selectAddressByCityIdMap">
 SELECT
  ci.city,ads.address,ads.district
 FROM
  (
   SELECT
    city,city_id
   FROM
    city ci
   WHERE
    ci.city_id = #{cityId}
  ) ci
 LEFT JOIN address ads ON ads.city_id = ci.city_id
 <where>
  <if test="adr!=null and adr!=''">
   and ads.address RegExp #{adr}
  </if>
  <if test="dis!=null and dis!=''">
   ads.district Regexp #{dis}
  </if>
 </where>

</select>

测试文件:

@Test
public void findCountryCityAddressTest() throws JsonProcessingException {
 Map<String,Object> param = new HashMap<>();
 param.put("addressQuery","1168");
 List<Map<String,Object>> rs = countryManager.findCountryCityAddress(param);
 ObjectMapper mapper = new ObjectMapper();
 ObjectWriter writer = mapper.writerWithDefaultPrettyPrinter();
 System.out.println(writer.writeValueAsString(rs));
}

测试结果:

[
 {
  "country": "Afghanistan","cityList": [{
    "city": "Kabul","addressList": [{
      "address": "1168 Najafabad Parkway","district": "Kabol"
     }
    ]
   }
  ],"city_id": 251
 },{
  "country": "Algeria","cityList": [],"city_id": 59
 }
]

可以看到，确实将查询条件通过column参数传入到第二个sql中，并执行成功

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