mybatis resultmap對映結果集(xml對映配置一)
阿新 • • 發佈:2019-01-26
自動對映例子
當資料庫名稱與pojo一致時候,可以直接自動對映
<select id="selectUsers" resultType="com.someapp.model.User">
select id, username, hashedPassword
from some_table
where id = #{id}
</select>
當資料庫名稱與pojo不一致時候,採用類型別名,比如:
<select id="selectUsers" resultType="User"> select user_id as "id", user_name as "userName", hashed_password as "hashedPassword" from some_table where id = #{id} </select>
ResultMap設計
使用外部的 resultMap 會怎樣,解決列名不匹配的另外一種方式。
資料庫column -> java pojo property
<resultMap id="userResultMap" type="User"> <id property="id" column="user_id" /> <result property="username" column="user_name"/> <result property="password" column="hashed_password"/> </resultMap>
其中id表示主鍵,對應xml檔案可配置如下
<select id="selectUsers" resultMap="userResultMap">
select user_id, user_name, hashed_password
from some_table
where id = #{id}
</select>
ResultMap高階結果對映
pojo物件
public class Employee { private Integer id; private String realName; private SexEnum sex; private Date birthday; private String mobile; private String email; private String position; private String note; private WorkCard workCard; private List<EmployeeTask> employeeTasks; }
xml配置檔案
<resultMap id="BaseResultMap" type="priv.dengjl.ns.bean.Employee">
<result column="id" jdbcType="INTEGER" property="id" />
<result column="real_name" jdbcType="VARCHAR" property="realName" />
<result column="sex" typeHandler="priv.dengjl.ns.handler.SexEnumHandler"
property="sex" />
<result column="birthday" jdbcType="DATE" property="birthday" />
<result column="mobile" jdbcType="VARCHAR" property="mobile" />
<result column="email" jdbcType="VARCHAR" property="email" />
<result column="position" jdbcType="VARCHAR" property="position" />
<result column="note" jdbcType="VARCHAR" property="note" />
<association column="id" property="workCard"
select="priv.dengjl.ns.mapper.WorkCardMapper.getWorkCardByEmpId" />
<collection column="id" property="employeeTasks"
select="priv.dengjl.ns.mapper.EmployeeTaskMapper.getEmployeeTaskListByEmpId" />
<discriminator column="sex" javaType="int">
<case value="1" resultMap="MaleEmployeeMap"/>
<case value="0" resultMap="FemaleEmployeeMap"/>
</discriminator>
</resultMap>
一對一 workCard物件
<association column="id" property="workCard"
select="priv.dengjl.ns.mapper.WorkCardMapper.getWorkCardByEmpId" />
一對多 workCard物件
<association column="id" property="workCard"
select="priv.dengjl.ns.mapper.WorkCardMapper.getWorkCardByEmpId" />
鑑別器
<discriminator column="sex" javaType="int">
<case value="1" resultMap="MaleEmployeeMap"/>
<case value="0" resultMap="FemaleEmployeeMap"/>
</discriminator>
其中select對應的值為單個檔案的xml配置
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