mybatis_plus一对一实体映射

场景：查询中间表对应的用户和角色，这里一条中间表数据分别只对应一个用户和一个角色。固然通常不会有这样的需求，这里只是举例一对一关系.

1、数据结构

一、用户表

二、角色表

三、中间表

2、xml自定义sql

<resultMap type="com.xiao.permission_system.entity.UerRole" id="BaseColumn">
     <id column="id" property="id" />
     <result column="uid" property="uid" />
     <result column="role_id" property="roleId" />
     <association property="users" javaType="com.xiao.permission_system.entity.UserInfo">
         <id column="id" property="id" />
         <result column="username" property="username" />
         <result column="password" property="password" />
     </association>
     <association property="roles" javaType="com.xiao.permission_system.entity.Role">
         <id column="id" property="id" />
         <result column="name" property="name" />
     </association>
 </resultMap>

 <sql id="base">
  ur.uid,
  ur.role_id
</sql>

 <sql id="userColumn">
   u.id,
   u.username,
   u.password
 </sql>

 <sql id="roleColumn">
     r.id,
     r.name
 </sql>

 <select id="getRoles" resultMap="BaseColumn">
     select
     <include refid="base" />,
     <include refid="userColumn" />,
     <include refid="roleColumn" />
     from sys_uer_role ur
     LEFT JOIN sys_user_info u on u.id=ur.uid
     LEFT join sys_role r on
     r.id=ur.role_id
     where
     uid=#{uid}
 </select>

3、中间表实体

@Data
@EqualsAndHashCode(callSuper = true)
@Accessors(chain = true)
@TableName("sys_uer_role")
public class UerRole extends BaseEntity{

    private static final long serialVersionUID = 1L;

    /**
     * 主键
     */
    @TableId()
    private String id;

    private String uid;

    private String roleId;

    private UserInfo users;

    private Role roles;
}