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多对多:一个用户有多个角色,一个角色可以有多个用户。
表:user :id username birthday sex address
role : id role_name role_desc
user_role: uid rid
实体类:
Role:
private Integer roleId;
private String roleName;
private String roleDesc;
//多对多的关系映射:一个角色可以赋予多个用户
private List<User> users;
User:
private Integer id;
private String username;
private String address;
private String sex;
private Date birthday;
//多对多的关系映射:一个用户可以具备多个角色
private List<Role> roles;
IRoleDao.xml
<!--定义role表的ResultMap-->
<resultMap id="roleMap" type="role">
<id property="roleId" column="rid"></id>
<result property="roleName" column="role_name"></result>
<result property="roleDesc" column="role_desc"></result>
<collection property="users" ofType="user">
<id column="id" property="id"></id>
<result column="username" property="username"></result>
<result column="address" property="address"></result>
<result column="sex" property="sex"></result>
<result column="birthday" property="birthday"></result>
</collection>
</resultMap>
<!--查询所有-->
<select id="findAll" resultMap="roleMap">
select u.*,r.id as rid,r.role_name,r.role_desc from role r
left outer join user_role ur on r.id = ur.rid
left outer join user u on u.id = ur.uid
</select>
IRoleDao
List<Role> findAll();
IUserDao.xml
<!-- 定义User的resultMap-->
<resultMap id="userMap" type="user">
<id property="id" column="id"></id>
<result property="username" column="username"></result>
<result property="address" column="address"></result>
<result property="sex" column="sex"></result>
<result property="birthday" column="birthday"></result>
<!-- 配置角色集合的映射 -->
<collection property="roles" ofType="role">
<id property="roleId" column="rid"></id>
<result property="roleName" column="role_name"></result>
<result property="roleDesc" column="role_desc"></result>
</collection>
</resultMap>
<!-- 查询所有 -->
<select id="findAll" resultMap="userMap">
select u.*,r.id as rid,r.role_name,r.role_desc from user u
left outer join user_role ur on u.id = ur.uid
left outer join role r on r.id = ur.rid
</select>
IUserDao
List<User> findAll();
这样就可以关联查询对象了