Mybatis多层嵌套查询

基于权限管理时的用户角色权限处理。

实体类：

　　1.User

　　public class User{
    private Integer uid;
    private String username;
    private String password;
    private Set<Role> roles=new HashSet<>();
　2.Role

　　public class Role {
    private Integer rid;
    private String rname;
    private Set<Module> modules=new HashSet<>();
　3.Module
　　

Mapper 文件。

 <resultMap id="userMap2" type="com.example.mapper.entity.User">
        <id property="uid" column="uid"/>
        <result property="username" column="username"/>
        <result property="password" column="password"/>
        <collection property="roles" ofType="roleMap" column="uid" select="findRole"></collection>
    </resultMap>

    <resultMap id="roleMap" type="com.example.mapper.entity.Role">
        <id property="rid" column="rid"/>
        <result property="rname" column="rname"/>
        <collection property="modules" ofType="com.example.mapper.entity.Module" column="rid" select="findModule">
        </collection>
    </resultMap>

      <select id="findUserByUserName" parameterType="java.lang.String" resultMap="userMap2">
          SELECT  * from USER WHERE username=#{username}
      </select>

    <select id="findRole" parameterType="java.lang.Integer" resultMap="roleMap">
        SELECT r.* from Role r LEFT  JOIN  user_role ur on ur.rid =r.rid where ur.uid=#{uid}
    </select>

    <select id="findModule" parameterType="java.lang.Integer" resultType="com.example.mapper.entity.Module">
        SELECT m.* from module m LEFT  JOIN  module_role mr on mr.mid =m.mid where mr.rid=#{rid}
    </select>

　　测试结果。

User{uid=1, username='hlhdidi', password='123', roles=[Role{rid=1, rname='admin',modules=[Module{mid=2, mname='delete'}, Module{mid=3, mname='query'}, Module{mid=4, mname='update'}, Module{mid=1, mname='add'}]}]}