MyBatis @Result和@Many注解详解：关联查询与映射配置教程

@Results(id="groupWithUsers",
         value = { 
            @Result(property = "groupId", column = "group_id", id = true),
            @Result(property = "name", column = "name"), 
            @Result(property = "accountId", column = "account_id"),
            @Result(property = "deleteFlag", column = "delete_Flag"),
            @Result(property = "parentId", column = "parent_Id"), 
            @Result(property = "userList", javaType=List.class, many =@Many(select="selectUsersByGroupId"), column = "group_id")})
//查询
@Select({"select * from group where account_id=#{accountId} and delete_flag=0"})
List<Group> selectGroupWithUsers(@Param("accountId") String accountId);
@Select({"select u.* from user u",
		"inner join user_group ug on u.user_id = ug.user_id",
		"where ug.group_id=#{groupId} and u.delete_flag=0"
		})
List<User> selectUsersByGroupId(@Param("groupId") String groupId);

@Data
public class Group {
    private String groupId;
    private String name;
    private String accountId;
    private String parentId;
    private String type;
    private List<User> userList;
}

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface Results {
    String id() default "";  //当前Results注解的唯一标识
    Result[] value() default {};  //value值为Result[]数组
}

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({})
public @interface Result {
    boolean id() default false;  //id唯一标识
    String column() default "";  //对应数据库中的列名
    String property() default ""; //对应类中的属性名
    Class<?> javaType() default void.class;  //数据类型
    JdbcType jdbcType() default JdbcType.UNDEFINED;  //jdbc类型
    Class<? extends TypeHandler> typeHandler() default UnknownTypeHandler.class;
    One one() default @One;  //一对一配置
    Many many() default @Many;  //一对多配置
}

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({})
public @interface Many {
    String select() default "";  //选择要执行的方法
    FetchType fetchType() default FetchType.DEFAULT;  //枚举值，懒加载、及时加载、默认
}

@Result(property = "userList", javaType=List.class, many =@Many(select="selectUsersByGroupId"), column = "group_id")})

public List<User> selectUsers(Map<String,Object> map);

column = "{groupId=group_id, userName=user_name}"

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface ResultMap {
    String[] value();
}

@ResultMap("resultsId")
@Select("......")
List<Object> select();