mybatis---一对一,一对多
一、一对一
实体类
//多对一(mybatis中称之为一对一)的映射:一个账户只能属于一个用户 private User user; public User getUser() { return user; } public void setUser(User user) { this.user = user; }
接口
/** * 查询所有账户,并且获取每个账户所属的用户信息 * @return */ @Select("select * from account") @Results(id="accountMap",value = { @Result(id=true,column = "id",property = "id"), @Result(column = "uid",property = "uid"), @Result(column = "money",property = "money"), @Result(property = "user",column = "uid",one=@One(select="com.itheima.dao.IUserDao.findById",fetchType= FetchType.EAGER)) })
二、一对多
接口
IAccountDao
List<Account> findAll(); /** * 根据用户id查询账户信息 * @param userId * @return */ @Select("select * from account where uid = #{userId}") List<Account> findAccountByUid(Integer userId);
IUserDao
@Select("select * from user") @Results(id="userMap",value={ @Result(id=true,column = "id",property = "userId"), @Result(column = "username",property = "userName"), @Result(column = "address",property = "userAddress"), @Result(column = "sex",property = "userSex"), @Result(column = "birthday",property = "userBirthday"), @Result(property = "accounts",column = "id", many = @Many(select = "com.itheima.dao.IAccountDao.findAccountByUid", fetchType = FetchType.LAZY)) }) List<User> findAll();
实体类
//一对多关系映射:一个用户对应多个账户 private List<Account> accounts; public List<Account> getAccounts() { return accounts; } public void setAccounts(List<Account> accounts) { this.accounts = accounts; }