mybatis注解开发一对一、一对多

超、凢脫俗 2022-11-03 15:23 177阅读 0赞

# 一对一 #

package cn.gpxxg.dao;
    
    import cn.gpxxg.domain.Account;
    import org.apache.ibatis.annotations.One;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import org.apache.ibatis.mapping.FetchType;
    
    import java.util.List;
    
    public interface AccountDao {
        @Select("select * from account")
        @Results( id = "accountMap", value = {
          @Result(id = true, property = "id", column = "id"),
          @Result(property = "uid", column = "uid"),
          @Result(property = "money", column = "money"),
          @Result(property = "user", column = "uid", one = @One(select = "cn.gpxxg.dao.UserDao.findById", fetchType = FetchType.EAGER))
        })
        List<Account> findAll();
    
        @Select("select * from account where uid = #{idd}")
        List<Account> findListByUid(Integer uid);
    }

一对多

package cn.gpxxg.dao;
    
    import cn.gpxxg.domain.User;
    import org.apache.ibatis.annotations.*;
    import org.apache.ibatis.mapping.FetchType;
    
    import java.util.List;
    
    public interface UserDao {
        /**
         * 查询所有
         * @return
         */
        @Select("select * from user")
        @Results( id = "userMap", value = {
                @Result(id=true, property = "userId", column = "id"),
                @Result(property = "userBirthday", column = "birthday"),
                @Result(property = "userGender", column = "gender"),
                @Result(property = "userTelephone", column = "telephone"),
                @Result(property = "accounts", column = "id", many = @Many(select = "cn.gpxxg.dao.AccountDao.findListByUid", fetchType = FetchType.LAZY))
        })
        public abstract List<User> findAll();
    
        /**
         * 查询一个
         */
        @Select("select * from user where id = #{id}")
        @ResultMap(value={"userMap"}) // 可以简写为@ResultMap("userMap")
        public abstract User findById(Integer userId);
    
        /**
         * 根据用户名模式查询
         */
        @Select("select * from user where username like #{username}")
        @ResultMap("userMap")
        public abstract List<User> findListByUserName(String username);
    }

总结

1、一对一时使用one = @One(select = "cn.gpxxg.dao.UserDao.findById", fetchType = FetchType.EAGER)

2、一对多时使用many = @Many(select = "cn.gpxxg.dao.AccountDao.findListByUid", fetchType = FetchType.LAZY)

3、其中select是查询另一个表的全限定类名+方法名，fetchType是加载方式，FetchType.EAGER是即时加载，FetchType.LAZY是延迟加载