Mybatis中使用注解的形式开发

Mybatis中使用注解的形式开发

使用注解方式实现复杂映射开发

  实现复杂关系映射之前我们可以在映射文件中通过配置resultMap来实现，使用注解开发后，我们可以使用@Results注解，@Result注解，@One注解，@Many注解组合完成复杂关系的配置

使用注解模式开发记得在mybatis的核心配置文件中配置加载映射关系

    <!--加载映射关系-->
    <mappers>
        <!--指定接口所在的包-->
        <package name="com.duanping.mapper"/>
    </mappers>

一对一查询的注解开发

对应的sql语句：

    select * from orders;
    
    select * from user where id=查询出订单的uid;

使用注解的方式配置mapper

public interface OrdersMapper {
    
    @Select("select * from orders")
    @Results({

            @Result(column ="id" ,property = "id"),
            @Result(column ="ordertime" ,property = "ordertime"),
            @Result(column ="total" ,property = "total"),
            @Result(
                    property = "user",//要封装的属性名称
                    column = "uid",//根据哪个字段去查询user表的数据
                    javaType = User.class,//要封装的实体类型
                    one = @One(select = "com.duanping.mapper.UserMapper.findById")
            )

    })
    public List<Orders> findAll();
    
}

public interface UserMapper {

    @Select("select * from user where id=#{id}")
    List<User> findById(int id);

}

测试结果：

一对多查询的注解开发

对应的sql语句：

    select * from user;
    
    select * from orders where uid=查询出用户的id;
    

使用注解的方式配置mapper：

public interface UserMapper {

    @Select("select * from user")
    @Results({

            @Result(column = "id",property = "id"),
            @Result(column = "username",property = "username"),
            @Result(column = "password",property = "password"),
            @Result(
                    property = "ordersList",
                    column = "id",
                    javaType = List.class,
                    many = @Many(select = "com.duanping.mapper.OrdersMapper.findOrdersByUid")
            )
    })
    public List<User> findUserWithOrders();

}

public interface OrdersMapper {

    @Select("select * from orders where uid= #{uid}")
    public List<Orders> findOrdersByUid(int uid);

}

测试结果：

多对多查询的注解开发

对应的sql语句：

select * from user
SELECT * FROM sys_user_role ur, sys_role r WHERE ur.roleid=r.id AND ur.userid=查询出用户的id;

使用注解的方式配置mapper：

public interface UserMapper {


    @Select("select * from user")
    @Results({
            @Result(column = "id" ,property = "id"),
            @Result(column = "username" ,property = "username"),
            @Result(column = "password" ,property = "password"),
            @Result(
                    property = "roleList",
                    column = "id",
                    javaType = List.class,
                    many = @Many(select = "com.duanping.mapper.RoleMapper.findById")

            )
    })
    public List<User> findUserAndRole();

}

public interface RoleMapper {

    @Select("SELECT * FROM sys_user_role ur, sys_role r WHERE ur.roleid=r.id AND ur.userid=#{id}")
    public List<Role> findById(int id);
}

测试结果：