mybatis中的resultmap的具体使用

github链接：https://github.com/AbitGo/mybatis_csdn/tree/master/workspace_mybatis_0x02

如下的resulttype的实现方式：

        select u.id,
        u.user_name userName,
        u.user_password userPassword,
        u.user_email userEmail,
        u.user_info userInfo,
        u.head_img headImg,
        u.create_time create_time,
        
        r.id "role.id",
        r.role_name "role.roleName",
        r.enabled "role.enabled",
        r.create_time "role.create_time",
        r.create_by "role.create_by"
        from sys_user u
        inner join sys_user_role ur on u.id = ur.user_id
        inner join sys_role r on ur.role_id = r.id
        where u.id = #{id}
    

在resultmap的实现中则需要这样
 

        select u.id,
        u.user_name,
        u.user_password,
        u.user_email,
        u.user_info,
        u.head_img,
        u.create_time,
        
        r.id role_id,
        r.role_name role_Name,
        r.enabled role_enabled,
        r.create_time role_create_time,
        r.create_by role_create_by
        from sys_user u
        inner join sys_user_role ur on u.id = ur.user_id
        inner join sys_role r on ur.role_id = r.id
        where u.id = #{id}
    


        
        
        
        
        
        
        
        
        
        
        
        
        

    

程序员还是懒得嘛，并且MyBatis也是支持resultMap映射继承的。所以演化成下面的xml。

        select u.id,
        u.user_name,
        u.user_password,
        u.user_email,
        u.user_info,
        u.head_img,
        u.create_time,
        
        r.id role_id,
        r.role_name role_Name,
        r.enabled role_enabled,
        r.create_time role_create_time,
        r.create_by role_create_by
        from sys_user u
        inner join sys_user_role ur on u.id = ur.user_id
        inner join sys_role r on ur.role_id = r.id
        where u.id = #{id}
    

        
        
        
        
        
        
        
    

        
        
        
        
        
    

再往后，程序员还是觉得麻烦，就这样写

        select u.id,
        u.user_name,
        u.user_password,
        u.user_email,
        u.user_info,
        u.head_img,
        u.create_time,
        
        r.id role_id,
        r.role_name role_Name,
        r.enabled role_enabled,
        r.create_time role_create_time,
        r.create_by role_create_by
        from sys_user u
        inner join sys_user_role ur on u.id = ur.user_id
        inner join sys_role r on ur.role_id = r.id
        where u.id = #{id}
    


    
        
        
        
        
        
        
        
    


        
        
            
            
            
            
            
        

最后，就发展成了这样子

        select u.id,
        u.user_name,
        u.user_password,
        u.user_email,
        u.user_info,
        u.head_img,
        u.create_time,
        
        r.id role_id,
        r.role_name role_role_Name,
        r.enabled role_enabled,
        r.create_time role_create_time,
        r.create_by role_create_by
        from sys_user u
        inner join sys_user_role ur on u.id = ur.user_id
        inner join sys_role r on ur.role_id = r.id
        where u.id = #{id}