mysql错误：this authentication plugin is not supported

this authentication plugin is not supported

应用程序连接mysql docker一直报错：this authentication plugin is not supported。
google发现，原来是mysql新版本（8.0以上）将root用户使用的plugin更新成caching_sha2_password。
登录mysql输入如下命令可以看到：

mysql> select user,plugin from mysql.user;
+------------------+-----------------------+
| user | plugin |
+------------------+-----------------------+
| root | caching_sha2_password |
| mysql.infoschema | mysql_native_password |
| mysql.session | mysql_native_password |
| mysql.sys | mysql_native_password |
| root | caching_sha2_password |
+------------------+-----------------------+

解决办法有：
（1）降级，使用老版本mysql。
（2）将root的plugin改成mysql_native_password。
这里改成：

ALTER USER ‘root’@’localhost’ IDENTIFIED WITH mysql_native_password BY ‘root’;

这行代码有两层含义，第一:修改root的密码为’root’，摒弃原来的旧密码。第二：使用mysql_native_password对新密码进行编码。

然后再启动应用，还是一样报错。再看mysql.user,发现还有一个host”%”的root用户：

mysql> select host,user,plugin from mysql.user;
+-----------+------------------+-----------------------+
| host | user | plugin |
+-----------+------------------+-----------------------+
| % | root | caching_sha2_password |
| localhost | mysql.infoschema | mysql_native_password |
| localhost | mysql.session | mysql_native_password |
| localhost | mysql.sys | mysql_native_password |
| localhost | root | mysql_native_password |
+-----------+------------------+-----------------------+
5 rows in set (0.00 sec)

将这个用户也改了：
ALTER USER ‘root’@’%’ IDENTIFIED WITH mysql_native_password BY ‘root’;
再看：

mysql> select host,user,plugin from mysql.user;
+-----------+------------------+-----------------------+
| host | user | plugin |
+-----------+------------------+-----------------------+
| % | root | mysql_native_password |
| localhost | mysql.infoschema | mysql_native_password |
| localhost | mysql.session | mysql_native_password |
| localhost | mysql.sys | mysql_native_password |
| localhost | root | mysql_native_password |
+-----------+------------------+-----------------------+

改成功了，再启动应用，报错：
this user requires mysql native password authentication
在连接mysql的url上加上?allowNativePasswords=true，这次正常了。
---------------------