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：

  1.     mysql> select user,plugin from mysql.user;
  2.     +------------------+-----------------------+
  3.     | user             | plugin                |
  4.     +------------------+-----------------------+
  5.     | root             | caching_sha2_password |
  6.     | mysql.infoschema | mysql_native_password |
  7.     | mysql.session    | mysql_native_password |
  8.     | mysql.sys        | mysql_native_password |
  9.     | root             | caching_sha2_password |
  10.     +------------------+-----------------------+

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：

  1. 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：

  1.     mysql> select host,user,plugin from mysql.user;
  2.     +-----------+------------------+-----------------------+
  3.     | host      | user             | plugin                |
  4.     +-----------+------------------+-----------------------+
  5.     | %         | root             | caching_sha2_password |
  6.     | localhost | mysql.infoschema | mysql_native_password |
  7.     | localhost | mysql.session    | mysql_native_password |
  8.     | localhost | mysql.sys        | mysql_native_password |
  9.     | localhost | root             | mysql_native_password |
  10.     +-----------+------------------+-----------------------+
  11.     5 rows in set (0.00 sec)

将这个用户也改了：

  1. ALTER USER 'root'@'%' IDENTIFIED WITH mysql_native_password BY 'root';

再看：

  1.     mysql> select host,user,plugin from mysql.user;
  2.     +-----------+------------------+-----------------------+
  3.     | host      | user             | plugin                |
  4.     +-----------+------------------+-----------------------+
  5.     | %         | root             | mysql_native_password |
  6.     | localhost | mysql.infoschema | mysql_native_password |
  7.     | localhost | mysql.session    | mysql_native_password |
  8.     | localhost | mysql.sys        | mysql_native_password |
  9.     | localhost | root             | mysql_native_password |
  10.     +-----------+------------------+-----------------------+

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。