warn: establishing ssl connection without server's identity verification is not recommended. according to mysql 5.5.45+, 5.6.26+ and 5.7.6+ requirements ssl connection must be established by default if explicit option isn't set. for compliance with existing applications not using ssl the verifyservercertificate property is set to 'false'. you need either to explicitly disable ssl by setting usessl=false, or set usessl=true and provide truststore for server certificate verification.

这段信息的含义是，建议不要在未进行服务器身份验证的情况下建立SSL连接。根据MySQL 5.5.45+、5.6.26+和5.7.6+的要求，如果没有明确设置选项，则必须默认建立SSL连接。为了符合不使用SSL的现有应用程序，verifyservercertificate属性被设置为“false”。你需要显式地将usessl设置为false来禁用SSL，或将usessl设置为true并提供truststore以进行服务器证书验证。