JAVA-Warning: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.

警告：不建议在没有服务器证书验证的情况下建立SSL连接。根据MySQL5.5.45+，5.6.26+和5.7.6+的要求，如果不设置显式选项，SSL连接默认建立。为了符合现有的不使用SSL的应用，服务器的证书验证属性请设置为“false”。你需要设置useSSL=false或者useSSL=true来为服务器证书验证提供信任库。

解决措施：
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/testjdbc useSSL=false","root","123456");