摘要：
插入操作的时候出现。Duplicate entry 'test' for key 1 。原因：由于数据库字段的惟一性约束，不允许重名的字段值存在。 阅读全文
摘要：
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.SocketExceptionMESSAGE: java.net.ConnectException: Connection timed out: connectSTACKTRACE:java.net.SocketException: java.net.ConnectException: Connection timed out: 阅读全文