Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure

这个错误通常是由于应用程序无法连接到MySQL数据库服务器引起的。这可能是由于以下原因导致的：

1. MySQL服务器未启动或已停止。
2. MySQL服务器正在使用的端口号与应用程序配置的端口号不同。
3. 防火墙或网络问题导致应用程序无法连接到MySQL服务器。
4. 应用程序使用的MySQL驱动程序版本与MySQL服务器版本不兼容。

你可以检查一下以上原因，看看是不是其中的一个导致了连接失败的问题。

相关问题

caused by: com.mysql.cj.exceptions.cjcommunicationsexception: communications link failure

这是一个 MySQL 通信链接错误异常，通常是由于与 MySQL 服务器的连接中断导致的。可能的原因包括 MySQL 服务器暂时不可用、连接超时、用户名或密码错误等。建议检查服务器的连接状态以及配置信息，并确保所有必要的端口都已打开。

Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure The last

This error message usually indicates a problem with the connection between your application and the MySQL database server. Here are a few things you can try to troubleshoot the issue:

1. Check your network connection: Make sure that your application server can communicate with the MySQL server. Ensure that there are no network issues, such as firewalls or network congestion.

2. Check MySQL server status: Verify that the MySQL server is up and running and that it's listening on the correct port. You can use the command "sudo systemctl status mysql" to check the status of the MySQL server.

3. Check MySQL logs: Check the MySQL error logs for any errors that may be causing the connection failure. The logs are usually located at /var/log/mysql/error.log.

4. Check MySQL configuration: Verify that the MySQL configuration is correct and that the connection parameters in your application code are correct. Check that the database name, username, and password are correct.

5. Increase the connection timeout: If the connection is timing out, increase the connection timeout in your application code or MySQL configuration file.

6. Restart MySQL server: Try restarting the MySQL server to clear any cached connections or other issues that may be causing the problem.

I hope this helps you resolve the issue. Let me know if you have any other questions.