（转）java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.

jar包下载方式
官网地址：MySQL :: Download Connector/J，如果你打不开官网，在下面我为你准备了直接下载jar包的链接地址。

在选择操作系统时，此处选择platform independent（独立于平台）。

8.0版本的jar包下载地址，点击直接下载。

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.11.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.12.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.13.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.14.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.15.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.16.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.17.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.18.zip
https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.19.zip
https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.20.zip
https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.21.zip
https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.22.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.23.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.24.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.25.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.26.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.27.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.28.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-8.0.29.zip

5.0版本的jar包下载地址，点击直接下载。

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-5.1.47.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-5.1.48.zip

https://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-5.1.49.zip

于是我尝试将 5.1.39这个版本的数据库jar包，换成了我之前的 5.1.45版本，最终问题解决。输出了我想要的东西

————————————————
版权声明：本文为CSDN博主「Famiglistimott」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/kt1776133839/article/details/124539192