SQLException: An attempt by a client to checkout a Connection has timed out

SQLException: An attempt by a client to checkout a Connection has timed out

在测试黑马JavaWeb连接池成C3P0时报错:
java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
如图：

原因分析：****中用的mysql驱动是：mysql-connector-java-5.1.37-bin.jar
我的测试环境mysql8.0，用的驱动是：mysql-connector-java-8.0.17.jar。
所以配置文件c3p0-config.xml中修改成mysql8.0的配置，修改后的配置如下：
com.mysql.cj.jdbc.Driver
jdbc:mysql://localhost:3306/db4?useSSL=false&serverTimezone=UTC

测试运行，终于是我想要的结果了