The most common cause of ClassNotFoundException is a problem downloading the correct driver.

I have a pro license and is using QStudio 2.03 on Windows
Do you know why I cannot connect to Clickhouse ?
1/ Host: https:// ...
2/ Server type Clickhouse
I got error when test connection: ClassNotFoundException (ru.yandex.clickhouse.ClickhouseDriver)

How Drivers Work

QStudio has a small number of drivers builtin (mysql/postgresql/kdb..), to prevent requiring a massive installer, most other drivers are downloaded on demand. If you get a ClassNotFoundException either:

  • The driver is not downloading - possibly due to connection or firewall issue
  • The driver is not being saved to it's directory - file write permissions
  • The driver is failing to be loaded dynamically - Java JRE permissions error
To find out which check logs.

Check QStudio Logs

check the logs to see what is happening:

  • On windows you can run: C:\Program Files (x86)\TimeStored.com\qstudio-log.bat
  • QStudio on windows keeps a log file at C:\Users\{USERNAME}\QStudio
  • On mac/linux, you can run 
    java -jar QStudio.jar
     to get a version that logs to console.
If you are in any doubt, you can email us the logs. Note you should take care to only email NON-Sensitive information.

Example successful log

Immediately after you click yes, you should get a log similar to that shown below:

Driver Download

See Also