URL in the
Jenkins container uses the name of MySQL container, or the private IP in the docker network has been connected successfully.
Java app, write in URL. If you use the container name, report
java.net.UnknownHostException: db
(db is the name of MySQL container)
if you write a private address, report
java.net.SocketTimeoutException: connect timed out
two containers are connected in the same bridge network of docker