Java vs. Let's Encrypt, How to Fix: Unable to find valid certification path to requested target
The connection of a java program to a service using SSL used to crash because Oracle delivers its JDK with an own store of trusted certificates.
The exception typically said something like
unable to find valid certification path to requested target.
There is one simple solution to work around this issue: update your JDK. The new certificate was added at the latest to JDK8U111.