At SourceClear I was recently tasked with finding a solution for dynamically creating cron expressions. As I had a look around at different open source tools, I couldn’t find exactly what we were looking for. Most of the libraries were very coupled to the DOM, essentially jQuery libraries, which didn’t fit our requirements. So I decided to create a tool to fit our needs and make it available as open source.
While adjusting some environment variables recently, I came across an odd issue with Docker, Spring Boot and JAVA_OPTS. JAVA_OPTS comes from the Tomcat/Catalina world and when searching for “Docker and javaopts” on Google you’ll find many references to just adding JAVA_OPTS to the Docker environment. After some testing, I found this to be incorrect when running a Spring Boot jar in a Docker container, I’ll explain why and give a solution in this post.