Apache Tomcat - 用于部署的语言和工具

For context, I developed a web application using JS & HTML that allows a user to manually upload a log file (from a shared folder on a Tomcat server) and display errors, info, etc based on the format of the log file.

However, say I want to cut the user upload, and automatically retrieve files from the Tomcat server (running on an Apache instance - so web app would be deployed on the Apache box) and then display the information on a web page - would I need to use a java servlet, or could I use php with js? I doubt that I could do it server-side with JS? Any advice?

Yes, you'd need something on the server side (e.g a java servlet, a php page) to grab the content from the server and make it available to client side (e.g html+js).