It sounds like a much older Java thing called JSR 168 Portlets. I remember briefly working with those in 2012, but Wikipedia says the spec is from 2003.

https://en.wikipedia.org/wiki/Java_Portlet_Specification

https://www.infoworld.com/article/2073645/introducing-the-po...

Edit: Actually, given the timing, I was probably using JSR 286 Portlets 2.0 (2008).