Answering this assumes knowing the competing ecosystems - I don't. I have been working in the Java ecosystem for over a decade and haven't had the urge to look

Answering this assumes knowing the competing ecosystems - I don't. I have been working in the Java ecosystem for over a decade and haven't had the urge to look for greener pastures. Libraries/frameworks that, if they went away, would make me look for a new ecosystem: - JUnit (Unit testing) - Mockito (stubbing) - Selenium - Spring (mostly for dependency injection, secondly for the many useful adapters) - Hibernate (I'm off Hibernate now but there were times I couldn't do without it) - Tomcat - Cocoon (afaik dead now, but I've written massive applications with it) - Swing (desktop apps used to be a thing when I was young)