I'd suggest project structure like this:
loader (POM, multi-module)
+ loader-api (JAR)
+ crawler1 (JAR, depends on loader-api)
+ crawler2 (JAR, depends on loader-api)
+ loader-app (JAR, depends on loader-api, crawler1, crawler2.
The standalone app is built here)
By splitting the API that crawlers depends and the app itself, the whole project structure is much easier to manage. And, it is more modularized too, as we are no longer mixing the API with the app