It's the other way round as always. You can compress the communication between Apache along with a J2EE server despite the fact that the customer may not blending the content?
Browser <- compressed or otherwise -> Apache <- always compressed -> Jetty
Really, so far as I understand, AJP is definitely uncompressed. It's assumed that the web and application servers are "close" enough (when it comes to network topology) to one another that compression isn't helpful, and merely slows things lower in the extra CPU processing.
If you are using HTTP between Apache and Jetty, you'll be able to configure compression, yes, though I have not use Jetty and should not let you know how you can configure that.