How to mock a web server for unit testing in Java?

Try Simple(Maven) its very easy to embed in a unit test. Take the RoundTripTest and examples such as the PostTest written with Simple. Provides an example of how to embed the server into your test case.

Also Simple is much lighter and faster than Jetty, with no dependencies. So you won't have to add several jar files onto your classpath. Nor will you have to be concerned with WEB-INF/web.xml or any other artifacts.