Liberty has built in support for JAX-RS, so you can easily implement this without any additional dependency. It’s very easy and you will the service setup in no time.
JAX-RS has gained the popularity over JAX-WS for many reasons, such as light weight, ability to invoke from Java Script, easy to setup etc.
If you want to find out how to setup Liberty you can follow my previous post on How to Setup Liberty. Here are the below steps on how to configure REST Service (JAX-RS) in IBM Liberty Profile.