I'm new to java and would like to create a RESTFUL API but I don't know which library to use or how to use it. Can anyone direct me to good tutorials or some libraries to study.
I would like to use JSON.
There are several options for working with REST in Java. There is an implementation of the Spring Framework (Spring MVC) and the JEE JAX-RS standard , which has several implementations, among which I see being most used are Jersey and RESTEasy .
Something you should consider is your production environment. Since JBoss Application Server comes with RESTEasy, it makes sense to adopt this implementation if you use JBoss, as it will make your life easier. I've already deployed an application with Jersey on a JBoss AS 7.1 and I can say that it wasn't without difficulties, to the point where I needed to change configuration files of the container modules. On the other hand, if your application server is Glassfish, it will be easier to go with Jersey which, like Glassfish, is the reference implementation.