OBSOLETE
THIS PROJECT IS NO LONGER MAINTAINED. PLEASE SEE https://github.com/webbit/webbit-rest FOR A MORE RECENT ALTERNATIVE.
Webbit REST brings JAX-RS (JSR-311) to Webbit. Here is a quick example:
package org.webbitserver.rest;
import org.webbitserver.WebServer;
import org.webbitserver.WebServers;
import org.webbitserver.rest.resteasy.ResteasyHandler;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
public class Main {
    @Path("/hello")
    public static class HelloResource {
        @GET
        @Produces("text/plain")
        public String get() {
            return "Hello";
        }
    }
    public static void main(String[] args) throws Exception {
        WebServer webServer = WebServers.createWebServer(9877);
        webServer.add(new ResteasyHandler(new HelloResource()));
        webServer.start();
        System.out.println("Try this: curl " + webServer.getUri() + "hello");
    }
}
Webbit-REST uses RestEasy under the hood.