JAX-RS Hello World Application

HelloWorldResource.java

import javax.inject.Singleton;
import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;

@Path("helloworld")
@Singleton
public class HelloWorldResource {
    
    private String hello = "Hello World!";
    
    @GET
    @Produces("text/plain")
    public String getHello() {
        return hello;
    }

    @POST
    @Consumes("text/plain")
    public void postHello(String hello) {
        this.hello = hello;
    }

}

JaxRsApplication.java

import java.util.Set;
import java.util.HashSet;
import javax.ws.rs.ApplicationPath;
import javax.ws.rs.core.Application;

@ApplicationPath("/")
public class JaxRsApplication extends Application {

    @Override
    public Set<Class<?>> getClasses() {
        Set<Class<?>> classes = new HashSet<>();
        classes.add(HelloWorldResource.class);
        return classes;
    }

}