Can't make something on Isis

[Juan Martin Buireo]

Hi, I am with a problem trying to implement something on Apache Isis.
Here is what I want to do:
I have a class Country that has a String with the name of the country. Also
I have a class called Client which represents a client with the following
variables: String name, String surname, String address, Country country. I
made the setters and getters for all the properties. I also have the
classes Countries and Clients. Both of this classes have the methods create
and listAll. My problem is: I want to create a new Client and when I create
it, I want to have a select with the countries that I already persisted.
The problem is that I can't achieve this. I send the classes done on
attachment to understand how I am doing it. But basically is that what I
want, that when I create a new client, this one has a name, surname and
address to complete and a select with the countries that I already
persisted.
Thank you

public class Client {
	

	private String name;
	private String surname;
	private String address;
	private Country country;

	@javax.jdo.annotations.Column(allowsNull = "false")
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
	
	@javax.jdo.annotations.Column(allowsNull = "false")
	public String getSurname() {
		return surname;
	}

	public void setSurname(String surname) {
		this.surname = surname;
	}

	@javax.jdo.annotations.Column(allowsNull = "false")
	public String getAddress() {
		return address;
	}

	public void setCountry(String address) {
		this.address = address;
	}

	@javax.jdo.annotations.Column(allowsNull = "false")
	public String getCountry() {
		return country;
	}

	public void setCountry(Country country) {
		this.country = country;
	}	

	// I have the injects with the domainContainer	
}

public class Clients {
	
	@ActionSemantics(Of.SAFE)
	public Client create(final @Named("Nombre") String name, final @Named("Apellido") String surname, final @Named("Direccion") String address, final @Named("Pais") Country country) {
		final Client client = newTransientInstance(Client.class);
		client.setName(name);
		client.setSurname(surname);
		client.setAddress(address);
		client.setCountry(country);
		persist(client);
		return client;
	}

	@ActionSemantics(Of.SAFE)
	public List<Client> listAll() {
        	return container.allInstances();
    	}

	// I have the injects with the domainContainer

}

public class Country {
	
	@ActionSemantics(Of.SAFE)
	public Country create(final @Named("Pais") String country) {
		final Country c = newTransientInstance(Country.class);
		c.setCountry(country);
		persist(c);
		return c;
	}

	@ActionSemantics(Of.SAFE)
	public List<Country> listAll() {
        	return container.allInstances();
    	}

	// I have the injects with the domainContainer

}

public class Country {
	
	private String country;

	@javax.jdo.annotations.Column(allowsNull = "false")
	public String getCountry() {
		return country;
	}

	public void setCountry(Country country) {
		this.country = country;
	}

	// I have the injects with the domainContainer

}