JPA - Persistir numa tabela que tenha uma FK

-- Table: condômino
CREATE TABLE condomino
(
  con_codigo integer NOT NULL,
  con_cpf character(11),
  con_email character varying(50),
  con_password character(6),
  cod_apto integer,
  fun_nivel character(1),
  con_nome character varying(100),
  CONSTRAINT condomino_pkey PRIMARY KEY (con_codigo),
  CONSTRAINT apartamento_apa_codigo_fkey FOREIGN KEY (cod_apto)
      REFERENCES apartamento (apa_codigo) MATCH FULL
      ON UPDATE NO ACTION ON DELETE NO ACTION
) 
WITHOUT OIDS;

-- Table: apartamento
CREATE TABLE apartamento
(
  apa_codigo integer NOT NULL,
  apa_num integer,
  tor_codigo integer,
  CONSTRAINT apartamento_pkey PRIMARY KEY (apa_codigo),
  CONSTRAINT apartamento_tor_codigo_fkey FOREIGN KEY (tor_codigo)
      REFERENCES torre (tor_codigo) MATCH FULL
      ON UPDATE NO ACTION ON DELETE NO ACTION
) 
WITHOUT OIDS;

@WebService(serviceName = "GerenciarEncomendasWsApp")
@Stateless()
public class GerenciarEncomendasWsApp {
    @EJB
    CondominoFacadeRemote condominoFacadeBean;
    
    @WebMethod(operationName = "cadastrarCondomino")
    public void cadastrarCondomino(@WebParam(name = "cpf") String cpf, @WebParam(name = "email") String email, @WebParam(name = "password") String password, @WebParam(name = "codapto") Integer codapto, @WebParam(name = "nivelAcesso") String nivel, @WebParam(name = "nome") String nome) {
        //TODO write your implementation code here:
        condominoFacadeBean.adicionar(cpf, email, password, codapto, nivel, nome);
    }

public class CondominoFacade implements CondominoFacadeRemote, CondominoFacadeLocal {
    
    @PersistenceContext
    private EntityManager em;    
    @Override
    public void adicionar(String cpf, String email, String password, Integer codapto, String nivel, String nome) {
        Condomino condomino = new Condomino();      
        
        condomino.setConCodigo(gerarNovoCodigo());
        condomino.setConCpf(cpf);
        condomino.setConEmail(email);
        condomino.setConPassword(password);        
        condomino.setConNivel(nivel);
        condomino.setConNome(nome);       
        
        Apartamento apartamento = new Apartamento();
        apartamento.setApaCodigo(codapto);        
        condomino.setApaCodigo(apartamento);
        em.persist(condomino);
        
        //em.flush();
    }

    @Override
    public int gerarNovoCodigo() {
        String s;
        int n;
        if(em.createNamedQuery("Condomino.findAll").getResultList().isEmpty()){
            n=0;
        }else{
            s = em.createNamedQuery("Condomino.getMaxCodigo").getSingleResult().toString();
            n = Integer.parseInt(s);
        }
        return n+1;
    }
   . Mais coisas aqui
   .
   .
}

@Entity
@Table(name = "condomino",catalog = "", schema = "public")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Condomino.getMaxCodigo", query = "SELECT MAX(c.conCodigo) FROM Condomino c"),    
    @NamedQuery(name = "Condomino.findAll", query = "SELECT c FROM Condomino c"),
    @NamedQuery(name = "Condomino.findByConCodigo", query = "SELECT c FROM Condomino c WHERE c.conCodigo = :conCodigo"),
    @NamedQuery(name = "Condomino.findByConCpf", query = "SELECT c FROM Condomino c WHERE c.conCpf = :conCpf"),
    @NamedQuery(name = "Condomino.findByConEmail", query = "SELECT c FROM Condomino c WHERE c.conEmail = :conEmail"),
    @NamedQuery(name = "Condomino.findByConPassword", query = "SELECT c FROM Condomino c WHERE c.conPassword = :conPassword"),
    @NamedQuery(name = "Condomino.findByConNivel", query = "SELECT c FROM Condomino c WHERE c.conNivel = :conNivel"),
    @NamedQuery(name = "Condomino.findByNome", query = "SELECT c FROM Condomino c WHERE c.conNome = :conNome")})
public class Condomino implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @Basic(optional = false)
    @NotNull
    @Column(name = "con_codigo")
    private Integer conCodigo;
    @Size(max = 11)
    @Column(name = "con_cpf")
    private String conCpf;
    @Size(max = 20)
    @Column(name = "con_email")
    private String conEmail;
    @Size(max = 6)
    @Column(name = "con_password")
    private String conPassword;    
    @JoinColumn(name = "condomino.cod_apto", referencedColumnName = "apartamento.apa_codigo")
    @ManyToOne(optional = true)
    private Apartamento apaCodigo;
    @OneToMany(mappedBy = "conCodigo")
    private Collection<Encomenda> encomendaCollection;
    @Size(max = 1)
    @Column(name = "con_nivel")
    private String conNivel;
    @Size(max = 100)
    @Column(name = "con_Nome")
    private String conNome;   
    public Condomino() {
    }

    public Condomino(Integer conCodigo) {
        this.conCodigo = conCodigo;
    }

    public Integer getConCodigo() {
        return conCodigo;
    }

    public void setConCodigo(Integer conCodigo) {
        this.conCodigo = conCodigo;
    }

    public String getConCpf() {
        return conCpf;
    }

    public void setConCpf(String conCpf) {
        this.conCpf = conCpf;
    }

    public String getConEmail() {
        return conEmail;
    }

    public void setConEmail(String conEmail) {
        this.conEmail = conEmail;
    }

    public String getConPassword() {
        return conPassword;
    }

    public void setConPassword(String conPassword) {
        this.conPassword = conPassword;
    }

    public Apartamento getApaCodigo() {
        return apaCodigo;
    }

    public void setApaCodigo(Apartamento apaCodigo) {
        this.apaCodigo = apaCodigo;
    }

    @XmlTransient
    public Collection<Encomenda> getEncomendaCollection() {
        return encomendaCollection;
    }

    public void setEncomendaCollection(Collection<Encomenda> encomendaCollection) {
        this.encomendaCollection = encomendaCollection;
    }
    public void setConNivel(String conNivel) {
        this.conNivel = conNivel;
    }

    public String getConNivel() {
        return conNivel;
    }
    public void setConNome(String conNome) {
        this.conNome = conNome;
    }

    public String getConNome() {
        return conNome;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (conCodigo != null ? conCodigo.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Condomino)) {
            return false;
        }
        Condomino other = (Condomino) object;
        if ((this.conCodigo == null && other.conCodigo != null) || (this.conCodigo != null && !this.conCodigo.equals(other.conCodigo))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "org.ws.gerencdeencomendas.model.Condomino[ conCodigo=" + conCodigo + " ]";
    }

Classe Apartamento Gerada
    
}

package org.ws.gerencdeencomendas.model;

import java.io.Serializable;
import java.util.Collection;
import javax.persistence.*;
import javax.validation.constraints.NotNull;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlTransient;
/**
 * @author Administrador
 */
@Entity
@Table(name = "apartamento",catalog = "", schema = "public")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Apartamento.findAll", query = "SELECT a FROM Apartamento a"),
    @NamedQuery(name = "Apartamento.findByApaCodigo", query = "SELECT a FROM Apartamento a WHERE a.apaCodigo = :apaCodigo"),
    @NamedQuery(name = "Apartamento.findByApaNum", query = "SELECT a FROM Apartamento a WHERE a.apaNum = :apaNum")})
public class Apartamento implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @Basic(optional = false)
    @NotNull
    @Column(name = "apa_codigo")
    private Integer apaCodigo;
    @Column(name = "apa_num")
    private Integer apaNum;
    @JoinColumn(name = "tor_codigo", referencedColumnName = "tor_codigo")
    @ManyToOne
    private Torre torCodigo;
    @OneToMany(mappedBy = "apaCodigo")
    private Collection<Condomino> condominoCollection;
    @OneToMany(mappedBy = "apaCodigo")
    private Collection<Encomenda> encomendaCollection;

    public Apartamento() {
    }

    public Apartamento(Integer apaCodigo) {
        this.apaCodigo = apaCodigo;
    }

    public Integer getApaCodigo() {
        return apaCodigo;
    }

    public void setApaCodigo(Integer apaCodigo) {
        this.apaCodigo = apaCodigo;
    }

    public Integer getApaNum() {
        return apaNum;
    }

    public void setApaNum(Integer apaNum) {
        this.apaNum = apaNum;
    }

    public Torre getTorCodigo() {
        return torCodigo;
    }

    public void setTorCodigo(Torre torCodigo) {
        this.torCodigo = torCodigo;
    }

    @XmlTransient
    public Collection<Condomino> getCondominoCollection() {
        return condominoCollection;
    }

    public void setCondominoCollection(Collection<Condomino> condominoCollection) {
        this.condominoCollection = condominoCollection;
    }

    @XmlTransient
    public Collection<Encomenda> getEncomendaCollection() {
        return encomendaCollection;
    }

    public void setEncomendaCollection(Collection<Encomenda> encomendaCollection) {
        this.encomendaCollection = encomendaCollection;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (apaCodigo != null ? apaCodigo.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Apartamento)) {
            return false;
        }
        Apartamento other = (Apartamento) object;
        if ((this.apaCodigo == null && other.apaCodigo != null) || (this.apaCodigo != null && !this.apaCodigo.equals(other.apaCodigo))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "org.ws.gerencdeencomendas.model.Apartamento[ apaCodigo=" + apaCodigo + " ]";
    }
    
}