SOAP object returns null

Question

I'm having some simple objects that have relationships with each other. Everything goes fine but when i publish my objects for a SOAP request it is returning null when i set a relation between client and cartrack. What am i doing wrong?

Here is my code :

@Entity
public class Client extends User implements Serializable {
    @Temporal(javax.persistence.TemporalType.DATE)
    private Date birthdate;
    private String address;
    private String zipcode;
    private String city;
    private String phone;
    private String info;
    private boolean active;
    @OneToMany( cascade = CascadeType.ALL,
                fetch = FetchType.EAGER,
                targetEntity = Cartrack.class, 
                mappedBy = "client"
                )
    private List<Cartrack> cartracks;

    /**
     * @return the birthdate
     */
    public Date getBirthdate() {
        return birthdate;
    }

    /**
     * @param birthdate the birthdate to set
     */
    public void setBirthdate(Date birthdate) {
        this.birthdate = birthdate;
    }

    /**
     * @return the address
     */
    public String getAddress() {
        return address;
    }

    /**
     * @param address the address to set
     */
    public void setAddress(String address) {
        this.address = address;
    }

    /**
     * @return the zipcode
     */
    public String getZipcode() {
        return zipcode;
    }

    /**
     * @param zipcode the zipcode to set
     */
    public void setZipcode(String zipcode) {
        this.zipcode = zipcode;
    }

    /**
     * @return the city
     */
    public String getCity() {
        return city;
    }

    /**
     * @param city the city to set
     */
    public void setCity(String city) {
        this.city = city;
    }

    /**
     * @return the phone
     */
    public String getPhone() {
        return phone;
    }

    /**
     * @param phone the phone to set
     */
    public void setPhone(String phone) {
        this.phone = phone;
    }

    /**
     * @return the info
     */
    public String getInfo() {
        return info;
    }

    /**
     * @param info the info to set
     */
    public void setInfo(String info) {
        this.info = info;
    }

    public String dateToString(){
        SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
        return formatter.format(this.birthdate);
    }

    public boolean isActive() {
        return active;
    }

    public void setActive(boolean active) {
        this.active = active;
    }

    public List<Cartrack> getCartracks() {
        return cartracks;
    }

    public void setCartracks(List<Cartrack> cartracks) {
        this.cartracks = cartracks;
    }
}

@Entity
public class Cartrack implements Serializable {

    @Id
    private String id;
    @OneToOne(  mappedBy = "cartrack", 
                targetEntity = Vehicle.class,
                cascade = CascadeType.ALL,
                fetch = FetchType.EAGER
            )
    private Vehicle vehicle;
    @ManyToOne(targetEntity = Client.class)
    private Client client;

    /**
     * @return the id
     */
    public String getId() {
        return id;
    }

    /**
     * @param id the id to set
     */
    public void setId(String id) {
        this.id = id;
    }

    /**
     * @return the vehicle
     */
    public Vehicle getVehicle() {
        return vehicle;
    }

    /**
     * @param vehicle the vehicle to set
     */
    public void setVehicle(Vehicle vehicle) {
        this.vehicle = vehicle;
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof Cartrack)) {
            return false;
        }
        return ((Cartrack) obj).id == this.id;
    }

    public Client getClient() {
        return client;
    }

    public void setClient(Client client) {
        this.client = client;
    }
}


@Entity
public class Vehicle implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String licenseNr;
    private boolean stolen;
    @OneToOne(targetEntity = Cartrack.class)
    private Cartrack cartrack;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    /**
     * @return the licenseNr
     */
    public String getLicenseNr() {
        return licenseNr;
    }

    /**
     * @param licenseNr the licenseNr to set
     */
    public void setLicenseNr(String licenseNr) {
        this.licenseNr = licenseNr;
    }

    /**
     * @return the stolen
     */
    public boolean isStolen() {
        return stolen;
    }

    /**
     * @param stolen the stolen to set
     */
    public void setStolen(boolean stolen) {
        this.stolen = stolen;
    }

    /**
     * @return the cartrack
     */
    public Cartrack getCartrack() {
        return cartrack;
    }

    /**
     * @param cartrack the cartrack to set
     */
    public void setCartrack(Cartrack cartrack) {
        this.cartrack = cartrack;
    }
}