远程访问Jpa实体

Question

I'm currently working on system that consists of Java Web app and C# client app. Web app has Java Web Service, which has method that returns entity object of Program class:

@WebMethod(operationName = "getProgram")
public Program getProgram(@WebParam(name = "macAddress") String macAddress){
    Device device = DeviceManager.getInstance().getDevice(macAddress);
    if(device != null){
        return device.getProgram();
    }
    return null;
}

This return object of type Program which has many properties and relations:

@Entity
@Table(name = "PROGRAM", schema = "APP")
@XmlRootElement
@NamedQueries({
@NamedQuery(name = "Program.getProgramsByWeather", query = "SELECT p FROM Program p WHERE p.weather = :weather")})
public class Program extends DbEntity implements Serializable {

    private static final long serialVersionUID = 1L;
    @JoinColumn(name = "LOGO_ID", referencedColumnName = "ID")
    @OneToOne(cascade = CascadeType.ALL, orphanRemoval = true, fetch= FetchType.EAGER)
    private Logo logo;
    @JoinColumn(name = "WEATHER_ID", referencedColumnName = "ID")
    @ManyToOne
    private Weather weather;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "program", orphanRemoval = true)
    private List<ProgramPlaylist> programPlaylistList = new ArrayList<>();
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "program", orphanRemoval = true)
    private List<ProgramTicker> programTickerList = new ArrayList<>();
    @Column(name = "UPDATED")
    private boolean updated;

    public Program() {
    }

    public Program(String name, AppUser owner) {
        super(name, owner);
    }

    public Logo getLogo() {
        return logo;
    }

    public void setLogo(Logo logo) {
        this.logo = logo;
    }

    public Weather getWeather() {
        return weather;
    }

    public void setWeather(Weather weather) {
        this.weather = weather;
    }

    public boolean isUpdated() {
        return updated;
    }

    public void setUpdated(boolean updated) {
        this.updated = updated;
    }

    @XmlElement
    public List<ProgramPlaylist> getProgramPlaylistList() {
        return programPlaylistList;
    }

    @XmlElement
    public List<ProgramTicker> getProgramTickerList() {
        return programTickerList;
    }

    @Override
    public String toString() {
        return "Program[ id=" + getId() + " ]";
    }
}

Client can get this object and accessing some properties in client app like program.name, which it inherits from DbEntity , but when i try to call something like this:

program.logo.name

client throws NullReferenceException. Same exception occurs when i try to iterate over the elements of programPlaylistList ArrayList.

I'm assuming that the object itself that is passed through to client isn't fully loaded.

How can i solve this problem, please help?!

EDIT Ok, so I printed out XML response that client get from service and its populated correctly, but for some reason object fields aren't populated and are mostly null. Why is this occurring?

Answer 1

默认情况下，@OneToMany批注的获取策略为LAZY ，是否尝试过像@oneToOne字段中那样将其指定给EAGER（fetch = FetchType.EAGER）？