Question

我正在使用Glassfish 3.1.2和集成的EclipseLink JPA实现。我的问题是特定父级的子对象并不总是被加载（有时它是，有时它不是）。我也在使用Jax-RS和Jax-b。我也使用SQLite作为数据库。奇怪的是，如果我重新启动glassfish（几次），或者几次刷新我的页面，一切都正常加载。

@Entity
@XmlRootElement
public class Location {

    @Id
    @GeneratedValue(strategy=GenerationType.TABLE)
    private int id;
    @NotNull
    private String name;
    @NotNull
    private String lat;
    @NotNull
    private String lon;

    @ManyToOne
    @NotNull
    private User user;

    @ManyToOne
    @NotNull
    private Beer beer;
    // getters & setters

@Entity
@XmlRootElement
public class Beer {

    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    private int id;
    @NotNull
    private String name;
    @NotNull
    private String description;
    @NotNull
    private Date added;
    @NotNull
    private String pic;

    private int rateAroma; // type1
    private int rateAlcoholContent; // type2
    private int rateFlavour; // type3

    @OneToMany(mappedBy = "beer")
    private Collection<Comment> comments;

    @OneToMany(mappedBy = "beer")
    private Collection<Rate> ratings;

    @OneToMany(mappedBy = "beer")
    private Collection<Location> locations;

    @ManyToMany
    @JoinTable(joinColumns = @JoinColumn(name = "BEER_ID", referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name = "USER_ID", referencedColumnName = "id"))
    private Collection<User> users;

    // I've only included get/set methods of attributes which are marked @XmlTransient

    @XmlTransient
    public Collection<Comment> getComments() {
    return comments;
    }

    @XmlJavaTypeAdapter(SqlDateAdapter.class)
    public Date getAdded() {
    return added;
    }

    @XmlTransient
    public Collection<Rate> getRatings() {
    return ratings;
    }

    @XmlTransient
    public Collection<Location> getLocations() {
    return locations;
    }

    @XmlTransient
    public Collection<User> getUsers() {
    return users;
    }

REST服务

@GET
@Path("/beers/{id}")
@Produces(MediaType.APPLICATION_JSON)
public List<Location> getMarkedLocations(@PathParam("id") int locationId) {
    String locationName = null;
    try {
        locationName = locdao.getLocation(locationId).getName();
    } catch (Exception e) {
        System.out.println("no such location");
        return null;
    }
    List<Location> locations = locdao.getLocationsAndBeers(locationName);
    return locations;
}

LocationDAO

public List<Location> getLocationsAndBeers(String param) {
    em = DB.getDBFactory().createEntityManager();
    List<Location> locations = null;
    try {
        Query q = em.createQuery("SELECT l FROM Location l WHERE l.name = :name",     Location.class);
        q.setParameter("name",param);
        locations = (List<Location>)q.getResultList();
    } catch (Exception e) {
        System.out.println(e.toString());
    } finally {
        em.close();
    }
    return locations;
}

数据库

 ID LOCATION_NAME       BEER_ID USER_ID
 10 location name       3       1
 11 location name       4       2
 60 location name      53      51
 61 location name      54      52
 62 beer bar            3       1

我要做的是从数据库获取所有位置，这些位置与我在url中传递的id的位置相同。我尝试使用INNER JOINS，LEFT JOINS，LEFT JOINS FETCH等来操纵我的SQL，但问题仍然存在。

这是我应该得到的JSON如果位置ID是61

{"location":{"beer":{"added":"2013-04-29 18:17:39","description":"DESC","id":"3","name":"beer_name","pic":"url b1","rateAlcoholContent":"3","rateAroma":"4","rateFlavour":"3"},"id":"62","name":"beer bar","user":{"email":"u1@email","fbid":"0","id":"1","lastName":"lastname u1","name":"name u1","username":"u1"}}}

我有时会得到什么。没有啤酒对象。

{"location":{"id":"62","name":"beer bar","user":{"email":"u1@email","fbid":"0","id":"1","lastName":"lastname u1","name":"name u1","username":"u1"}}}

JPA（EclipseLink 2.4）并不总是加载子对象

0 个答案: