java - Hibernate - @OneToMany - 调用方法时发生 com.sun.jdi.InvocationException

Question

我对 OneToMany 关系有疑问。我正在使用 spring-mvc 和 spring-security 以及 hibernate 4。

我正在为所有人使用注释。

我的问题是在实体 War 中，当我看到属性列表播放器调试时，我看到 players= PersistentBag 并且当我单击它时 com.sun.jdi.InvocationException 发生调用方法。

我也得到了这个异常(exception):

org.apache.jasper.JasperException: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: clanwar.model.War.players, could not initialize proxy - no Session

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: clanwar.model.War.players, could not initialize proxy - no Session

实体:

@Entity
@Table(name = "WARS")
public class War implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "ID", nullable = false)
    private int id;

    @ManyToOne
    @JoinColumn(name = "CLAN")
    private Clan clan;

    @Column(name = "START_DATE")
    private Date startDate;

    @Column(name = "ENEMY_NAME")
    private String enemyName;

    @OneToMany(mappedBy = "war")
    private List<WarPlayer> players;

    @Transient
    private List<Enemy> enemies;

    public War() { }

    // Getters and setters.

}

--

@Entity
@Table(name = "WAR_PLAYERS")
public class WarPlayer implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @ManyToOne
    @JoinColumn(name = "WAR")
    private War war;

    @Id
    @ManyToOne
    @JoinColumn(name = "PLAYER")
    private Player player;

    @Column(name = "WAR_NUMBER")
    private int warNumber;

    @ManyToOne
    @JoinColumn(name = "OBJETIVE_1")
    private Attack objetive1;

    @ManyToOne
    @JoinColumn(name = "OBJETIVE_2")
    private Attack objetive2;

    @ManyToOne
    @JoinColumn(name = "RECOMMENDED_1")
    private Attack recommended1;

    @ManyToOne
    @JoinColumn(name = "RECOMMENDED_2")
    private Attack recommended2;

    @ManyToOne
    @JoinColumn(name = "FINAL_1")
    private Attack final1;

    @ManyToOne
    @JoinColumn(name = "FINAL_2")
    private Attack final2;
    private String comment;

    public WarPlayer() {}

    // Getters and setters

}

我的道

@Override
    public War findById(int id) throws DaoException {

        War war;

        try {
            war = (War) getSession()
                    .createQuery("from War where ID = :id")
                    .setParameter("id", id)
                    .uniqueResult();
        } catch (Exception e) {
            throw new DaoException(e.getMessage());
        }

        return war;
    }

Answer 1

Hibernate 文档说:

In the normal case the orders association would be lazy loaded by Hibernate

所以，你需要使用预取:

 @OneToMany(mappedBy = "war",fetch = FetchType.EAGER)
 private List<WarPlayer> players;