[e-mail].发生异常的调用方法

Question

我有一个问题与OneTo多关系。我正在使用sping-mvc和sping-Security和Hibernate4。

我正在为所有人使用注释。

我的问题是在实体战争中，当我看到属性列表玩家调试时，我看到玩家= PersistentBag，当我单击它时，com.sun.jdi.InvocationException发生了调用方法。

我也得到了这个例外：

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DAO

@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

替换我的道

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

    Transaction transaction = null;
    Session session = null;

    try {
        session = sessionFactory.openSession();
        session.setFlushMode(FlushMode.COMMIT);
        transaction = session.beginTransaction();

        String hql = "from War where ID = :id";
        Query query = session.createQuery(hql);

                query.setParameter("id", id).uniqueResult();

    } catch (Exception e) {
        throw new DaoException(e.getMessage());
    }

    return war;
}

Answer 2

FetchType.EAGER 效率不高。您必须包含 org.hibernate.annotations.Fetch 注释。

所以:

@Fetch(FetchMode.SUBSELECT)
@OneToMany(mappedBy = "war", fetch = FetchType.LAZY)
private List<WarPlayer> players;

Answer 3

Hibernate文档 说：

在正常情况下，订单关联将由Hibernate延迟加载

因此，您需要使用急切抓取:

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