java - 控制台应用程序中出现延迟加载错误

Question

我有以下类(class):

@Entity
@Table(name="Player")
public class Player {

    private String id;
    private Set<String> nicknames = new HashSet<String>();

        @ElementCollection(fetch=FetchType.LAZY)
    @CollectionTable(name="Nicknames", joinColumns=@JoinColumn(name="user_id"))
    @Column(name="nickname")
    public Set<String> getNicknames() {
        return nicknames;
    }
}

我的 DaoServiceImpl 看起来像这样:

@Repository("daoService")
public class DaoServiceImpl implements DaoService {

    @Autowired
    SessionFactory sessionFactory;

    @Override
    public String addPlayer(Player player){
        Session session = sessionFactory.getCurrentSession();
        return (String) session.save(player);
    }

    @Override
    public Player getPlayer(String id){
        Session session = sessionFactory.getCurrentSession();
        return (Player)session.load(Player.class, id);
    }

    @Override
    public void updatePlayer(Player player){
        Session session = sessionFactory.getCurrentSession();
        session.update(player);
    }
}

我的事务管理器看起来像这样:

<aop:config>
    <aop:pointcut id="daoServicePoint" 
            expression="execution(* com.vanilla.daoService.DaoService.*(..))"/>
    <aop:advisor advice-ref="txAdvice" pointcut-ref="daoServicePoint"/>
  </aop:config>

  <tx:advice id="txAdvice" transaction-manager="transactionManager">
    <tx:attributes>
      <tx:method name="add*" propagation="REQUIRED"/>
       <tx:method name="update*" propagation="REQUIRED"/>
      <tx:method name="get*" propagation="SUPPORTS" read-only="true"/>
    </tx:attributes>
  </tx:advice>

在我的主要功能中，我正在执行以下操作:

public void run(){
Player player = new Player();
player.addNickName("Nick1");
player.addNickName("Nick2");
player.setFirstName("Danny");
player.setLastName("Lesnik");
String playerId = daoService.addPlayer(player);
player = daoService.getPlayer(playerId);
player.addNickName("Nick4");
player.removeNickName("Nick2");
daoService.updatePlayer(player);
}

我在 player.addNickName 上遇到以下异常

Exception in thread "main" org.hibernate.LazyInitializationException: could not initialize proxy - no Session
    at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:167)
    at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:215)
    at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:190)
    at com.vanilla.objects.Player_$$_javassist_0.addNickName(Player_$$_javassist_0.java)
    at com.vanilla.main.Main.run(Main.java:27)
    at com.vanilla.main.Main.main(Main.java:36)

如果是Web应用程序，我会使用OpenSessionIviewFilter。我应该如何解决 Spring Hibernate Java 控制台应用程序？

我知道我可以使用 join HQL 查询或使其成为 Eager，但我想出于 self 学习的目的而让它变得懒惰:)

Answer 1

字符串playerId = daoService.addPlayer(player);在上面的代码中，您保存实体并在当前 session 关闭。之后，您尝试使用同一 session 加载玩家。但是没有打开的 session 。您必须在 getPlayer 方法中打开新 session ，

您的代码应更改如下

公共(public)玩家 getPlayer(String id){ session session = sessionFactory.openSession(); return (Player)session.load(Player.class, id); }