Question

我有以下课程：

@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);
    }
}

我的交易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，我正在做以下事情：

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

上收到以下例外情况

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 Console Application？

我知道我可以使用连接HQL查询或使其成为Eager，但我想让它懒得用于自学习目的：）

Answer 1

String playerId = daoService.addPlayer（player）; 在上面的代码中，您保存实体并在当前会话关闭。之后，您尝试使用相同的会话加载玩家。但是没有开放会话。你必须在getPlayer方法中打开新会话，

您的代码应该更改为

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

控制台应用程序中的延迟加载错误

1 个答案: