LazyInitializationException 问题和正确设置 ManyToOne

如何解决LazyInitializationException 问题和正确设置 ManyToOne

我有 3 个像这样相互连接的对象：

@Entity
public class Room {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column
    private String name;

    @OnetoMany(mappedBy = "room",fetch = FetchType.EAGER)
    private List<SponsorStart> sponsoRSStart = new ArrayList<>();

    @OnetoMany(mappedBy = "room",fetch = FetchType.LAZY)
    private List<SponsorFinish> sponsorsFinish = new ArrayList<>();
    //getters and setters
    ```
@Entity
public class SponsorStart {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "room_id")
    private Room room;

    @OnetoMany(cascade = CascadeType.ALL)
    private List<Post> posts;
//getters and setters

@Entity
public class Post {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    @Column
    private long pk;
    @Column
    private String postId;
    //getters and setters

如果设置像 top 这样的设置，那么结果如下：

请注意，显示了 4 行（如果从 0 开始，则为 3 行） 但是，如果我想获取帖子表单 SponsorStart 对象的列表，我会得到：

org.hibernate.LazyInitializationException: Failed to lazily initialize a collection of role: com.spring.givestracker.model.SponsorStart.posts,Could not initialize proxy - no Session
        at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:597)
        at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:216)
        at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:576)
        at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:147)
        at org.hibernate.collection.internal.PersistentBag.iterator(PersistentBag.java:303)
        at com.spring.givestracker.service.impl.SponsorsFinishServiceImpl.parseSponsorFinishByRoom(SponsorsFinishServiceImpl.java:78)
Here is lazy:
    for (SponsorStart sponsorStart : room.getSponsoRSStart()) {
            Hibernate.initialize(sponsorStart.getPosts());
         }

好吧，我想我知道问题并在 SponsorStart 实体中添加：

    @OnetoMany(cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Post> posts;

但是！我有这个问题！

是的，这里有问题！我在 4 个 SonsorStart 实体中总共有 43 个帖子，为什么它会这样显示，我应该怎么做才能修复它？

帮助）

更新 1

@Entity
public class Room {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column
    private String name;

    @OnetoMany(mappedBy = "room",fetch = FetchType.EAGER,cascade = CascadeType.ALL)
    private List<SponsorStart> sponsoRSStart = new ArrayList<>();

    @OnetoMany(mappedBy = "room",fetch = FetchType.LAZY,cascade = CascadeType.ALL)
    private List<SponsorFinish> sponsorsFinish = new ArrayList<>();
    //getters and setters

@Entity
public class SponsorStart {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @ManyToOne (fetch=FetchType.LAZY,cascade=CascadeType.ALL)
    @JoinColumn(name = "room_id")
    private Room room;

     @OnetoMany(mappedBy = "sponsorStart",cascade = CascadeType.ALL)
    private List<Post> posts;
//getters and setters

@Entity
public class Post {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    @Column
    private long pk;
    @Column
    private String postId;
    @ManyToOne(fetch=FetchType.LAZY)
    private SponsorStart sponsorStart;

 //getters and setters

我面临着延迟初始化

org.hibernate.LazyInitializationException: Failed to lazily initialize a collection of role: com.spring.givestracker.model.SponsorStart.posts,Could not initialize proxy - no Session
        at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:597)
        at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:216)
        at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:576)
        at org.hibernate.collection.internal.AbstractPersistentCollection.forceInitialization(AbstractPersistentCollection.java:744)
        at org.hibernate.Hibernate.initialize(Hibernate.java:64)
        at com.spring.givestracker.service.impl.SponsorsFinishServiceImpl.parseSponsorFinishByRoom(SponsorsFinishServiceImpl.java:73)

解决方法

从 RoomController 使用 RoomService 我得到 findRoomById(id)，RoomService 有 @Transactional，并且从 RoomController 我给 Room 找到了另一个服务。当我委托另一个服务使用 RoomService 来 findRoomById(id) 时，Lazy 的问题就消失了！但是我不知道当我有 4 个赞助商但休眠加载我 43 次 4 个赞助商时是什么，因为赞助商获得 43 个帖子...