LazyInitializationException 问题和正确设置 ManyToOne

Question

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

如果设置类似 top 的设置，则结果如下：请注意显示了 4 行（如果从 0 开始则为 3 行）但是，如果我想从 SponsorStart 对象中获取 post 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());
         }

好的，我以为我知道问题并在 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，这是问题！我在 4 个 SonsorStart 实体中总共有 43 个 post，为什么它会这样显示，我应该如何修复它？

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

而且我面临延迟初始化

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)

Answer 1

从使用 RoomService 的 RoomController 中，我得到 findRoomById(id)，RoomService 具有@Transactional，从 RoomController 中，我将 Room was found 给另一个服务。当我委托另一个服务使用 RoomService 来查找 RoomById(id) 时，Lazy 的问题消失了！但是我不知道当我有 4 个赞助商但休眠加载我 43 次 4 个赞助商时那是什么）因为赞助商获得 43 个帖子...

LazyInitializationException 问题和正确设置 ManyToOne

Problem with LazyInitializationException and Correct setting ManyToOne

java

postgresql

spring-mvc

lazy-initialization