“传递给持久性错误的分离实体"带有 JPA/EJB 代码 [英] "detached entity passed to persist error" with JPA/EJB code

问题描述

我正在尝试运行这个基本的 JPA/EJB 代码:

I am trying to run this basic JPA/EJB code:

public static void main(String[] args){
         UserBean user = new UserBean();
         user.setId(1);
         user.setUserName("name1");
         user.setPassword("passwd1");
         em.persist(user);
  }

我收到此错误:

javax.ejb.EJBException: javax.persistence.PersistenceException: org.hibernate.PersistentObjectException: detached entity passed to persist: com.JPA.Database

有什么想法吗?

我在互联网上搜索，我发现的原因是:

I search on the internet and the reason I found was:

这是由您创建对象的方式引起的，即如果您显式设置了 ID 属性.删除 ID 分配修复了它.

This was caused by how you created the objects, i.e. If you set the ID property explicitly. Removing ID assignment fixed it.

但我没有明白，我需要修改什么才能使代码正常工作?

But I didn't get it, what will I have to modify to get the code working?

推荐答案

假设您有两个实体 Album 和 Photo.相册里有很多照片，所以是一对多的关系.

Let's say you have two entities Album and Photo. Album contains many photos, so it's a one to many relationship.

相册类

@Entity
public class Album {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    Integer albumId;

    String albumName;

    @OneToMany(targetEntity=Photo.class,mappedBy="album",cascade={CascadeType.ALL},orphanRemoval=true)
    Set<Photo> photos = new HashSet<Photo>();
}

照片类

@Entity
public class Photo{
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    Integer photo_id;

    String photoName;

    @ManyToOne(targetEntity=Album.class)
    @JoinColumn(name="album_id")
    Album album;

}

在persist或merge之前需要做的是在每张照片中设置相册引用.

What you have to do before persist or merge is to set the Album reference in each photos.

        Album myAlbum = new Album();
        Photo photo1 = new Photo();
        Photo photo2 = new Photo();

        photo1.setAlbum(myAlbum);
        photo2.setAlbum(myAlbum);       

这就是在持久化或合并之前如何附加相关实体.

That is how to attach the related entity before you persist or merge.

这篇关于“传递给持久性错误的分离实体"带有 JPA/EJB 代码的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！