實體管理器批量更新給出 org.hibernate.PersistentObjectException: detached entity傳遞給持久化

Question

我嘗試關注這篇文章，因為通過批量更新，我使用合並獲得了不必要的選擇：

for(int i = 0; i< elements.size(); i++){
    Query q = em.createQuery("select p from Parent p join fetch p.child c where p.id=:id", Parent.class);
    //parameter of :id from elements
    Parent p = q.getSingleResult();
    p.setName("aname"); //for simplicity just the name member
    myList.add(p);
}

utx = com.arjuna.ats.jta.UserTransaction.userTransaction();
utx.begin();
em.joinTransaction();

for(int i = 0; i< myList.size(); i++){
    if (i > 0 && i % Common.BATCH_SIZE == 0) { //BATCH_SIZE=50
        em.flush();
        em.clear();
    }
    Parent myObject = myList.get(i);
    em.merge(myObject);
}
utx.commit();

這是我的實體定義：

@Entity
@Table(name = "myparenttable", schema = "myschema", catalog = "mydb")
@JsonIgnoreProperties(ignoreUnknown = true)
public class Parent implements Serializable {
    private Integer id_parent;
    private String name;

    @JsonManagedReference
    @JsonInclude(JsonInclude.Include.NON_NULL)
    @JsonProperty(access = JsonProperty.Access.WRITE_ONLY)
    private List<Child> children;
    
    //getters and setters

    @JsonInclude(JsonInclude.Include.NON_NULL)
    @OneToMany(mappedBy = "parent", targetEntity = Child.class, fetch = FetchType.LAZY,cascade = {CascadeType.PERSIST, CascadeType.MERGE})
    public Set<Child> getChildren() {
        return this.children;
    }

    public void setChildren(Set<Child> children) {
        this.children = children;
    }
    
    
}

@Entity
@Table(name = "mychildtable", schema = "myschema", catalog = "mydb")
public class Child implements Serializable {
    private Integer id_child;
    private String description;
   

    @JsonBackReference
    private Parent parent;
    
    //getters and setters
    
}

在提到的文章之后，我像這樣更改了我的代碼：

utx = com.arjuna.ats.jta.UserTransaction.userTransaction();
utx.begin();
em.joinTransaction();

Session session = em.unwrap( Session.class );
for(int i = 0; i< myList.size(); i++){
    if (i > 0 && i % Common.BATCH_SIZE == 0) { //BATCH_SIZE=50
        em.flush(); 
        em.clear();
    }
    Parent myObject = elements.get(i);
    session.update(myObject);
}
utx.commit();

當列表小於 BATCH_SIZE (<50) 時，編輯正確，但是，flush 和 clear 語句是必要的，我收到此錯誤：

detached entity passed to persist: Child

我也試過：

session.flush();
session.clear();

有完全相同的錯誤。 有什么我想念的嗎？

Answer 1

您是否檢查過列表是否包含重復的對象？ 如果一批嘗試更新具有相同標識符的對象兩次，您可能會遇到此問題。