[英]Why the Cascading persist does not work with many-to-many relationship in Hibernate?
[英]hibernate - cascading type persist for many to many relationship
我有兩個類策略和Acl。 他們之間有一個ManyToMany關系。
//政策
public class PolicyEntity {
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE)
@Column(name = "POLICY_ID")
private int policyId;
@Column(name = "POLICY_NAME")
private String policyName;
@ManyToMany(cascade = CascadeType.PERSIST)
@JoinTable(name = "POLICY_ACL",joinColumns=@JoinColumn(name = "POLICY_ID"),
inverseJoinColumns=@JoinColumn(name = "ACL_ID"))
private List<AclEntity> aclList = new ArrayList<AclEntity>();
}
// Acl
public class AclEntity {
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE)
@Column(name = "ACL_ID")
private int aclId;
@Column(name = "ACL_NAME")
private String aclName;
@ManyToMany(mappedBy = "aclList")
private List<PolicyEntity> policyList = new ArrayList<PolicyEntity>();
}
現在,當我使用Cascade類型作為持久性時,我得到以下錯誤:
Hibernate: insert into POLICY (POLICY_NAME, POLICY_ID) values (?, ?)
Hibernate: insert into POLICY_ACL (POLICY_ID, ACL_ID) values (?, ?)
Exception in thread "main" org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: hibernate.AclEntity
而當我使用cascade類型作為all時,它會成功保存策略實體和acl實體。我無法理解這是怎么回事。 注意:我只是執行保存操作。
這是主要代碼:
public static void main(String[] args) {
PolicyEntity policyEntity = new PolicyEntity();
AclEntity aclEntity = new AclEntity();
//policyEntity.setPolicyId(1);
policyEntity.setPolicyName("Policy 3");
//aclEntity.setAclId(1);
aclEntity.setAclName("Acl 3");
policyEntity.getAclList().add(aclEntity);
Configuration configuration = new Configuration().configure();
StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder().
applySettings(configuration.getProperties());
SessionFactory sessionFactory = configuration.buildSessionFactory(builder.build());
Session session = sessionFactory.openSession();
session.beginTransaction();
session.save(policyEntity);
session.getTransaction().commit();
session.close();
}
使用session.persist()
而不是session.save()
有關詳細信息,請參閱hibernate文檔:
使瞬態實例持久化。 如果使用cascade =“persist”映射關聯,則此操作會級聯到關聯的實例
保留給定的瞬態實例,首先分配生成的標識符。 (或者,如果使用指定的生成器,則使用identifier屬性的當前值。)如果使用cascade =“save-update”映射關聯,則此操作會級聯到關聯的實例
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.