Question

我有两个类策略和Acl。他们之间有很多关系。

//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>();
}

现在当我使用Cascade类型作为持久性时，我收到以下错误：

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

当我使用cascade类型作为all时，它会成功保存策略实体和acl实体。我无法理解这是怎么回事。注意：我只是执行保存操作。

这是主要代码：

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();
    }

Answer 1

使用session.persist()代替session.save()

有关详细信息，请参阅hibernate文档：

1）Session.persist():

使瞬态实例持久化。此操作级联到关联映射的关联实例的级联=＆＃34;坚持＆＃34;

2）Session.save():

保留给定的瞬态实例，首先分配生成的标识符。（或者使用标识符属性的当前值if 使用指定的生成器。）此操作级联到关联实例，如果关联映射为 cascade =＆＃34; save-update＆＃34;

hibernate - 级联类型持久存在多对多的关系

1 个答案: