Hibernate / JPA使用生成的UUID持久保存OneToMany对象

Question

I have been using Hibernate a lot but using Hibernate/JPA with UUID got me stumped a bit. I am using hibernate 5.2.12.Final.

I have an object called TimePeriod with this mapping:

@Entity(name = "time_period")    
public class TimePeriod extends AbstractDomainObject {

   @OneToMany(mappedBy = "timePeriod", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
   private List<TimePeriodBlock> timePeriodBlocks = new ArrayList<>();
   ...
   public void addTimePeriodBlock(TimePeriodBlock timePeriodBlock) {
      timePeriodBlock.setTimePeriod(this);
      this.timePeriodBlocks.add(timePeriodBlock);
   }
   ...

With the following child relationship:

@Entity(name = "time_period_block")
public class TimePeriodBlock extends AbstractDomainObject {
   ...   
   @ManyToOne
   @JoinColumn(name = "time_period_id", nullable = false)
   private TimePeriod timePeriod;
   ...

They share this super class:

@MappedSuperclass
public abstract class AbstractDomainObject {
   ...
   @Id
   @GeneratedValue
   @Column(name = "id", columnDefinition = "uuid", updatable = false)
   private UUID id;
   ...

When I execute the following:

// pseudo code
TimePeriod t = new TimePeriod();
t.setName("test");
TimePeriodBlock b = new TimePeriodBlock();
t.addTimePeriodBlock(b);

em.persist(t);

I get the exception:

...
Caused by: org.hibernate.PropertyValueException: not-null property references a null or transient value : test.TimePeriodBlock.timePeriod
...

Some notes:

I strongly believe that this could be because Hibernate generates the UUID (and not the database) but, since I am not sure, I hope some fellow Developer might know how this could work.

I am using PostgreSQL 9.6 and the database can also generates UUIDv4 but requires compiling an extra extension so I opted for Hibernate to generate it.

When I enter some data in the database and retrieve the data it is fetched without any error.

Storing other objects without @ManyToOne relationships do store without any error and have a UUID that is generated by Hibernate.

Answer 1

Well after some debugging and using Luay Abdulreheem suggestion I found out that hibernate is working just fine; in this case my objects are send using a REST interface (using Jackson) and the reference to the parent was lost as the unmarshalling of the JSON is done using fields.

So nothing to see here, move along...