I have an entity Product which have many fields and associations (around 60).
And a table ProductView which has a #ManyToOne(fetch = FetchType.LAZY) association with Product.
Is there a optimal way to retrieve Product object and assign it to ProductView ?
If its used JPA findById(productId) or JPQL/EntityManager selects-> It will retrieve all products fields and associations
Product product = productRepository.findById(productId);
ProductView productView = new ProductView(product);
save(productView);
If its used JPA getOne -> It solves the problem but the Proxy can throw error if Product does not exists. And this error can not be handled because it happens at runtime.
Product product = productRepository.getOne(productId);
ProductView productView = new ProductView(product);
save(productView);
If a DTO is used or Interface which refers to the same Product Table -> We will get just an object with Id field, but a lot more processes will need to be added (Which I am not familiar with)
Delete foreign keys from ProductView table (#ManyToOne -> #Column) and simple assign productIds. But in this way, there will be no logic connection between tables.
ProductView DB
How usually developers avoid this problem ?
I don't understand what the problem is. Just use getOne approach and at the end of your method, use flush which will throw the constraint violation exception that you can handle. This is the way to go.
I want a many-to-many relationship between an entity table and a join table. Invoices consist of a set of subscriptions. A subscription can be a part of multiple invoices (e.g. monthly subscription). Subscriptions consist of a user and a service. I am already using the subscriptions table as a join table for the many-to-many relationship between users and services (e.g. a user can subscribe to multiple services and a single service has multiple users). I have a table, "invoice_subscription," with IDs for both the invoice and subscription. Every table has its own ID. Below is the relevant snippet in the invoice object:
#ManyToMany
#JoinTable(
name = "invoice_subscription",
joinColumns = #JoinColumn(name = "invoice_id"),
inverseJoinColumns = #JoinColumn(name = "subscription_id")
)
public Set<Subscription> getSubscriptions() {
return subscriptions;
}
I am using the following in the subscription object:
#ManyToMany(mappedBy = "subscriptions")
public Set<Invoice> getInvoices() {
return invoices;
}
For the above, I am receiving the error below:
org.hibernate.MappingException: Foreign key (FKfe5yu82iapjynsdyfitclkri4:invoice_subscription [subscription_id])) must have same number of columns as the referenced primary key (subscription [user_id,service_id])
When I switch to two "#JoinColumn" annotations with the IDs in the error, I get the following error:
org.hibernate.AnnotationException: A Foreign key refering com.example.model.Subscription from com.example.model.Invoice has the wrong number of column. should be 1
I agree with this, but it seems to contradict the previous error. I've read documentation, guides, and other questions, but I have not found any useful information. I'm clearly missing something obvious.
I am a newbie to Java Persistence API and Hibernate and using Spring JPA repositories for querying in DB. Now I have two entities in Parent <-> Child relationship with Parent entity with #OneToMany and Child entity with #ManyToOne mapping.
Parent Entity:-
#Entity
#Table(name = "PERSONS")
public class Persons {
...
#OneToMany(mappedBy = "person", cascade = CascadeType.ALL, fetch = FetchType.LAZY, orphanRemoval = true)
public List<Cards> cards = new ArrayList<Cards>();
...
}
Child Entity:-
#Entity
#Table(name = "CARDS")
public class Cards {
...
#ToString.Exclude
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "PERSON_ID", nullable = false, insertable = false, updatable = false)
public Person person;
...
}
And I am using my PersonsRepository like below :-
#Repository
public interface PersonsRepository extends JpaRepository<Persons, String> {
....
}
Now the fetchType being used in the relationship is LAZY at both the ends. Now whenever I tried to loop over a List and tried to process the cards for each using person.getCards(), it gives me below error:-
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.xxx.abc.Persons.cards, could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:606)
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:218)
at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585)
at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149)
at org.hibernate.collection.internal.PersistentSet.iterator(PersistentSet.java:188)
at java.util.Spliterators$IteratorSpliterator.estimateSize(Spliterators.java:1821)
at java.util.Spliterator.getExactSizeIfKnown(Spliterator.java:408)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
Now I have found everyone saying that using LAZY is the best approach in Hibernate and it says lot more about the correct design of code as well. I agree the way I have used person.getCards() will not have any open session and that is the reason it is giving me LazyInitializationException but the intent behind this is to save a lot more DB calls.
Assuming I have 1000 persons list, that means I have to make 1000 separate calls to getCards() for each person. That's why if I use the FETCHTYPE.EAGER in Person #OneToMany, what is the performance impact since everything will be fetched eagerly.
Need suggestions about the best practices followed for such kind of problems. TIA.
Edit:-
I have a method in service class where I am using #transactional for that like below:-
#Transactional(readOnly = true)
public void fetchData(Integer param1, Timestamp param2, Timestamp param3, List<String> param4, NavigableMap<Long, List<Cards>> param5) {
List<Persons> validPersons = personRepo.getCardsPerPerson(param2, param3);
if(validPersons != null && !validPersons.isEmpty()) {
// store the cards on the basis of epoch timestamp
prepareTimestampVsCardsMap(validPersons, param4, param5);
}
}
private void prepareTimestampVsCardsMap(List<Persons> validPersons, List<String> uList, NavigableMap<Long, List<Cards>> timestampVsCardsList) {
for(Person person : validPersons) {
Long epoch = order.getOrderTime().getTime();
Set<Cards> cardsPerPerson = person.getCards();
}
}
Also, the query being used in repository for getting the cards associated to a person is using join fetch as below:-
#Query(value = "select p from Person p join fetch Cards c on p.id = c.id WHERE p.orderTime BETWEEN ?1 AND ?2 ORDER BY orderTime ASC")
public List<Person> getCardsPerPerson(Timestamp param1, Timestamp param2);
I am still getting the same above mentioned LazyInitializationException. Can anyone please help.
First of all, it's always better to use FetchType.LAZY instead of FetchType.EAGER. Why? Because you might not need all the data every time. If you want to return a list of Persons and display them somehow, somewhere, do you need to fetch all of their cards as well? If not, then FetchType.LAZY would be the better option, and you would then control how much data you need.
LazyInitializationException usually indicates that you didn't fetch all the data you need while your Session was opened. There are many ways to fetch associated data (none of which is keeping the Session opened while processing request):
1. using join fetch in your JPQL/HQL
#Query("select p from Person p join fetch p.cards where ...")
List<Person> getCardsPerPerson(Timestamp param1, Timestamp param2);
2. if you're using Spring Data, you could use #EntityGraph instead of join fetch
#EntityGraph(attributePaths = { "cards" })
List<Person> getPersons();
That way, every time you call getPersons, it will fetch cards as well. Of course, you couldn't use this one if you have to write #Query.
If you're using Spring Data's naming conventions for some simple queries, then #EntityGraph would be an option for fetching associations.
3. using Criteria API
Again, if you're using Spring Data, this is just a fallback solution in case you end up with MultipleBagFetchException. I will not go into details for this one, but in case you encounter this exception, you'll find solution in Vlad Mihalcea's blog post The best way to fix the Hibernate MultipleBagFetchException.
You are under the misconception that EAGER loading means Hibernate will fetch all data with one statement, this is false. With EAGER as a strategy, the framework will just do every query required to fetch all data for every entity.
Example: If one entity has 2 EAGER relationships, fetching one will result in 3 statements, one to load the entity, one for each of its relationships. If you have 3 entities, you will have 7 statements, the initial statement loading the 3 objects, plus 2 per object.
When your treatment requires everything, there is no real performance impact at the moment. But most applications are not made of one treatment. This means every treatment in your application will load everything which is EAGER, even if not needed. This will effectively slow everything down. You also risk loading all your database in memory if everything is in EAGER.
This is why LAZY is the recommended approach.
As for your LazyInitializationException, it seems in your stack trace that you are using the stream API. It's a wild guess due to missing details, but JPA/Hibernate doesn't handle sharing a session between threads, so if you are using parrallelStream it could cause the problem.
I have a form changeed the properties of my object CUSTOMER. Each customer has related ORDERS. The ORDER's table has a column customer_id which is used for the mapping. All works so far, I can read customers without any problem.
When I now e.g. change the name of the CUSTOMER in the form (which does NOT show the orders), after saving the name is updated, but all relations in the ORDERS table are set to NULL (the customer_id for the items is set to NULL.
How can I keep the relationship working?
THX
UPDATE: Mapping Info
The Orders are mapped on the Customer side
#OneToMany
#JoinColumn(name = "customer_id")
#OrderBy("orderDate")
private Collection<Order> orders = new LinkedList<Order>();
UPDATE
Seems like adding a
#SessionAttributes("customer")
to my model, changing the method to
public String saveTrip(#ModelAttribute("customer") Customer customer, BindingResult result, SessionStatus status) {
if (!result.hasErrors()) {
this.tripManager.saveTrip(trip);
}
else {
logger.debug("Form data included errors, did not save data");
BindingUtils.logBindingErrors(result, logger);
}
status.setComplete();
return "redirect:/customers/";
}
Could solve the issu. But is this a good way of solving it???
One way would be not to submit the CUSTOMER Object from the form.
Instead submit the customer, submit only the customers ID and the new Name. In the controller you have to load the Customer by the submitted ID and then update the Name. And persist the Customer again.
HI,
Make cascade="none" attribute of many-to-one relationship from order side.
Thanks.
I have 2 tables, ENQUIRY and ELEMENT with a One-to-Many relationship such that an Enquiry has many Elements.
I would like to enforce Oracle's NOT NULL constraint on foreign key column ELEMENT.ENQUIRY_ID as this is best-practice. I have the following collection on the Enquiry object:
#OneToMany(cascade = CascadeType.ALL)
#JoinColumn(name = "ENQUIRY_ID", referencedColumnName = "ID")
private Set<Element> elements = new HashSet<Element>();
When I enforce the NOT NULL constraint I receive the following stacktrace:
Caused by: java.sql.BatchUpdateException: ORA-01400: cannot insert NULL into ("ELEMENT"."ENQUIRY_ID")
So Hibernate is obviously persisting the collection of elements before the parent enquiry and then going back and doing an UPDATE on the foreign key field afterwards.
Is there a way to enforce the NOT NULL constraint on the collection foreign key field?
Have you tried nullable = false in #JoinColumn?