I have two threads one of them write text field to the database, another try to read this field but it can`t.
field has following anatation:
#Lob
#Column(name = "response_soap")
#Basic(fetch = FetchType.LAZY)
public String getResponseSoap() {
return responseSoap;
}
Both thread it's part of the web application. Both running on the same weblogic server.
All transaction is commited. There is field in the database.
Every time I'm creating new Entity manager.
What error do you get?
Try using a refresh, em.refresh(object)
Are you serializing the object? Since it is LAZY it will be null when you serialize it, unless you access before you serialize it. Try making it EAGER.
I believe that only
Many-to_many and One-to-many are can be set to lazyload
One-to-one, Many-to-one and Basic are all Egar
http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Basic_Mappings/Lazy_Basics
Related
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'm retrieving list of objects from database using JPA repository.
If I don't access sub classes in any way, they will be null.
If I just go and show count of them in log file, they will not be null.
I'm not sure why is this happening.
In below code, if I comment out 'for loop', policy.getFields() and policy.getFieldGroups will be null.
Why is this happening?
log.debug("Request to get all Policies");
List<Policy> policies = policyRepository.findAll();
for (Policy policy : policies) {
log.info("Policy fields group size:{}", policy.getFieldGroups().size());
log.info("Policy fields size:{}", policy.getFields().size());
}
return policies;
This is called lazy loading (or lazy initialization) , which means that collection relations will be fetched when they are about to be used. This is perfectly normal behavior. If you need it everytime, you can change loading of that relation to EAGER so those will be fetched everytime.
This can be done by adding #OneToMany(fetch = FetchType.EAGER) on fields you are need to be loaded (here field groups and fields)
I have a Visit entity which refers to a Patient entity by ManyToOne relationship. The repository for Visit is:
#RepositoryRestResource(collectionResourceRel = "visits", path = "visits", excerptProjection=VisitProjection.class)
public interface VisitRepository extends PagingAndSortingRepository<Visit, Long> {
#RestResource(path="all")
List<Visit> findByPatientIdContaining(#Param("keyword") String keyword);
}
When searching visits by patient ID with /visits/search/all?keyword=1 which may return millions of records, the query is forever pending and never ends. In the console there are dozens of hibernate sqls printed every second. How can I set the request timeout from server side?
I have tried:
And Transactional annotation with timeout attribute to repository method: (works a little but still takes long to timeout)
#RestResource(path="all")
#Transactional(timeout=2)
List<Visit> findByPatientIdContaining(#Param("keyword") String keyword);
add some timeout properties to application.properties: (just doesn't work at all):
spring.jpa.properties.hibernate.c3p0.timeout=2
spring.jpa.properties.javax.persistence.query.timeout=2
spring.mvc.async.request-timeout=2
server.connection-timeout=2
rest.connection.connection-request-timeout=2
rest.connection.connect-timeout=2
rest.connection.read-timeout=2
server.servlet.session.timeout=2
spring.session.timeout=2
spring.jdbc.template.query-timeout=2
spring.transaction.default-timeout=2
spring.jpa.properties.javax.persistence.query.timeout=2
javax.persistence.query.timeout=2
server.tomcat.connection-timeout=5
Okay, no one using your API is going to want millions of records in one hit so use the provided paging functionality to make the result set more manageable:
https://docs.spring.io/spring-data/rest/docs/3.1.6.RELEASE/reference/html/#paging-and-sorting
#RestResource(path="all")
Page<Visit> findByPatientIdContaining(#Param("keyword") String keyword, Pageable p);
Clients can specify the records they want the records returned by adding the params:
?page=1&size=5
I am using rest services with spring data . when i get data from single table its return proper result in json format . but when i use many to many association between entities using hibernate i am getting an un acceptable result with following error in chrome's console .
Failed to load resource: net::ERR_INCOMPLETE_CHUNKED_ENCODING
My result looks like there just one row repeating itself , and its a particularly that field which is being used in new generated table by association.
[{"id":7,"name":"Milk pack","description":"haleeb","imageUrl":"milk.jpg","price":350.00,"category":null,"orderDetail":[]},{"id":8,"name":"oil","description":"olive oil ","imageUrl":"/resources/uploads/olive.png","price":670.00,"category":null,"orderDetail":[{"id":263,"productlist":[{"id":10,"name":"Mobile","description":"awesome design, slim design ","imageUrl":"/static/uploads","price":34569.00,"category":null,"orderDetail":[{"id":263,"productlist":[{"id":10,"name":"Mobile","description":"awesome design, slim design ","imageUrl":"/static/uploads","price":34569.00,"category":null,"orderDetail":[{"id":263,"productlist":[{"id":10,"name":"Mobile","description":"awesome design, slim design ","imageUrl":"/static/uploads","price":34569.00,"category":null,"orderDetail":[{"id":263,"productlist":[{"id":10,"name":"Mobile","description":"awesome design, slim design
.
.
.and so on
My entities are following
Product table
#ManyToMany(mappedBy = "productlist")
private List<OrderDetail> orderDetail =new ArrayList<OrderDetail>();
OrderDetail table
#ManyToMany
#JoinTable(
name="order_detail_productlist",
joinColumns=#JoinColumn(name="order_detail_id", referencedColumnName="id"),
inverseJoinColumns=#JoinColumn(name="productlist_id", referencedColumnName="id"))
private Set<Product> productlist = new HashSet<Product>();
I am using spring data jpa repository to get them
List<Product> findAll();
Note: which products those are not ordered yet that are working properly
You need the all log for the information, it maybe cause by loop when with jackson. So you need add #JsonIgnoreProperties.Please see http://stackoverflow.com/questions/3325387
My Problem is solved by using jackson 2.0 documentation
by Adding following annotation or OrderDetail table
#JsonBackReference
it breaks loop and show result properly
Is it possible to somehow get multiple objects from a one-to-many-collection by index/key, which is marked with extra lazy load?
I have a big collection where I can't fetch all entries but still want to get multiple objects from it.
For example:
class System
{
...
#OneToMany(mappedBy = "system")
#MapKey(name = "username")
#LazyCollection(LazyCollectionOption.EXTRA)
private Map<String, User> users = new HashMap<>();
public List<User> getUsers(List<String> usernames)
{
//what to do
}
}
It's just a simple example but it portraits my problem.
I know I could just use the Criteria API or (named) queries but I try to keep the logic where it belongs to.
Unfortunately it seems that Hibernate does not support loading multiple entries from a collection inside a entity.
Only ways I found:
use eager/lazy loading and get all objects (which won't work if there are many)
use extra lazy loading and get multiple objects by retrieving one by one (can hurt performance)
use Session.createFilter which can not be called inside an entity