Java Community | Help. Code. Learn.•3y ago

Spring JPA

JPA problem:

@Entity @Setter @Getter @NoArgsConstructor
public class BicycleRider {
    @Id
    @GeneratedValue (strategy = GenerationType.IDENTITY)
    private int id;
    // timeInSeconds refers to the amount of time it took finish the three stages of the race represented in seconds.
    private double timeInSeconds;
    private int mountainPoints;
    private int sprintPoints;
    @ManyToOne (fetch = FetchType.LAZY)
    @JoinColumn(name = "bicycleteam_id")
    private BicycleTeam bicycleTeam;
}

@Entity @Setter @Getter @NoArgsConstructor
public class BicycleRider {
    @Id
    @GeneratedValue (strategy = GenerationType.IDENTITY)
    private int id;
    // timeInSeconds refers to the amount of time it took finish the three stages of the race represented in seconds.
    private double timeInSeconds;
    private int mountainPoints;
    private int sprintPoints;
    @ManyToOne (fetch = FetchType.LAZY)
    @JoinColumn(name = "bicycleteam_id")
    private BicycleTeam bicycleTeam;
}

I want to create a BicycleRiderobject and store it i my database; however, I need a BicycleTeam to associate it to. Do I need to need to create a BicycleTeamobject or do I need to do something else?

19 Replies

JavaBot•3y ago

Hey, @Danish Pirate! Please remember to /close this post once your question has been answered!

dan1st•3y ago

create both objects, set/initialize them appropriately and persist them

danishpirateOP•3y ago

Wouldn't it be a problem if I am adding an a BicycleRiderto an existing BicycleTeam? I have to create the object by pulling it from the database and since BicycleTeamcontains of a list of all riders it could take a long time to create the object if there are a ton of BicycleRiderobjects who have a relations to it. I have used that approach, but just curious if there is a better way.

 @Override
    public void saveRider(BicycleRider bicycleRider, Long bicycleTeamID) {
        BicycleTeam bicycleTeam = bicycleTeamRepository.getReferenceById(bicycleTeamID);
        System.out.println(bicycleTeam.getBicycleRiderList());
        bicycleRider.setBicycleTeam(bicycleTeam);
        bicycleRiderRepository.save(bicycleRider);
    }

 @Override
    public void saveRider(BicycleRider bicycleRider, Long bicycleTeamID) {
        BicycleTeam bicycleTeam = bicycleTeamRepository.getReferenceById(bicycleTeamID);
        System.out.println(bicycleTeam.getBicycleRiderList());
        bicycleRider.setBicycleTeam(bicycleTeam);
        bicycleRiderRepository.save(bicycleRider);
    }

dan1st•3y ago

should be fine reusing existing (persisted) objects is perfectly fine

danishpirateOP•3y ago

Would it work if I were to create a new BicycleTeamobject using data from an existing one, but excluding the list of riders from it?

dan1st•3y ago

why don't you just use the existing object?

danishpirateOP•3y ago

I'm just worried about loading about retrieving a large objects from the database. This approach doesn't seem very scale-able

dan1st•3y ago

Do you use lazy fetching?

danishpirateOP•3y ago

Yes

dan1st•3y ago

if you add a bicycle to the (lazily loaded) list, does it work without loading it?

danishpirateOP•3y ago

You mean like this:

 public void saveRider(BicycleRider bicycleRider, Long bicycleTeamID) {
        BicycleTeam bicycleTeam = bicycleTeamRepository.getReferenceById(bicycleTeamID);
        bicycleTeam.getBicycleRiderList().add(new BicycleRider());
        bicycleRider.setBicycleTeam(bicycleTeam);
        bicycleRiderRepository.save(bicycleRider);
    }

 public void saveRider(BicycleRider bicycleRider, Long bicycleTeamID) {
        BicycleTeam bicycleTeam = bicycleTeamRepository.getReferenceById(bicycleTeamID);
        bicycleTeam.getBicycleRiderList().add(new BicycleRider());
        bicycleRider.setBicycleTeam(bicycleTeam);
        bicycleRiderRepository.save(bicycleRider);
    }

Should I be adding the rider to the riderteam and saving it or adding the riderteam to the rider and saving or does it not matter?

dan1st•3y ago

try adding to it at the beginning and check whether it works and check that it doesn't load all the objects

danishpirateOP•3y ago

Is there a way to override lazy loading?

 @Override
    public List<BicycleRider> findAll() {
        return bicycleRiderRepository.findAll();
    }

 @Override
    public List<BicycleRider> findAll() {
        return bicycleRiderRepository.findAll();
    }

I want to return a list of all BicycleRiderobjects, but due to lazy loading I get an error. I can fix it by choosing eager loading for BicycleRider, but I am not sure if I want to do that.

Unknown User•3y ago

Message Not Public

danishpirateOP•3y ago

What should I do instead? I can't return a list of all BicycleRiderfrom the endpoint without getting

Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.http.converter.HttpMessageConversionException: Type definition error: [simple type, class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.ArrayList[0]->pirate.tourdefrance24timersopgave.model.BicycleRider["bicycleTeam"]->pirate.tourdefrance24timersopgave.model.BicycleTeam$HibernateProxy$1DntwsM8["hibernateLazyInitializer"])] with root cause

Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.http.converter.HttpMessageConversionException: Type definition error: [simple type, class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.ArrayList[0]->pirate.tourdefrance24timersopgave.model.BicycleRider["bicycleTeam"]->pirate.tourdefrance24timersopgave.model.BicycleTeam$HibernateProxy$1DntwsM8["hibernateLazyInitializer"])] with root cause

dan1st•3y ago

You typically want eager loading when you (almost) always need the collection when needing the object e.g. if you have a role-->permission mapping, you might want to load the permissions eagerly when loading the roles and the fetch = FetchType.LAZY specifies whether to load it lazily or eagerly Can you show the whole stack trace?

danishpirateOP•3y ago

Sure, just a sec

dan1st•3y ago

btw Spring allows you to log all the executed SQL statements for testing

danishpirateOP•3y ago

https://pastebin.com/1rF6hqgF

Pastebin

Hibernate: select bicyclerid0_.id as id10, bicyclerid0_.bicyclete...

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