Duplicate Entry Exception: Spring Hibernate/JPA cascade save Many To One

Question

It is a spring application (no spring boot). The database I am using is MySQL. The issue I am having is when saving the entity Driver which has a Many to one relationship on both Carrier and Location.

What I want to do is, when I do the save on Driver. Driver along with Location and Carrier is persisted to the database. The issue I am having is when trying to save. I get duplicate key violation

Stack trace:

org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 1062, SQLState: 23000
Feb 18, 2019 1:25:42 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: Duplicate entry '910327' for key 'UK_lheij6i9eldhfhyu9j1q5fjls'
Exception in thread "main" org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [UK_lheij6i9eldhfhyu9j1q5fjls]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement
    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:296)
    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:253)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:527)
    at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:61)
    at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:242)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:153)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:135)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:93)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
    at com.sun.proxy.$Proxy47.saveAll(Unknown Source)
    at greyhound.service.GreyhoundServiceImpl.process(GreyhoundServiceImpl.java:38)
    at greyhound.Main.main(Main.java:17)
Caused by: org.hibernate.exception.ConstraintViolationException: could not execute statement
    at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:59)
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:113)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:99)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:178)
    at org.hibernate.dialect.identity.GetGeneratedKeysDelegate.executeAndExtract(GetGeneratedKeysDelegate.java:57)
    at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:42)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3073)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3666)
    at org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:81)
    at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:645)
    at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:282)
    at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:263)
    at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:317)
    at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:332)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:289)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:196)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:127)
    at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:192)
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:135)
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:828)
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:795)
    at org.hibernate.engine.spi.CascadingActions$7.cascade(CascadingActions.java:298)
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:490)
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:415)
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:216)
    at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:149)
    at org.hibernate.event.internal.AbstractSaveEventListener.cascadeBeforeSave(AbstractSaveEventListener.java:428)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:266)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:196)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:127)
    at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:192)
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:135)
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:62)
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:804)
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:308)
    at com.sun.proxy.$Proxy44.persist(Unknown Source)
    at org.springframework.data.jpa.repository.support.SimpleJpaRepository.save(SimpleJpaRepository.java:489)
    at org.springframework.data.jpa.repository.support.SimpleJpaRepository.saveAll(SimpleJpaRepository.java:521)
    at org.springframework.data.jpa.repository.support.SimpleJpaRepository.saveAll(SimpleJpaRepository.java:73)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:359)
    at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:200)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:644)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:608)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.lambda$invoke$3(RepositoryFactorySupport.java:595)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:595)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:59)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:294)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139)
    ... 11 more
Caused by: java.sql.SQLIntegrityConstraintViolationException: Duplicate entry '910327' for key 'UK_lheij6i9eldhfhyu9j1q5fjls'
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:117)
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:970)
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1109)
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1057)
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeLargeUpdate(ClientPreparedStatement.java:1377)
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdate(ClientPreparedStatement.java:1042)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:175)
    ... 69 more

Process finished with exit code 1

Entity/Model classes: (Have removed getters/setters)

@Entity
@Table(name = "Driver")
public class Driver {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Version
    @Column(name = "version")
    private int version;
    @Column(name = "driver_id")
    private Long driverId;
    @Column(name = "first_name")
    private String firstName;
    @Column(name = "last_name")
    private String lastName;
    @Column(name = "middle_init")
    private String middleInitial;

    @ManyToOne(fetch = FetchType.EAGER)
    @Cascade({CascadeType.ALL})
    private Carrier carrier;

    @ManyToOne(fetch = FetchType.EAGER)
    @Cascade({CascadeType.ALL})
    private Location location;


@Entity
@Table(name="Carrier")
public class Carrier {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Version
    @Column(name = "version")
    private int version;

    @PrimaryKeyJoinColumn
    @Column(name = "carrier_name")
    private String carrierName;

    @OneToMany
    @JoinColumn(name = "carrier_id", referencedColumnName = "id")



@Entity
@Table(name="Locations")
public class Location {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Long id;

    @Version
    private Long version;
    @Column(name = "location_id")
    private Long locationId;
    @Column(name = "location_name")
    private String locationName;

    @OneToMany
    @JoinColumn(name = "location_id", referencedColumnName = "location_id")
    private List<Driver> drivers = new ArrayList<Driver>();


}

Code preparing the entities

private List<Driver> prepareEntityList(Result result) {
        List<Driver> drivers = new ArrayList<Driver>();

        for(DriverAssignment driverAssignment : result.getDriverAssignments()) {
            Location location = new Location();
            location.setLocationName(driverAssignment.getHomeLocation3());
            location.setLocationId(driverAssignment.getHomeLocation());
            Carrier carrier = new Carrier();
            carrier.setCarrierName(driverAssignment.getCarrierId());
            Driver driver = new Driver();
            driver.setDriverId(driverAssignment.getDriverId());
            driver.setFirstName(driverAssignment.getFirstName());
            driver.setLastName(driverAssignment.getLastName());
            driver.setMiddleInitial(driverAssignment.getMiddleInitial());
            driver.setCarrier(carrier);
            driver.setLocation(location);
            drivers.add(driver);
        }

        return drivers;
    }

Question: is it possible to achieve what I am trying to do? Expect hibernate to handle the relationships when I try to save and associate a location with a driver if it has already been saved instead of trying to save it again. If not, what is a suggested approach to save these entities?

Datasource configuration

@Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(dataSource());
        em.setPackagesToScan(new String[] { "greyhound" });

        JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        em.setJpaVendorAdapter(vendorAdapter);
        em.setJpaProperties(additionalProperties());

        return em;
    }

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName("com.mysql.cj.jdbc.Driver");
        dataSource.setUrl("jdbc:mysql://localhost:3306/greyhound1");
        dataSource.setUsername("root");
        dataSource.setPassword("");
        return dataSource;
    }

    @Bean
    public PlatformTransactionManager transactionManager(EntityManagerFactory emf) {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(emf);

        return transactionManager;
    }

    @Bean
    public PersistenceExceptionTranslationPostProcessor exceptionTranslation() {
        return new PersistenceExceptionTranslationPostProcessor();
    }

    Properties additionalProperties() {
        Properties properties = new Properties();
        properties.setProperty("hibernate.hbm2ddl.auto", "create-drop");
        properties.setProperty("hibernate.dialect", "org.hibernate.dialect.MySQL5Dialect");

        return properties;
    }

Update #2

Have a DriverRepository like this

@Repository
public interface DriverRepository extends JpaRepository<Driver, Long> {

}

To save:

repository.saveAll(drivers);

Github link https://github.com/mukulgoel1989/greyhound

I have added the github link in case someone is willing to give this a try.

Answer 1

I prepared the working solution: Cepr0/greyhound-demo. I reworked your project "a little" - did it with Spring-Boot, Lombok and H2 database, just for demo purposes and to simplify it.

So, if I'm not mistaken, the task is to transform 'assignments' (from the greyhound site):

{
    "results": [
        {
            "oper_nbr": 1,
            "carrier_cd": "GLX ",
            "last_name": "JOHN",
            "first_name": "SMITH",
            "middle_init": null,
            "home_loc_6": 12345,
            "home_loc_3": "NLX",
            "oper_class": "T"
        },
        {
            "oper_nbr": 2,
            "carrier_cd": "GLX ",
            "last_name": "JOHN",
            "first_name": "DOE",
            "middle_init": null,
            "home_loc_6": 67890,
            "home_loc_3": "NLX",
            "oper_class": "T"
        }
    ]
}

to three entities: Driver, Location, and Carrier with the relations:

Location -1---*- Driver -*---1- Carrier

i.e. Driver has 'many-to-one' relation with Location and Carrier.

The main problem of this task is that while saving the Driver entity, we need to use the already persisted Location and Carrier entities, or use new ones. So to solve it we have to:

1. Prepare 3 repositories for those entities.
2. For each 'assignment' find related Location and Carrier.
3. If Location and Carrier are not found then create new ones.
4. Create a new Driver and set the found Location and Carrier or new ones having been created.
5. Persist the Driver (and cascaded persist Location and Carrier if they are not found).

The final code of method GreyhoundService.process():

@Transactional
public void process() {
  client.getAssignments()
      .stream()
      .forEach(a -> {
        log.debug("[d] Assignment: {}", a);

        Driver driver = new Driver();

        driver.setId(a.getDriverId());
        driver.setFirstName(a.getFirstName());
        driver.setLastName(a.getLastName());
        driver.setMiddleName(a.getMiddleName());

        driver.setLocation(
            locationRepo.findById(new Location.PK(a.getLocationId(), a.getLocationName()))
                .orElse(new Location(a.getLocationId(), a.getLocationName()))
        );

        driver.setCarrier(
            carrierRepo.findById(a.getCarrierId().trim())
                .orElse(new Carrier(a.getCarrierId().trim()))
        );

        driverRepo.saveAndFlush(driver);

        log.debug("[d] Driver: {}", driver);
      });
}

To minimize the size of the data in the database and the number of SQL selects I transformed the initial entities as follows:

Driver

@Getter
@Setter
@ToString
@EqualsAndHashCode(of = "id")
@Entity
@Table(name = "drivers")
public class Driver implements Persistable<Long> {

    @Id private Long id;

    private String firstName;
    private String lastName;
    private String middleName;

    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumn(name = "carrierId", foreignKey = @ForeignKey(name = "drivers_carriers"))
    private Carrier carrier;

    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumns(
            value = {@JoinColumn(name = "locationId"), @JoinColumn(name = "locationName")},
            foreignKey = @ForeignKey(name = "drivers_locations")
    )
    private Location location;

    @Override
    public boolean isNew() {
        return true;
    }
}

Location

@Data
@NoArgsConstructor
@Entity
@Table(name = "locations")
@IdClass(Location.PK.class )
public class Location {

    @Id private Long locationId;
    @Id private String locationName;

    public PK getId() {
        return new PK(locationId, locationName);
    }

    public void setId(PK id) {
        this.locationId = id.getLocationId();
        this.locationName = id.getLocationName();
    }

    public Location(final Long locationId, final String locationName) {
        this.locationId = locationId;
        this.locationName = locationName;
    }

    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public static class PK implements Serializable {
        private Long locationId;
        private String locationName;
    }
}

Carrier

@Data
@NoArgsConstructor
@Entity
@Table(name = "carriers")
public class Carrier {
    @Id private String carrierId;

    public Carrier(final String carrierId) {
        this.carrierId = carrierId;
    }
}

As you can see I used natural identifiers for Location and Carrier (and a composite one in Carrier). This made it possible not only to reduce the size of the data but also reduce the number of additional SQL queries that Hibernate performs when storing complex entities. When Location and Carrier tables are filled, Hibernate does not perform unnecessary queries to find them but takes their data from its own cache (you can see this in the app log).

P.S. Note that this solution is not optimal. IMO to make it better you can split the main process into two parts: the first one persists distinct Locations and Carriers and the second one just persists Drivers without finding Locations and Carriers. Both parts perform with batch insert.

UPDATE

Branch with the optimal solution: Cepr0/greyhound-demo:async_and_batch_insert

Due to the asynchronous persisting of Locations and Carriers and with batch insert, processing takes only about 5 seconds.

Answer 2

Since Location and Carrier are versioned and you don't set the version in the instances you create, Hibernate probably just considers them new and tries to insert them (otherwise, if they'd need to be updated, Hibernate would anyway not know which versions to compare since it's missing in the updated instances).

Firstly, you need either to:

• fetch existing Location and Carrier instances from db and update them if they're not new (you know that by checking if id is set);
• or properly propagate and set version attribute as well together with id and business attributes.

Secondly, you also have two choices with your current entity mappings (and the stated goal to let Hibernate save the entire graph properly):

• if you don't use transactions, then for both of the above you have to resort to entityManager.merge(driver) so that everything is properly either inserted or updated;
• otherwise and only if you pick the first option above and read existing Location and Carrier instances and call repository.saveAll(drivers) in the same transaction, then it would work, because driver instances would be persisted and PERSIST operation would be cascaded to still attached location and carrier instances.

There are (many) other possibilities depending on the architectural choices and conventions used in you project, i.e. I would never cascade ALL from many side to one side (an example undesired consequence is removal), and I would in most cases always explicitly save the one side separately, but it's up to you.

Answer 3

We need to pass the identifier as a referenced column name. Map the Location entity like below.

@OneToMany
@JoinColumn(name = "location_id", referencedColumnName = "id")
private List<Driver> drivers = new ArrayList<Driver>();

Answer 4

duplicate problem is causing when it goes to insert entries for both sides. The solution is to mark one side as 'mappedby' the other.

so use in Carrier Class:

@OneToMany(mappedBy="carrier")
@JoinColumn(name = "carrier_id", referencedColumnName = "id")
private List<Driver> drivers = new ArrayList<Driver>();

And in Location Class:

@OneToMany(mappedBy="location")
@JoinColumn(name = "location_id", referencedColumnName = "location_id")
private List<Driver> drivers = new ArrayList<Driver>();

Answer 5

You also need to populate Carrier and Location with the crated Driver:

  for(DriverAssignment driverAssignment : result.getDriverAssignments()) {
        Location location = new Location();
        Carrier carrier = new Carrier();
        Driver driver = new Driver();
        driver.setCarrier(carrier);
        driver.setLocation(location);

        // add this
        location.getDrivers().add(driver);
        carrier.getDrivers().add(driver);

        drivers.add(driver);
    }

this needs to be done due to the bi-directional mapping you used (@OneToMany)

Update:

Use JPA cascade config, not Hibernate one:

@ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private Carrier carrier;

@ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private Location location;

Update 2

After taking closer look at your project it seems that you are missing a transactional set-up on:

@Transactional
public void process() {

inside that method you are performing many repository operations which is fine as all SimpleJpaRepository methods are transactional.

The problem in my opinion is that not all of these operations are run under same transaction and effectively persistence context. (each operations runs within its own small transaction and after that all the entities are detached from the persistence context).

NOTE: you may need to play with configuration a bit to enable @Transactional annotation set-up.

Answer 6

One way to resolve this would be to just load all the locations and carriers so with a findById() this way they are bound to you session. Use these obtained objects to be set on you new driver objects. This should resolve the issue.

for(DriverAssignment driverAssignment : result.getDriverAssignments()) {
  Location location;
  if (driverAssignment.getHomeLocation() != null) {
    location = locationRepo.findById(driverAssignment.getHomeLocation());
  } else {
    location = new Location();
  }
  location.setLocationName(driverAssignment.getHomeLocation3());
  Carrier carrier;
  if (driverAssignment.getCarrierId() != null) {
    carrier = carrierRepo.findById(driverAssignment.getCarrierId());
  } else {
    carrier = new Carrier();
  }
  Driver driver;
  if (driverAssignment.getDriverId() != null) {
    driver = driverRepo.findById(driverAssignment.getCarrierId());
  } else {
    driver = new Driver();
  }
  driver.setDriverId(driverAssignment.getDriverId());
  driver.setFirstName(driverAssignment.getFirstName());
  driver.setLastName(driverAssignment.getLastName());
  driver.setMiddleInitial(driverAssignment.getMiddleInitial());
  driver.setCarrier(carrier);
  driver.setLocation(location);
  drivers.add(driver);
}

It would look something like this. This is just a simple example because I don't know the actual context.