重复输入例外：Spring Hibernate / JPA级联保存多对一

时间：2019-02-18 13:31:58

标签： java spring hibernate jpa

这是一个Spring应用程序（没有Spring Boot）。 我正在使用的数据库是MySQL。 我遇到的问题是保存实体Driver时，该实体在Carrier和Location上都具有多对一关系。

当我在Driver上进行保存时，我想做的是。驱动程序以及位置和运营商将持久保存到数据库中。我遇到的问题是尝试保存时。我收到重复的密钥冲突

堆栈跟踪： 

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

实体/模型类：（已删除获取器/设置器） 

@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>();


}

编写实体的代码 

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;
    }

问题：是否有可能实现我想做的事情？如果我尝试保存location和driver并将其与@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; } 关联，则希望休眠处理这些关系，如果它已经保存而不是尝试再次保存。 如果没有，建议的保存这些实体的方法是什么？

数据源配置 

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

}

更新＃2

具有这样的DriverRepository 

repository.saveAll(drivers);

要保存： 

quad

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

我添加了github链接，以防有人愿意尝试。

6 个答案:

答案 0 :(得分：4)

我准备了有效解决方案：Cepr0/greyhound-demo。 我稍微修改了您的项目-使用Spring-Boot，Lombok和H2数据库完成了该项目，仅出于演示目的并简化它。

因此，如果我没记错的话，任务是转换“ 任务”（从灵缇犬网站开始）：

{
    "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"
        }
    ]
}

三个实体： Driver ， Location 和 Carrier ，它们之间的关系： 

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

即Driver与Location和Carrier具有“多对一”关系。

此任务的主要问题是，在保存Driver实体时，我们需要使用已经持久保存的 Location和Carrier实体，或者使用新的。因此，要解决它，我们必须：

  1. 为这些实体准备3个存储库。
  2. 对于每个与“ Location”和“ Carrier”相关的“任务” 查找。
  3. 如果找不到Location和Carrier，则创建新的。
  4. 创建新的Driver并设置找到的Location和Carrier或已创建的新对象。
  5. 坚持使用Driver（如果找不到，则级联保持Location和Carrier）。

方法GreyhoundService.process()的最终代码：

@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);
      });
}

为了最小化数据库中数据的大小和SQL选择的数量，我对初始实体进行了如下转换：

驱动程序 

@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;
    }
}

位置 

@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;
    }
}

运营商 

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

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

如您所见，我使用了Location和Carrier的自然标识符（以及Carrier中的复合标识符）。这样不仅可以减少数据的大小，而且可以减少Hibernate在存储复杂实体时执行的其他SQL查询的数量。填充Location和Carrier表后，Hibernate不会执行不必​​要的查询来查找它们，而是从其自己的缓存中获取数据（您可以在应用程序日志中看到它）。

P.S。请注意，此解决方案不是最佳的。 IMO为了使它更好，您可以将主要过程分为两部分：第一个过程持久保存不同的Location和Carrier，而第二个过程持久保存Driver s而没有找到{{1 }}和Location。这两个部分都与batch insert一起执行。

更新

以最佳解决方案分支：Cepr0/greyhound-demo:async_and_batch_insert

由于位置和运营商的异步保留以及批量插入，处理仅需约5秒钟。

答案 1 :(得分：1)

由于Location和Carrier已经过版本控制，并且您没有在创建的实例中设置版本，因此Hibernate可能只会认为它们是新的并尝试插入它们（否则，如果需要它们要进行更新，Hibernate始终不知道要比较哪个版本，因为更新的实例中缺少该版本。

首先，您需要：

  • 从数据库中获取现有的Location和Carrier实例，如果它们不是新的，则对其进行更新（通过检查是否设置了id即可知道）；
  • 或正确传播和设置版本属性以及ID和业务属性。

第二，在当前的实体映射中，您还有两种选择（以及让Hibernate正确保存整个图形的既定目标）：

  • 如果您不使用交易，则对于以上两种情况，您都必须求助于entityManager.merge(driver)，以便正确插入或更新所有内容；
  • 否则，只有当您选择上面的第一个选项并读取现有的Location和Carrier实例并在同一事务中调用repository.saveAll(drivers)时，它才会起作用，因为驱动程序实例将是持久化，PERSIST操作将级联到仍附加的位置和载体实例。

根据您项目中使用的体系结构选择和约定，还有（许多）其他可能性，即，我永远不会从many到one这边层叠ALL（一个不希望的结果是删除） ，而且在大多数情况下，我总是会分别明确地保存one面，但这取决于您。

答案 2 :(得分：0)

您还需要在Carrier和Location中使用已包装的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);
    }

由于您使用了双向映射（@OneToMany），因此需要完成此操作

更新：

使用JPA级联配置，而不是休眠一个：

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

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

更新2

仔细查看您的项目后，您似乎缺少以下事务设置：

@Transactional
public void process() {

在该方法内，您将执行许多存储库操作，这很好，因为所有SimpleJpaRepository方法都是事务性的。

我认为问题在于，并非所有这些操作都在同一事务下并有效地实现了持久化。 （每个操作都在自己的小事务内运行，然后所有实体都与持久性上下文分离）。

注意：您可能需要进行一些配置才能启用@Transactional注释设置。

答案 3 :(得分：0)

解决此问题的一种方法是仅加载所有位置和载体，因此使用findById（）将它们绑定到您的会话。使用这些获得的对象在新的驱动程序对象上进行设置。这应该可以解决问题。

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);
}

看起来像这样。这只是一个简单的示例，因为我不知道实际的上下文。

答案 4 :(得分：0)

当它要在双方插入条目时导致重复的问题。 解决方案是将一侧标记为另一侧“映射”。

因此可在Carrier类中使用：

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

在Location类中：

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

答案 5 :(得分：0)

我们需要将标识符作为引用的列名进行传递。如下所示映射位置实体。

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