我有一个复合键ContractServiceLocationPK，它由可嵌入类中的long类型的三个id(contractId，locationId和serviceId)组成。使用此复合键的类ContractServiceLocation，使用@MapsId批注将这些id映射到它们的对象。外观如下(已删除的setter/getter和不相关的属性):
契约(Contract)
@Entity
@Table(name = "Contract")
public class Contract implements Serializable {
public Contract() {
}
@Id
@GeneratedValue
private long id;
@OneToMany(mappedBy = "contract", cascade = CascadeType.ALL, fetch= FetchType.EAGER)
Collection<ContractServiceLocation> contractServiceLocation;
}
ContractServiceLocationPK
@Embeddable
public class ContractServiceLocationPK implements Serializable {
private long contractId;
private long locationId;
private long serviceId;
}
ContractServiceLocation
@Entity
@Table(name="Contract_Service_Location")
public class ContractServiceLocation implements Serializable {
@EmbeddedId
ContractServiceLocationPK id;
@ManyToOne(cascade = CascadeType.ALL)
@MapsId("contractId")
Contract contract;
@ManyToOne(cascade = CascadeType.ALL)
@MapsId("locationId")
Location location;
@ManyToOne(cascade = CascadeType.ALL)
@MapsId("serviceId")
Service service;
BigDecimal price;
}
尝试以任何方式(直接或通过契约(Contract))持久化ContractServiceLocation类型的对象时，我得到:
Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.PropertyAccessException: could not set a field value by reflection setter of com.test.model.ContractServiceLocationPK.contractId
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1763)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1677)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1683)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:1187)
at com.test.MainTest.main(MainTest.java:139)
Caused by: org.hibernate.PropertyAccessException: could not set a field value by reflection setter of com.test.model.ContractServiceLocationPK.contractId
at org.hibernate.property.DirectPropertyAccessor$DirectSetter.set(DirectPropertyAccessor.java:134)
at org.hibernate.mapping.Component$ValueGenerationPlan.execute(Component.java:441)
at org.hibernate.id.CompositeNestedGeneratedValueGenerator.generate(CompositeNestedGeneratedValueGenerator.java:121)
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:117)
at org.hibernate.jpa.event.internal.core.JpaPersistEventListener.saveWithGeneratedId(JpaPersistEventListener.java:84)
at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:206)
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:149)
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:75)
at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:811)
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:784)
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:1181)
... 1 more
Caused by: java.lang.NullPointerException
at sun.reflect.UnsafeFieldAccessorImpl.ensureObj(Unknown Source)
at sun.reflect.UnsafeLongFieldAccessorImpl.set(Unknown Source)
at java.lang.reflect.Field.set(Unknown Source)
at org.hibernate.property.DirectPropertyAccessor$DirectSetter.set(DirectPropertyAccessor.java:122)
... 12 more
我的假设是，JPA/Hibernate期望使用Contract对象而不是long变量，但是如果我将embeddable中的变量从long更改为它们的类型，则会得到
The type of the ID mapped by the relationship 'contract' does not agree with the primary key class of the target entity.。如果我尝试使用id类而不是可嵌入的，则在Contract的OneToMany映射中使用mappedby，我会得到In attribute 'contractServiceLocation', the "mapped by" attribute 'contract' has an invalid mapping type for this relationship.。如何制作具有多个ManyToOne映射的组合键？编辑:添加了一个片段，在其中我尝试保留项目:
Service service = new Service();
// Set all service properties
Contract contract = new Contract();
// Set all contract properties
Location location = new Location();
// Set all location properties
ContractServiceLocation csl = new ContractServiceLocation();
csl.setContract(contract);
csl.setLocation(location);
csl.setService(service);
Collection<ContractServiceLocation> cslItems = new ArrayList<>();
cslItems.add(csl);
em.getTransaction().begin();
em.persist(location);
em.persist(service);
em.persist(csl);
em.persist(contract);
em.getTransaction().commit();
之所以看起来像这样而不是包含在某些DAO中，是因为在继续开发应用程序的其余部分之前，我先生成数据库并测试项目。
编辑2:我已经重写了我的模型，现在一切似乎都可以正常工作，除了在Eclipse中，我遇到了持续的错误。当前情况如下:
契约(Contract)-不变(除去急切的装载物)
ContractServiceLocationPK-现在是一个ID类
public class ContractServiceLocationPK implements Serializable {
@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinColumn(name = "contract_id")
private Contract contract;
@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinColumn(name = "location_id")
private Location location;
@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinColumn(name = "service_id")
private Service service;
//getters and setters
//overridden equals() and hashCode()
}
ContractServiceLocation
@Entity
@Table(name="Contract_Service_Location")
@IdClass(ContractServiceLocationPK.class)
public class ContractServiceLocation implements Serializable {
@Id
Contract contract;
@Id
Location location;
@Id
Service service;
BigDecimal price;
//getters and setters
//overridden equals() and hashCode()
}
目前，这似乎可以正常工作。它创建一个复合键，并与所有复合属性保持多对一关系。但是有些奇怪。在Contract中，eclipse在
mappedBy批注的@OneToMany批注上标记ContractServiceLocation，并显示错误消息In attribute 'contractServiceLocation', the "mapped by" attribute 'contract' has an invalid mapping type for this relationship.。我假设这是因为Contract中定义的ContractServiceLocation属性没有@ManyToOne批注，但是在复合类中定义了该批注。我是否偶然发现了“不合规的JPA但与Hibernate一起工作”陷阱，或者这是怎么回事？ 最佳答案
对于您的原始问题(未修改的变体):
您必须在ContractServiceLocation类中实例化“ContractServiceLocationPK id”。替换行:
有了这个:
然后它应该工作。因为Hibernate试图在内部设置属性，但是在NullPointerException上失败。
关于java - 具有ManyToOne的JPA复合键，获得org.hibernate.PropertyAccessException : could not set a field value by reflection setter of，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/23736422/