休眠一对一关系和外键问题

Question

我有一个奇怪的问题，我无法找到。我有两个类，员工和地址，用于创建两个具有一对一关系的表。 当我检查操作的结果时，我看到记录已添加，但没有外键到表中的地址 员工示例：

1   John      Smith     12333    null

其中 null address_ID。 当我检查地址表时，我看到添加了记录，但id的起始数是两个。

2   New York    st. Aperman 234 12  03999

员工.class

@Entity
public class Employee {
@Id
@GeneratedValue
private long id;
private String firstName;
private String lastName;
private double salary;
@OneToOne 
@JoinColumn(name = "address_ID") 
private Address address;
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}

}

地址.class

@Entity
public class Address {
@Id
@GeneratedValue
private long id;
public String locality;
public String zipCode;
public String street;
public int streetNumber;

public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getLocality() {
return locality;
}
public void setLocality(String locality) {
this.locality = locality;
}
public String getZipCode() {
return zipCode;
}
public void setZipCode(String zipCode) {
this.zipCode = zipCode;
}
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
public int getStreetNumber() {
return streetNumber;
}
public void setStreetNumber(int streetNumber) {
this.streetNumber = streetNumber;
}

}

主.class

public class Main {
public static void main(String[] args) {
EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("tutorialdb");
EntityManager entityManager = entityManagerFactory.createEntityManager();
Employee employee = new Employee();
Address adres = new Address();      
employee.setFirstName("John");
employee.setLastName("Smith");
employee.setSalary(12333.0);
adres.setLocality("New York");
adres.setZipCode("03999");
adres.setStreet("st. Aperman 234");
adres.setStreetNumber(12);
entityManager.getTransaction().begin();
entityManager.persist(employee);
entityManager.persist(adres);
entityManager.getTransaction().commit();

entityManager.close();
entityManagerFactory.close();
}

}

坚持不懈.xml

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<persistence-unit name="tutorialdb"
transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<properties>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="javax.persistence.jdbc.user" value="user"/>
<property name="javax.persistence.jdbc.password" value="password"/>
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/tutorial"/>
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL8Dialect"/>
<property name="hibernate.hbm2ddl.auto" value="create"/>
</properties>
</persistence-unit>

Answer 1

在保留之前，您需要在Employee中设置Address引用。

Address adres = new Address();
...
employee.setAddress(adres);

雇员表中的外键null，因为Employee中未设置地址。