将null传递给JPA OneToOne persisted

Question

@Entity
@Table(name="EMPLOYEES")
public class Employee {

@Id
public Integer EMPLOYEE_ID;

public String FIRST_NAME;

public String LAST_NAME;

@OneToOne
@JoinColumn(name= "JOB_ID")
public Job Job;

@OneToOne
@JoinColumn(name="MANAGER_ID")
public Employee Manager;

@OneToOne
@JoinColumn(name= "DEPARTMENT_ID")
public Department Department;

}

@Entity
@Table(name="JOBS")
public class Job {

@Id
public String JOB_ID;

public String JOB_TITLE;

}

@Entity
@Table(name="DEPARTMENTS")
public class Department {

@Id
public Integer DEPARTMENT_ID;

public String DEPARTMENT_NAME;

@OneToOne(cascade = {CascadeType.ALL})
@JoinColumn(name="MANAGER_ID")
public Employee Manager;
}

public void save () {
int intSize = listSize + 1;
for (int i= 0; i < intSize; i++) {
Employee employee = new Employee();

Job job = new Job();
job.JOB_ID = employees.get("empJobId" + i);

Department dept = new Department();
dept.DEPARTMENT_ID = ParseUtil.stringToInt(employees.get("empDeptId" + i));

Employee manager = new Employee();
manager.EMPLOYEE_ID = ParseUtil.stringToInt(employees.get("empMgrId" + i));

Integer intId =  ParseUtil.stringToInt(employees.get("empId" + i));
employee.EMPLOYEE_ID = intId;
employee.FIRST_NAME = employees.get("empFirstName" + i);
employee.LAST_NAME = employees.get("empLastName" + i);
employee.Job = job;
employee.Department = dept;
employee.Manager = manager;
EmpDomain.updateEmp(employee);
}
}

和empdomain.updateemp（）

public static void updateEmp(Employee employee) {
  JPA.em().merge(employee);
}

我只是一个新手玩2，jpa持久化，所以我不知道如何修复异常错误，请帮助。

Answer 1

您似乎试图将这些依赖关系映射为双向的。

在这种情况下，您必须告诉持久化提供者哪个是关系的所有方/所有方。

例如，如果Employee是所属方，则应将映射更改为：

@OneToOne(mappedBy = "Manager", cascade = {CascadeType.PERSIST, CascadeType.MERGE})
public Department Department;