java - TransientObjectException 即使我设置了cascade=CascadeType.ALL

Question

我有两个类:

Employee.java

@Entity
@Table
public class Employee {
    @Id
    @GeneratedValue
    private Long id;

    private String name;

    @ManyToOne
    private Department department;

    public Employee() {}

    public Employee(String name, Department department) {
        this.name = name;
        this.department = department;
    }


    public Employee(String name) {
        this.name = name;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    @Override
    public String toString() {
        return "Employee [id=" + id + ", name=" + name + ", department="
                + department.getName() + "]";
    }

}

部门.java

@Entity
@Table
public class Department {

    @Id
    @GeneratedValue
    private Long id;


    private String name;

    @OneToMany(mappedBy="department",cascade=CascadeType.ALL)
    private List<Employee> employees = new ArrayList<Employee>();

    public Department() {
        super();
    }
    public Department(String name) {
        this.name = name;
    }
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public List<Employee> getEmployees() {
        return employees;
    }
    public void setEmployees(List<Employee> employees) {
        this.employees = employees;
    }
}

然后我尝试在主方法中保存部门和员工:

Session session = HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();

Department department = new Department("java");
//session.save(department); //throw org.hibernate.TransientObjectException if I comment the line

session.save(new Employee("Jakab Gipsz",department));
session.save(new Employee("Captain Nemo",department));

session.getTransaction().commit();

没成功。它抛出了一个错误:

org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.learn.hibernate.Department

但是如果我取消注释行 session.save(department);，一切都会正常工作。为什么？我已经设置了 cascade=CascadeType.ALL，因此它应该自动保存 department 而不会引发任何错误。我错过了什么吗？

Answer 1

当您保存员工时，不会保存部门，因为没有级联。如果你想要这样，你需要在 Employee 类中添加一个级联。

@ManyToOne(cascade = CascadeType.save)
private Department department;