Spring 和 Hibernate 错误——非空属性引用空值或瞬态值：com.tharaka.model.Employee.designation

Question

我是 Spring 和 hibernate 的新手，尝试持久化事务数据时出现上述错误。请尝试解决这个问题 这是我的实体：

 @Entity @NamedQuery(name="Employee.findAll", query="SELECT e FROM    Employee e") 

    public class Employee implements Serializable{      

    private    static final long serialVersionUID = 1L;     
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)   
    private int id;
    private String city;    
    private String civil;
    @Temporal(TemporalType.DATE)    
    @Column(name="dob", length=11)
    private Date dob;   
    private String email;   
    private int epf;    
    private String fname;   
    private String gender;  
    private int landtp;     
    private String lname;   
    @Temporal(TemporalType.DATE)
    @Column(name="salaryincrement", length=11)  
   //bi-directional many-to-one association to    Designation   
   @ManyToOne(fetch = FetchType.LAZY)
   @JoinColumn(name="designation_id", nullable=false)   
   private    Designation designation;  

   public Employee() {  }



    @Entity
    @NamedQuery(name="Designation.findAll", query="SELECT d FROM Designation d")
    public class Designation implements Serializable{ 
      private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private int id;

    private String type;

    //bi-directional many-to-one association to Employee
    @OneToMany(mappedBy="designation")//, cascade=CascadeType.ALL
    private List<Employee> employees;

    public Designation() {
            }

这是我的实体类， 实体有一个 getter 和一个 setter

Answer 1

designation 设置为 nullable = false。但是employees 变量未在Designation 中初始化。所以，你必须初始化为

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

Answer 2

我不确定您是否可以使用原始类型 int 作为您的 ID - 您可能应该使用 Integer - 因为 int 具有默认零值并且不能为 null，您的新记录可以被视为 ID 为零的独立实体，而不是临时实体。

同样的错误出现在Designation 类中。

见Primitive or wrapper for hibernate primary keys