如何刪除“空ID…條目（在發生異常后不要刷新會話）”

Question

您好，我是php的Web開發人員，最近遷移到javaEE。我在mysql中創建了表。 這是頭等艙：

@Entity
@Table(name = "first")
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)   
@org.hibernate.annotations.Cache(usage = CacheConcurrencyStrategy.READ_WRITE,     inclu`enter code here`de = "all")
public class first extends second {

@OneToOne(cascade = CascadeType.ALL)
private second A;

。 。 。 這是我的第二堂課：

    @Entity
    @Table(name = "second", uniqueConstraints =
    @UniqueConstraint(columnNames = {"feildone", "feildtwo"}))
    public class second implements Serializable {
    @OneToOne(cascade = CascadeType.ALL, mappedBy = "first")
    public static final String FindOne = "findOne";
    @Id
    @GeneratedValue
    Integer id;
    private String feildtwo;
    private String feildone;
    @Temporal(javax.persistence.TemporalType.DATE)
    private Date createTime;
    @OneToMany(cascade = CascadeType.ALL)
    public List<Progress> progress = new ArrayList<>();
    private Integer num;

。 。 。

Answer 1

嘗試自動生成您的ID，看看您是否遇到相同的問題

 @Entity
        @Table(name = "second", uniqueConstraints =
        @UniqueConstraint(columnNames = {"feildone", "feildtwo"}))
        public class second implements Serializable {
        @OneToOne(cascade = CascadeType.ALL, mappedBy = "first")
        public static final String FindOne = "findOne";
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO) // try to use auto generate id guess this might help
        Integer id;
        private String feildtwo;
        private String feildone;
        @Temporal(javax.persistence.TemporalType.DATE)
        private Date createTime;
        @OneToMany(cascade = CascadeType.ALL)
        public List<Progress> progress = new ArrayList<>();
        private Integer num;