如何删除“空ID…条目（在发生异常后不要刷新会话）”

Question

hello،I am web developer in php and recently migrateto javaEE.I create to table in mysql. this is first class:

@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;

. . . and this is my second class:

    @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

Try generating your ID automatically and see if u face the same problem

 @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;