的EclipseLink/JPA2多對一雙向級聯堅持問題

這類似於How to cascade persist using JPA/EclipseLink 的EclipseLink/JPA2多對一雙向級聯堅持問題

我有實體，像這樣。一個是RoomEntity，它與ComputerEntity具有一對多的雙向關係。例如。每個房間有0..n臺電腦。

@Entity 
public class ComputerEntity implements Serializable { 
    @Id 
    @GeneratedValue(generator="computerSeq",strategy= GenerationType.SEQUENCE) 
    @SequenceGenerator(name="computerSeq",sequenceName="SEQUENCECOMPUTERID",allocationSize=1) 
    private long computerID; 

    @Column(name = "COMPUTERID") 
    public long getComputerID() { 
     return computerID; 
    } 

    public void setComputerID(long computerID) { 
     this.computerID = computerID; 
    } 

    private RoomEntity room; 

    @ManyToOne() 
    @JoinColumn(name = "ROOMID", referencedColumnName = "ROOMID") 
    public RoomEntity getRoom() { 
     return room; 
    } 

    public void setRoom(RoomEntity room) { 
     this.room = room; 
    } 

} //ComputerEntity 

@Entity 
public class RoomEntity { 

    @Id 
    @GeneratedValue(generator="roomSeq",strategy= GenerationType.SEQUENCE) 
    @SequenceGenerator(name="roomSeq",sequenceName="SEQUENCEROOMID",allocationSize=1) 
    private long roomID; 

    @OneToMany(mappedBy = "room", cascade = {CascadeType.PERSIST, CascadeType.REMOVE}) 
    private Set<ComputerEntity> computers; 

    @javax.persistence.Column(name = "ROOMID") 
    public long getRoomID() { 
     return roomID; 
    } 

    public void setRoomID(long roomID) { 
     this.roomID = roomID; 
    } 

    public Set<ComputerEntity> getComputers() { 
     return computers; 
    } 

    public void setComputers(Set<ComputerEntity> computers) { 
     for(ComputerEntity computer : computers) { 
      computer.setRoom(this); 
     } 
     this.computers = computers; 
    } 
}//RoomEntity

當我試圖堅持一個新的房間用電腦就像這樣：

RoomEntity room = new RoomEntity(); 
    room.setAdministrator("Fox Moulder"); 
    room.setLocation("Area 51"); 

    ComputerEntity computer1 = new ComputerEntity(); 
    computer1.setDescription("Alienware area51 laptop"); 
    Set<ComputerEntity> computers = new HashSet<ComputerEntity>(); 
    computers.add(computer1); 

    room.setComputers(computers); 

    roomBean.createRoom(room);

roomBean是一個無狀態EJB和roomBean.createRoom簡單地調用entityManager.persist（室）。由於我在RoomEntity的計算機字段上有一個CascadeType.PERSIST，因此創建了ComptuerEntity。但是，如果我查看該ComputerEntity的房間字段，則會看到該房間字段爲空。因爲我有雙向關係，我會假設Eclipselink會自動填充房間。爲了有這樣的空間，我不得不添加

 for(ComputerEntity computer : computers) { 
      computer.setRoom(this); 
     }

to room.setComputers（...）。這是正確的方法還是有辦法讓Eclipselink自動設置它？

謝謝。 - NOAH

來源

2011-03-24 NBW

JPA中沒有關係維護。 EJB 2.1表明，通用關係管理的效率太低且麻煩。

我建議添加一個addComputer（）方法，該方法將在新添加的ComputerEntity上設置RoomEntity

來源

2011-03-24 18:12:42

的EclipseLink/JPA2多對一雙向級聯堅持問題

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