如何在休眠中加載子對象

Question

加載父對象（DuaVO）對象時，如何加載子對象（RefAuthorizationVO）。

主類方法裝入

DuaVO dua = (DuaVO) session.get(DuaVO.class, "1"); 

RefAuthorization兒童

@Entity 
@Table(name = "RFRNC_AUTHRZTN") 
public class RefAuthorizationVO implements Serializable 
{ 
    @Column(name = "SYS_CREAT_USER_ID") 
    private String sysCreatedUserId; 

    @Column(name = "SYS_CREAT_TS") 
    private Date sysCreatedTimestamp; 

    @Column(name = "SYS_UPDT_USER_ID") 
    private String sysUpdateUserId; 

    @Column(name = "SYS_UPDT_TS") 
    private Date sysUpdateTimestamp; 

    @Id 
    @GeneratedValue(strategy = GenerationType.AUTO) 
    @Column(name="AUTHRZTN_CD") 
    private String authorizationCode; 

    @Column(name="AUTHRZTN_DESC") 
    private String authorizationDescription; 

DuaVO父

@Entity 
@Table(name = "DUA") 
public class DuaVO implements java.io.Serializable { 

    @Id 
    @Column(name= "DUA_NUM") 
    private String duaNumber; 

    // AuditDetails 

    @Column(name = "SYS_CREAT_USER_ID") 
    private String sysCreatedUserId; 

    @Column(name = "SYS_CREAT_TS") 
    private Date sysCreatedTimestamp; 

    @Column(name = "SYS_UPDT_USER_ID") 
    private String sysUpdateUserId; 

    @Column(name = "SYS_UPDT_TS") 
    private Date sysUpdateTimestamp; 

    @Column(name = "DUA_SHRT_DESC") 
    private String duaShortDesc; 

    @Column(name = "AUTHRZTN_CD") 
    private String authorizationCode; 

    @ManyToOne 
    private RefAuthorizationVO refAuthorizationVO; 

    } 

但是，當我嘗試訪問像這樣的孩子時。

System.out.println("Ref Auth: " + dua.getRefAuthorizationVO()); 

我得到空。

Answer 1

想你錯過@JoinColumn註解

@JoinColumn(name = "FK_ID", referencedColumnName = "ID") 
@ManyToOne