OneToOne外键保存问题

Question

@Entity 
    @Table(name = "applicant") 
    public class Applicant implements Serializable { 

     private static final long serialVersionUID = -8634638904962909584L; 

     // Primary id required by Hibernate 
     @Id 
     @GeneratedValue(strategy=IDENTITY) 
     @Column(name = "applicant_id", nullable=false, unique=true) 
      private Long applicantId; // Unique id for each applicant 

     @OneToOne(cascade = CascadeType.ALL) 
     @Fetch(value = FetchMode.SELECT) 
     @JoinColumn(name = "applicant_id", referencedColumnName= "applicant_id") 
     private DS1350 ds1350; 


     public Applicant() { 

     } 

    } 

    @Entity 
    @Table(name = "ds_1350") 

    public class DS1350 implements Serializable { 
     private static final long serialVersionUID = -7370747595057569296L; 

     // Primary id required by Hibernate 
     @Id 
     @GeneratedValue(strategy=IDENTITY) 
     @Column(name = "ds_1350_id", nullable=false, unique=true) 
     private Long ds1350Id; 

     @Column(name = "applicant_id", unique=true, nullable=false) 
    // @GeneratedValue(generator="gen") 
    // @GenericGenerator(name = "gen", strategy = "foreign", parameters = @Parameter(name = "property", value = "applicant")) 
     private Long applicantId; // Unique id for each applicant 

     @Column(name = "ds1350_no", length = 50) 
     private String ds1350Number; 

    } 

    public class ApplicantDaoTest { 
     @Autowired 
     private ApplicantDao applicantDao; 

     private Applicant applicant; 
     private DS1350 ds1350 = new DS1350(); 

     @BeforeClass 
     public static void beforeClass() { 
     } 


     @AfterClass 
     public static void afterClass() { 
     } 


     @Before 
     public void setup() { 
      this.initApplicant(); 
     } 

     @After 
     public void teardown() { 
     } 

     private void initApplicant() { 
      applicant = new Applicant(); 

      applicant.setFirstName("John"); 

      Calendar calendar = Calendar.getInstance(); 
      applicant.setDob(calendar); 

      applicant.setSsn("123456789"); 
      applicant.setCreatedBy("JUNIT"); 
      applicant.setCreatedDate(Calendar.getInstance()); 
      applicant.setModifiedBy("JUnit"); 
      applicant.setModifiedDate(Calendar.getInstance()); 

      this.initDS1350(); 

     } 


     private void initDS1350() {   
      ds1350.setDs1350Number("ds1350Number"); 
      ds1350.setCreatedBy("JUNIT"); 
      ds1350.setCreatedDate(Calendar.getInstance()); 

      applicant.setDs1350(ds1350); 
     } 

     @Test 
     public void testSaveApplicant() { 
      Long applicantId = applicantDao.saveApplicant(applicant); 
      applicant = applicantDao.getApplicantByPrimaryKey(applicantId); 
      assertTrue("ds1350Number".equals(applicant.getDs1350().getDs1350Number())); 
     } 
    } 

以下是ds1350和申请人类的代码。我使用hibernate session save（）来保存ds1350包含在申请人对象中的申请人。我有OneToMany，这是完美的，但这OneToOne不工作。 applicant.getDs1350（）抛出一个NullPointerException异常，因为外键（ds1350中的applicant_id）保存为null，而applicantsDao.getApplicantByPrimaryKey（applicantId）无法获取ds1350对象。

Answer 1

摆脱“@Fetch（value = FetchMode.SELECT）”。你告诉它在你的OneToOne注解中急切地获取，但是告诉它用@Fetch注解来获取懒惰。

此外，请确保ds1350字段上的加入列具有引用正确的FK字段（如果申请人中的字段未被称为id）。

@OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL) 
@JoinColumn(name = "applicant_id", referencedColumnName= "applicant_id") 
private DS1350 ds1350; 

，我错过了在第一另一点是，你使用

@GeneratedValue(strategy=IDENTITY) 

引述​​3210： “指示的持久性提供者必须使用数据库身份分配为实体主键柱。”

如果您在创建链接时没有手动分配该创意，则该ID不会被保留。使用@GeneratedValue（strategy = AUTO）将告诉数据库它需要为您的子类（DS1350）生成ID。这是一个修正，但可能不是你要做的。

此外，根据您的更新你引用的连接列从ds1350错误的外键，而联想到你的申请看起来可疑，尝试这样的事情：

//in applicant 
    @OneToOne(cascade = CascadeType.ALL) 
    @Fetch(value = FetchMode.SELECT) 
    @JoinColumn(name = "ds1350_id", referencedColumnName= "applicant_id") 
    private DS1350 ds1350; 

    //in ds1350 
    @OneToOne(mappedBy="applicant", cascade=CascadeType.ALL) 
    private Applicant applicant; // Unique id for each applicant 

我的天堂”吨测试了这一点。