Question

我遇到OneToMany关系的问题。我试图获取列表，但它没有检索任何东西。论文是我的资料来源：

这是主要的：

        public class ModelTest {


        public static void main(String[] args) {

           //Creating 
           {
               StudyEntity st = new StudyEntity();       
               st.setPatientName("Edwin");
               st.setStudy_pk("111");           
               new StudyCRUD().create(st);



               StudyEntity st2 = new StudyEntity();
               st2.setPatientName("Jose");
               st2.setStudy_pk("2333");
               new StudyCRUD().create(st2); // Persist the object in DB



               SeriesEntity se = new SeriesEntity();
               se.setSeries_iuid("44444");
               se.setStudyentity(st);
               new SeriesCRUD().create(se);



               SeriesEntity se2 = new SeriesEntity();
               se2.setStudyentity(st);




               new SeriesCRUD().create(se2); // Persist the object in DB
           }

           //Retrieving
           {
               StudyEntity study = new SeriesCRUD().getStudyEntityByID(1); // Get a Object    by ID 
               System.out.println("Name: "+study.getPatientName());
               System.out.println("Size: "+study.getStudySeries().size());
           }



        }

    }

结果

姓名：Edwin
大小：0

表信息：

studyentity

       ida, DELETED, MODALITY, PATIENTNAME, SENT, STUDY_DATETIME, STUDY_ID, STUDY_PK<br />
       1, 0, '', 'Edwin', 0, '', '', '111'<br />
       2, 0, '', 'Jose', 0, '', '', '2333'<br />

seriesentity

       ID, SERIES_IUID, SERIES_PK, ida
       1, '', '', 1
       2, '', '', 1

实体表：

studyentity

    @Entity @Table(name="studyentity")
    public class StudyEntity implements Serializable{

    @Id @GeneratedValue(strategy=GenerationType.IDENTITY) @Column(name="ida")
    private long id;

    private String patientName;
    private String study_id;

    private String modality;

    @Column(unique=true )
    private String study_pk;

    @Temporal(javax.persistence.TemporalType.TIMESTAMP)
    private Date study_datetime;

    private boolean sent;

    @Column(columnDefinition="boolean default false")
    private boolean deleted;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY,mappedBy="studyentity")
    private List<SeriesEntity> studySeries;

    //getters and setters

seriesentity

    @Entity @Table(name="seriesentity")
    public class SeriesEntity implements Serializable {


    private static final long serialVersionUID = 1L;

    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "ida", nullable = false)    
    private StudyEntity studyentity;

    private String series_pk;

    private String series_iuid;

    //Getters and Setters

Answer 1

JPA不会为您维护关系。除非您将seriesEntity实例添加到studyEntity的集合中，否则除非您强制刷新，否则它不会存在。最好的做法是在创建实体时在实体中设置双向关系的两侧，然后强制数据库命中以便稍后修复它。

[JPA，eclipselink]一对多关系没有抓住孩子

1 个答案: