Question

使用Netbeans开发嵌入式数据库应用程序（Derby）。我想弄清楚多对多的关系是如何运作的。 Netbeans为我创建了实体类。我理解如何检索记录并将新结果提交给记录，但我不熟悉如何提交“集合”，请参阅下面的代码。

@Entity
@Table(name = "MASTER")
@XmlRootElement
@NamedQueries({....
})
public class Master implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Basic(optional = false)
@Column(name = "ID")
private Integer id;
@Column(name = "SDS_NUMBER")
private Integer sdsNumber;
@Column(name = "PRODUCT_NAME")
private String productName;
@Column(name = "PRODUCT_DESCRIPTION")
private String productDescription;
@Column(name = "SDS_FILE_NAME")
private String sdsFileName;
@Column(name = "USE_STATUS")
private Boolean useStatus;
@Column(name = "DATA_UPDATED")
@Temporal(TemporalType.DATE)
private Date dataUpdated;
@Column(name = "PROPER_SHIPPING_NAME")
private String properShippingName;
@Column(name = "SIGNAL_WORD")
private String signalWord;
@Column(name = "GHS_COMPLIANT")
private Boolean ghsCompliant;
@JoinTable(name = "STATEMENT_LOOKUP", joinColumns = {
    @JoinColumn(name = "SDS_NUMBER", referencedColumnName = "SDS_NUMBER")},
     inverseJoinColumns = {
    @JoinColumn(name = "STATEMENT_ID", referencedColumnName = "STATEMENT_ID")})
@ManyToMany
private Collection<Statements> statementsCollection;
@ManyToMany(mappedBy = "masterCollection")
private Collection<Manufacturers> manufacturersCollection;
@JoinTable(name = "PICTOGRAM_LOOKUP", joinColumns = {
    @JoinColumn(name = "SDS_NUMBER", referencedColumnName = "SDS_NUMBER")}, inverseJoinColumns = {
    @JoinColumn(name = "PICTOGRAM_ID", referencedColumnName = "PICTOGRAM_ID")})
@ManyToMany
private Collection<Pictograms> pictogramsCollection;
@ManyToMany(mappedBy = "masterCollection")
private Collection<Locations> locationsCollection;
@ManyToMany(mappedBy = "masterCollection")
private Collection<Keywords> keywordsCollection;

public Master() {
}

public Master(Integer id) {
    this.id = id;
}  Getters and Setters follow.......
    @XmlTransient
public Collection<Keywords> getKeywordsCollection() {
    return keywordsCollection;
}

public void setKeywordsCollection(Collection<Keywords> keywordsCollection) {
    this.keywordsCollection = keywordsCollection;
}


public class NewClass {
public static void main(String[] args) {
EntityManagerFactory entityManagerFactory = 
Persistence.createEntityManagerFactory("JavaApplication20PU");
EntityManager em = entityManagerFactory.createEntityManager();
EntityTransaction userTransaction = em.getTransaction();

userTransaction.begin();
Master record = new Master();
record.setProductName("Test Product Name");
record.setProductDescription("Test Product Description");
record.setProperShippingName("Proper shipping name test");
record.setSdsNumber(999);
record.setSignalWord("WARNING");
record.setUseStatus(false);
record.setGhsCompliant(false);
record.setKeywordsCollection();// This is where I need help!
em.persist(record);
userTransaction.commit();
em.close();
entityManagerFactory.close();
}
}

以上是我的测试类中填充记录的代码。注释行是我需要帮助的地方。最终，这需要从Jlist中选择，但任何通用的帮助或链接到某个地方，我可以更好地了解如何工作将不胜感激。谢谢！

Answer 1

考虑本教程是一个很好的例子，你可以看到DER的一些工作示例。

Tutorial

并且它不是Jlist它是List或ArrayList，可能是拼写错误XD。在您的测试中，您没有向主人添加关键字列表。

Javax持久性多对多EclipseLink JPA 2.1

1 个答案: