我为我的应用程序设计了一些表格,我已经放置了类似的内容:
product productversion
--- ---
productId productVersionId
productVersionId (ref) productId (ref)
name length
height
我们的关系一对多。我只需要一些带有参数的基础产品,这些参数可以更改和版本化参数,这样我就可以看到它的历史。现在......我有坚持这些对象的问题。我尝试了多种方法,这是最古老的方法:
Product p = new Product();
p.name = "some name";
Productversion pv = new Productversion();
pv.length = 10;
pv.height = 20;
p.productversionId = pv;
但是在尝试持久保存此对象时,我遇到的错误是productId不能为null,并且它引用了Productversion对象中的字段productId。我怎么能这样做?
[更新] 有关我的问题的更多信息:
public class Product implements Serializable {
@JoinColumn(name = "productversionId", referencedColumnName = "productversionId")
@ManyToOne(optional = true, cascade = CascadeType.PERSIST)
private Productversion productversionId;
@OneToMany(cascade = CascadeType.ALL, mappedBy = "productId")
private Collection<Productversion> productversionCollection;
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Basic(optional = false)
@Column(name = "ProductId")
private Integer productId;
@Basic(optional = false)
@NotNull
@Size(min = 1, max = 255)
@Column(name = "Name")
private String name = null;
// well I believe construct and getter/setter not important now
第二个实体:
public class Productversion implements Serializable {
@OneToMany(cascade = CascadeType.ALL, mappedBy = "productversionId")
private Collection<Productiondata> productiondataCollection;
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Basic(optional = false)
@Column(name = "productversionId")
private Integer productversionId;
@Basic(optional = false)
@NotNull
@Column(name = "parameter")
private float weight;
我创建新对象的方式(我不知道如何做到这一点):
public Product getNewProduct() {
if (newProduct == null) {
this.newProduct = new Product();
Productversion pv = new Productversion();
pv.setProductId(newProduct);
newProduct.setProductversionId(pv);
}
return newProduct;
}
我试图坚持反对的方式:
public Boolean addEntry(Product productData) {
Boolean status = false;
DbConnector dc = new DbConnector();
EntityManager em = dc.getEntityManager();
try {
EntityTransaction et = em.getTransaction();
et.begin();
em.persist(productData);
et.commit();
status = true;
} finally {
em.close();
}
return status;
}
答案 0 :(得分:0)
好像你在Product对象的id字段集上遗漏了。
Product p = new Product();
p.id = 1; <<<<<<-------------------
p.name = "some name";