Java JPA - 持久连接表

时间:2014-09-18 10:54:59

标签: mysql hibernate jpa one-to-many

HY!

这让我疯狂了几天......希望有人可以帮助我。

情况:

我有一个简单的 datamodel ,有三个表:

  • 产品(sa_s_prod)
  • 组件(sa_s_comp)
  • CompProd(sa_l_compprod - 这是产品和组件的连接表)

enter image description here

联接表(CompProd)有其他列。

我的(已剥离)实体如下:

@Entity
@Table(name = "sa_s_comp")
public class SComp implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int compId;
@Column(unique = true, nullable = false, length = 50)
private String compName;
@Column(length = 50)
private String compDesc;
@Column(nullable = false)
private Boolean compIsOnAvailability;
@Min(value = 0)
@Column(nullable = false)
private int compIndex;
@Column(nullable = false)
private Lkzs lkz;
@Column(nullable = false)
@Temporal(TemporalType.TIMESTAMP)
private Date cdate;
@Column(nullable = false)
private String cuser;

@NotNull
@OneToOne(optional = false)
@JoinColumn(name = "compgroupId", nullable = false)
private SCompGroup group;

@OneToMany(mappedBy = "component", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
private List<LCompProd> products;

@OneToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "transId", unique = true, nullable = true)
private STrans translation;

...

/**
 * Adds the given product to the list of assigned products for this
 * component.
 *
 * @param prod
 *            the product to be assigned
 * @return the component
 */
public void addProduct(SProd prod) {
if (this.products == null)
    this.products = new ArrayList<LCompProd>();
LCompProd compprod = new LCompProd(this, prod);
this.products.add(compprod);
compprod.setComponent(this);
}

....

@Entity
@Table(name = "sa_s_prod")
public class SProd implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int prodId;
@NotNull
private Product.Type prodType;
@NotNull
private String prodName;
private String prodDesc;
private BigDecimal prodQuantityDef;
private Globals.Units prodUnitDef;
private Lkzs lkz;
@Temporal(TemporalType.TIMESTAMP)
private Date cdate;
private String cuser;

@OneToOne(optional = false)
@JoinColumn(name = "subcatId", nullable = false)
private SSubCat subcat;

@OneToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "transId", unique = true)
private STrans translation;

@OneToMany(mappedBy = "product", fetch = FetchType.EAGER)
private List<LCompProd> components;

....

@Entity
@IdClass(LCompProdId.class)
@Table(name = "sa_l_compprod")
public class LCompProd implements Serializable {

@Id
private int compId;
@Id
private int prodId;

@ManyToOne(optional = false, fetch = FetchType.EAGER)
@JoinColumn(name = "compId", insertable = false, updatable = false)
private SComp component;

@ManyToOne(optional = false, fetch = FetchType.EAGER)
@JoinColumn(name = "prodId", insertable = false, updatable = false)
private SProd product;

@NotNull
private Lkzs lkz;
@Temporal(TemporalType.TIMESTAMP)
private Date cdate;
private String cuser;

....

public class LCompProdId implements Serializable {

private int compId;
private int prodId;
....

使用此代码,我可以毫无问题地检索组件和相关产品。但是我不能坚持到联接表(CompProd)。即使没有与两个独立的人持续不断地进行这样做。

问题是外键约束失败,因为在持久化期间未在“连接数据对象”中设置组件的主键(compId)。

也许这是设置主/外键的“正常”行为,但我不能相信hibernate无法处理这个简单的事情?! (希望我是对的; - )

我阅读了很多文章和博客,尝试了不同的方法,但仍然无法使其发挥作用(以某种方式应该实施)。

任何帮助表示赞赏。 THX。

PS:我正在使用JPA2(Hibernate)。

1 个答案:

答案 0 :(得分:0)

您似乎在 SComp SProd 对象创建中获得 compId prodId 值。

如何将生成的id传播到 LCompProd 实体?您确定从中获取值的对象是托管实体吗?

例如,如果使用merge调用创建对象,则该参数不会成为托管实体。因此,您不应直接获得生成的Id。你可以通过方法调用的结果得到它。