java - 刷新 JPA 实体时出错

Question

我有以下领域模型

Currency ----< Price >---- Product

或英文

A Product has one or more Prices. Each Price is denominated in a particular Currency.

Price 有一个复合主键(由下面的 PricePK 表示)，它由 Currency 和 Product 的外键组成。 JPA 注释的 Java 类的相关部分如下(大部分省略了 getter 和 setter):

@Entity @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Currency {

    @Id 
    private Integer ix;

    @Column 
    private String name;

    @OneToMany(mappedBy = "pricePK.currency", cascade = CascadeType.ALL, orphanRemoval = true)
    @LazyCollection(LazyCollectionOption.FALSE)
    private Collection<Price> prices = new ArrayList<Price>();
}

@Entity @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Product {

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

    @OneToMany(mappedBy = "pricePK.product", cascade = CascadeType.ALL, orphanRemoval = true)
    @LazyCollection(LazyCollectionOption.FALSE)
    private Collection<Price> defaultPrices = new ArrayList<Price>();
}

@Embeddable
public class PricePK implements Serializable {

    private Product product;    
    private Currency currency;

    @ManyToOne(optional = false)
    public Product getProduct() {
        return product;
    }

    @ManyToOne(optional = false)
    public Currency getCurrency() {
        return currency;
    }    
}

@Entity @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Price {

    private PricePK pricePK = new PricePK();

    private BigDecimal amount;

    @Column(nullable = false)
    public BigDecimal getAmount() {    
        return amount;
    }

    public void setAmount(BigDecimal amount) {    
        this.amount = amount;
    }

    @EmbeddedId
    public PricePK getPricePK() {
        return pricePK;
    }    

    @Transient
    public Product getProduct() {
        return pricePK.getProduct();
    }

    public void setProduct(Product product) {
        pricePK.setProduct(product);
    }

    @Transient
    public Currency getCurrency() {
        return pricePK.getCurrency();
    }

    public void setCurrency(Currency currency) {
        pricePK.setCurrency(currency);
    }
}

当我尝试 refresh Product 的一个实例，我得到一个 StackOverflowError，所以我怀疑上面的映射中存在某种循环(或其他错误)，有人能发现吗？

Answer 1

我见过几次这个错误，但我不记得确切的解决方案。我认为您需要从 PricePK(@ManyToOne)中删除映射并将其替换为价格上的@AssociationOverrides。

@Entity @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
@AssociationOverrides({
    @AssociationOverride(name = "pricePK.product", 
                         joinColumns = @JoinColumn(name = "product_id")),
    @AssociationOverride(name = "pricePK.currency", 
                         joinColumns = @JoinColumn(name = "currency_id"))
})
public class Price extends VersionedEntity {
    [...]
}

请检查列名是否正确，因为我在 Product 或 Currency 上看不到 id 列。