我從這里擴(kuò)展我的問(wèn)題：Define CompositeKey with three tables using JPA/Hibernate? . 在此示例中，我希望創(chuàng)建復(fù)合鍵以創(chuàng)建 PRODUCT_ID、CATEGORY_ID、STOCK_ID 的唯一組合。我開發(fā)了以下代碼，但不確定如何將記錄保存到數(shù)據(jù)庫(kù)中。Stock.java@Entitypublic class Stock implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = IDENTITY) @Column(name = "STOCK_ID", unique = true, nullable = false) private Integer stockId; @Column(name = "STOCK_CODE", unique = true, nullable = false, length = 10) private String stockCode; @Column(name = "STOCK_NAME", unique = true, nullable = false, length = 20) private String stockName; // Owner of the relationship @OneToMany(fetch = FetchType.LAZY, mappedBy = "linkPk.stock", cascade = CascadeType.ALL) private Set<StockCategoryProductLink> stockCategoryProductLinks = new HashSet<>(0); public Stock() { } public Stock(Integer stockId, String stockCode, String stockName, Set<StockCategoryProductLink> stockCategoryProductLinks) { super(); this.stockId = stockId; this.stockCode = stockCode; this.stockName = stockName; this.stockCategoryProductLinks = stockCategoryProductLinks; } public Integer getStockId() { return stockId; } public void setStockId(Integer stockId) { this.stockId = stockId; } public String getStockCode() { return stockCode; } public void setStockCode(String stockCode) { this.stockCode = stockCode; } public String getStockName() { return stockName; } public void setStockName(String stockName) { this.stockName = stockName; } public Set<StockCategoryProductLink> getStockCategoryProductLinks() { return stockCategoryProductLinks; } public void setStockCategoryProductLinks(Set<StockCategoryProductLink> stockCategoryProductLinks) { this.stockCategoryProductLinks = stockCategoryProductLinks; }}
1 回答
Qyouu
TA貢獻(xiàn)1786條經(jīng)驗(yàn) 獲得超11個(gè)贊
好吧，我知道你說(shuō)的是什么，但我認(rèn)為這不是你的意思。你說(shuō)
實(shí)際上我有三個(gè)表，Stock、Category 和 Product。
@ManyToManyStock 和 Category 之間的關(guān)系，以及@ManyToManyCategory 和 Product 之間的關(guān)系。
這有助于抽象地思考這個(gè)問(wèn)題。在陳記法中你說(shuō)的是
但是，這可能不是您的意思。這是有問(wèn)題的，因?yàn)槟枰?code>Category為每個(gè)Stock和Product關(guān)系創(chuàng)建一個(gè)新實(shí)體。因此，如果您有一個(gè) ETF 類別，那么它將針對(duì) BobsBestETF 產(chǎn)品中的每只股票進(jìn)行復(fù)制，實(shí)際上是針對(duì)每個(gè)實(shí)例化關(guān)系進(jìn)行復(fù)制。
你的意思可能更像是 a StockandProduct與Category屬性的關(guān)系，就像這樣。
這允許許多產(chǎn)品，每個(gè)產(chǎn)品都有很多庫(kù)存，每個(gè)產(chǎn)品/庫(kù)存關(guān)系都有一個(gè)特定的類別屬性。您將遇到的問(wèn)題是您不想Category成為一個(gè)屬性，而是一個(gè)類別查找表，如下所示：
我認(rèn)為這就是您要找的。使用復(fù)合 ID 實(shí)現(xiàn)這應(yīng)該相當(dāng)簡(jiǎn)單，但您顯示的示例似乎有些過(guò)時(shí)或不清楚。最好找到更好的例子。這就是我為最后一個(gè)模式建模的方式。
@Entity
public class Stock {
@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
}
@Entity
@Data
public class Product {
@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
}
@Entity
public class Category {
@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
}
@Entity
@Data
public class StockProduct {
@EmbeddedId
private StockProductPk id;
@ManyToOne
@MapsId("productId")
private Product product;
@ManyToOne
@MapsId("stockId")
private Stock stock;
@ManyToOne
private Category category;
}
@Embeddable
@Data
public class StockProductPk implements Serializable {
private static final long serialVersionUID = 1L;
private Long stockId;
private Long productId;
}
并作為使用它的示例：
private void create() {
Category catEtf = new Category();
categoryRepo.save(catEtf);
Stock s1 = new Stock();
stockRepo.save(s1);
Product bobEtfs = new Product();
productRepo.save(bobEtfs);
// create a relationship
StockProduct bs1 = new StockProduct();
bs1.setId(new StockProductPk());
bs1.setProduct(bobEtfs);
bs1.setStock(s1);
bs1.setCategory(catEtf);
stockProductRepo.save(bs1);
}
private void read() {
StockProduct sp1 = new StockProduct();
Product p1 = new Product();
p1.setId(1L);
sp1.setProduct(p1);
List<StockProduct> bobEtfs = stockProductRepo.findAll(Example.of(sp1, ExampleMatcher.matching()));
System.out.println(bobEtfs);
}
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