当键是一个带有另一个实体列表的实体时，HashMap无法识别键

Question

我有一个电子商务类型的应用程序(Spring Boot(正在进行中，我正在使用HashMap<项目，长>以跟踪购物车中的商品和商品数量。当将项目添加到购物车时，hashmap不会识别类似的项目，而是创建一个新条目，而不是添加到项目计数中。我知道这在某种程度上与Jpa和hashcode的生成方式有关。我尝试了与POJO相同的情况(没有jpa或任何东西(，密钥被识别。我尝试覆盖equals(Object o(和hashCode((方法，如下所示(以忽略有问题的列表(，但它没有帮助，即使它现在生成了相同的hashCode(如下所示(。我很高兴能让这个工作，提前谢谢！

项目：

@Entity
@AllArgsConstructor
@NoArgsConstructor
public class Item extends AbstractPersistable<Long> {
private String name;
private Long productNumber;
private Double price;
private Double discountPrice;
private Double discountFactor;
private Integer stock;
@Column(length = 10000)
private String description;
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
private List<Image> images = new ArrayList<>();
private Boolean isHidden;
private Boolean isService;
@ManyToOne
private ItemCategory category;
public Item(String name, Double price, String description, int stock, ItemCategory category) {
this.name = name;
this.price = price;
this.description = description;
this.stock = stock;
this.category = category;
}
>>getters and setters<<

@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
Item item = (Item) o;
if (name != null ? !name.equals(item.name) : item.name != null) {
return false;
}
if (productNumber != null ? !productNumber.equals(item.productNumber) : item.productNumber != null) {
return false;
}
if (discountPrice != null ? !discountPrice.equals(item.discountPrice) : item.discountPrice != null) {
return false;
}
if (discountFactor != null ? !discountFactor.equals(item.discountFactor) : item.discountFactor != null) {
return false;
}
if (stock != null ? !stock.equals(item.stock) : item.stock != null) {
return false;
}
if (description != null ? !description.equals(item.description) : item.description != null) {
return false;
}
if (isHidden != null ? !isHidden.equals(item.isHidden) : item.isHidden != null) {
return false;
}
if (isService != null ? !isService.equals(item.isService) : item.isService != null) {
return false;
}
return category != null ? category.equals(item.category) : item.category == null;
}
@Override
public int hashCode() {
int result = name != null ? name.hashCode() : 0;
result = 31 * result + (productNumber != null ? productNumber.hashCode() : 0);
result = 31 * result + (discountPrice != null ? discountPrice.hashCode() : 0);
result = 31 * result + (discountFactor != null ? discountFactor.hashCode() : 0);
result = 31 * result + (stock != null ? stock.hashCode() : 0);
result = 31 * result + (description != null ? description.hashCode() : 0);
result = 31 * result + (isHidden != null ? isHidden.hashCode() : 0);
result = 31 * result + (isService != null ? isService.hashCode() : 0);
result = 31 * result + (category != null ? category.hashCode() : 0);
return result;
}

图片：

@Entity
@AllArgsConstructor
@NoArgsConstructor
@Data
public class Image extends AbstractPersistable<Long> {
@Lob
@Basic(fetch = FetchType.LAZY)
private byte[] content;
@ManyToOne
@JoinColumn(name = "item_id")
private Item item;
private Boolean isMainPicture;
private int ordinal;
}

购物车：

@Component
@AllArgsConstructor
@NoArgsConstructor
@Data
@Scope(value = "session", proxyMode = ScopedProxyMode.TARGET_CLASS)
public class ShoppingCart {
private Map<Item, Long> items = new HashMap<>();
public void addToCart(Item item) {
Long itemCount = this.items.getOrDefault(item, 0L) + 1L;
this.items.put(item, itemCount);
}
public void removeFromCart(Item item) {
if (this.items.get(item) == 1L) {
this.items.remove(item);

return;
}
Long itemCount = this.items.get(item) - 1L;
this.items.put(item, itemCount);
}
public Double getSum() {
return this.items.keySet().stream()
.map(item -> (item.getPrice() * this.items.get(item)))
.reduce(0.0, (currentSum, nextCost) -> currentSum + nextCost);
}
}

@Controller:中的viewCart方法

@GetMapping("/cart")
public String viewCart(Model model) {
System.out.println("!!!!!!!!!!!!!!!!!!");
shoppingCart.getItems().keySet().stream().forEach(key -> System.out.println(key.toString() + "; hashcode = " + key.hashCode()));
model.addAttribute("items", shoppingCart.getItems());
return "cart";
}

viewCart方法之后的控制台，HashMap中有两个类似的项目：

!!!!!!!!!!!!!!!!!!
Entity of type mortar.euroshopper.eCommerceApplication.Item with id: 6; hashcode = 34943583
Entity of type mortar.euroshopper.eCommerceApplication.Item with id: 6; hashcode = 34943583

Answer 1

感谢M.Deinum对解决问题的评论！此处提供的说明：https://vladmihalcea.com/the-best-way-to-implement-equals-hashcode-and-tostring-with-jpa-and-hibernate/