问保存具有缓存对象的实体会导致分离实体异常。

EN

@Entity
@DynamicInsert
@DynamicUpdate
@Table(name = "ad")
public class Ad implements SearchableAdDefinition {

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

    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    private User user;

    @OneToMany(mappedBy = "ad", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    private Set<AdAttribute> adAttributes;

(.....) }

@Entity
@Table(name = "attrib_ad")
@IdClass(CompositeAdAttributePk.class)
public class AdAttribute {

    @Id
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "ad_id")
    private Ad ad;

    @Id
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "attrib_id")
    private Attribute attribute;

    @Column(name = "value", length = 75)
    private String value;

    public Ad getAd() {
        return ad;
    }

    public void setAd(Ad ad) {
        this.ad = ad;
    }

    public Attribute getAttribute() {
        return attribute;
    }

    public void setAttribute(Attribute attribute) {
        this.attribute = attribute;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }
}


@Embeddable
 class CompositeAdAttributePk implements Serializable {
    private Ad ad;
    private Attribute attribute;

    public CompositeAdAttributePk() {

    }

    public CompositeAdAttributePk(Ad ad, Attribute attribute) {
        this.ad = ad;
        this.attribute = attribute;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        CompositeAdAttributePk compositeAdAttributePk = (CompositeAdAttributePk) o;
        return ad.getId().equals(compositeAdAttributePk.ad.getId()) && attribute.getId().equals(compositeAdAttributePk.attribute.getId());

    }

    @Override
    public int hashCode() {
        return Objects.hash(ad.getId(), attribute.getId());
    }

}

@Cacheable(value = "requiredAttributePerCategory", key = "#category.id")
public List<CategoryAttribute> findRequiredCategoryAttributesByCategory(Category category) {

    return categoryAttributeRepository.findCategoryAttributesByCategoryAndAttribute_Required(category, 1);
}

@Transactional
public Ad create(String title, User user, Category category, AdStatus status, String description, String url, Double price, AdPriceType priceType, Integer photoCount, Double minimumBid, Integer options, Importer importer, Set<AdAttribute> adAtributes) {
    //Assert.notNull(title, "Ad title must not be null");

    Ad ad = adCreationService.createAd(title, user, category, status, description, url, price, priceType, photoCount, minimumBid, options, importer, adAtributes);

    for (AdAttribute adAttribute : ad.getAdAttributes()) {
        adAttribute.setAd(ad);

/* If I add this here, I don't face any exception, but then I don't take benefit from using cache:
        Attribute attribute = attributeRepository.findById(adAttribute.getAttribute().getId()).get();
        adAttribute.setAttribute(attribute);
*/

    }

    ad = adRepository.save(ad);

    solrAdDocumentRepository.save(AdDocument.adDocumentBuilder(ad));

    return ad;
}