使用条件生成器进行动态查询:一对多

Question

我想使用 CriteriaBuilder 和 Predicate 构建一个查询，它将仅返回那些具有"图像"的产品的列表。但鉴于产品和图像@OneToMany之间存在关系，我不知道如何实现它。例如，使用 JpaRepository，我知道这个查询可以这样构造：List<Product> findAllByImagesIsNotNull().

但是我需要一个动态查询，所以据我了解，最好使用CriteriaBuilder。

所以，我有两个实体：

@Entity
@Table(name = "products")
public class Product {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
long id;
@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
@JoinColumn(name = "product_details_id")
ProductDetails productDetails;
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "category_id")
Category category;
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "lens_color_id")
LensColor lensColor;
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "frame_color_id")
FrameColor frameColor;
@OneToMany(fetch = FetchType.LAZY,
cascade = CascadeType.ALL,
orphanRemoval = true)
List<Image> images = new ArrayList<>();
@Column(unique = true)
String productNumber;
}

和

@Entity
@Table(name = "images")    
public class Image {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
Long id;
String imageName;
String imageType;
boolean isMainImage;
}

我有两个元模型：

@StaticMetamodel(Product.class)
public abstract class Product_ {
public static volatile SingularAttribute<Product, LensColor> lensColor;
public static volatile ListAttribute<Product, Image> images;
public static volatile SingularAttribute<Product, FrameColor> frameColor;
public static volatile SingularAttribute<Product, Long> id;
public static volatile SingularAttribute<Product, String> productNumber;
public static volatile SingularAttribute<Product, ProductDetails> productDetails;
public static volatile SingularAttribute<Product, Category> category;
}

和

@StaticMetamodel(Image.class)
public abstract class Image_ {
public static volatile SingularAttribute<Image, String> imageName;
public static volatile SingularAttribute<Image, Boolean> isMainImage;
public static volatile SingularAttribute<Image, Long> id;
public static volatile SingularAttribute<Image, String> imageType;
}

这是我的查询代码：

public List<Product> findByCriteria(Integer minPrice, Integer maxPrice, List<LensColor> lensColor, List<FrameColor> frameColor) {
return productDAO.findAll(new Specification<Product>() {
@Override
public Predicate toPredicate(Root<Product> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) {
Join<Product, ProductDetails> productDetailsJoin = root.join(Product_.productDetails, JoinType.INNER);
List<Predicate> predicates = new ArrayList<>();
// MY PREDICATE CODE FOR FIND ALL PRODUCTS WITH IMAGES IS NOT NULL
if (!CollectionUtils.isEmpty(lensColor)) {
predicates.add(criteriaBuilder.and(root.get("lensColor").in(lensColor)));
}
if (!CollectionUtils.isEmpty(frameColor)) {
predicates.add(criteriaBuilder.and(root.get("frameColor").in(frameColor)));
}
if (minPrice != null && maxPrice != null) {
predicates.add(criteriaBuilder.between(productDetailsJoin.get(ProductDetails_.price), minPrice, maxPrice));
}
return criteriaBuilder.and(predicates.toArray(new Predicate[predicates.size()]));
}
});
}

Answer 1

对于 * 对多关系，请根据集合类型使用PluralJoin，类型为：

Join<Product, Image> joinImages = root.joinList("images", JoinType.INNER);
predicates.add(cb.isNotNull(joinImages.get(Image_.id)));