Java 在Spring中使用类进行查询

我正在尝试做这个查询

列出findProductByCategory\u CategoryNameAndPriceBetween（字符串类别、双最小值、双最大值）

但是查询返回的是一个空列表。我做错了什么？我还尝试在类别和类别名称之间不使用下划线。这是类别和产品：

@Entity
public class Category {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="ID")
    private Long id;

    @Column(name = "NAME")
    private String categoryName;
    
    @OneToMany(mappedBy = "category", fetch = FetchType.EAGER)
    private List<Product> products;

...
}

这就是我实现存储库的方式：

@Repository
public interface ProductDao extends JpaRepository<Product,Long> {
...

@存储库
公共接口产品DAO扩展了JpaRepository{
...
根据您的方法应该是：

List<Product> findProductByCategoryNameAndPriceBetween(String category, double min, double max)

列出findProductByCategoryNameAndPriceBetween（字符串类别、双最小值、双最大值）

假设categoryName和price是在Category类中定义的。
使用下面的实现，您的查询就可以了

请注意，我添加了一个替代实现：

List<Product> findByCategoryAndPriceBetween(Category category, double min, double max);

产品类别

package no.mycompany.myapp.misc;

import lombok.Getter;
import lombok.Setter;

import javax.persistence.*;

// cannot use @Data here because of circular ref
@Getter
@Setter
@Entity
@Table(name="PRODUCT")
public class Product {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="ID")
    private Long id;

    @Column(name="PRICE")
    private Double price;

    @Column(name="BRAND")
    private String brand;

    @Column(name="MODEL")
    private String model;

    //@Lob
    @Column(name="DESCRIPTION")
    private String description;

    @Column(name = "IMAGE_URL")
    private String imageUrl;

    @ManyToOne
    @JoinColumn(name = "CATEGORY_ID", referencedColumnName = "ID")
    private Category category;
}

产品刀

public interface ProductDao extends JpaRepository<Product, Long> {
    List<Product> findProductByCategory_CategoryNameAndPriceBetween(String category, double min, double max);
    List<Product> findByCategoryAndPriceBetween(Category category, double min, double max);
}

请同时发布您的JPA类！我在任何地方都看不到价格。请注意，第一步通常是确认它们符合您期望的逻辑。价格在类别产品中，而categoryName在类别类中
package no.mycompany.myapp.misc;

import lombok.Getter;
import lombok.Setter;

import javax.persistence.*;

// cannot use @Data here because of circular ref
@Getter
@Setter
@Entity
@Table(name="PRODUCT")
public class Product {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="ID")
    private Long id;

    @Column(name="PRICE")
    private Double price;

    @Column(name="BRAND")
    private String brand;

    @Column(name="MODEL")
    private String model;

    //@Lob
    @Column(name="DESCRIPTION")
    private String description;

    @Column(name = "IMAGE_URL")
    private String imageUrl;

    @ManyToOne
    @JoinColumn(name = "CATEGORY_ID", referencedColumnName = "ID")
    private Category category;
}

public interface ProductDao extends JpaRepository<Product, Long> {
    List<Product> findProductByCategory_CategoryNameAndPriceBetween(String category, double min, double max);
    List<Product> findByCategoryAndPriceBetween(Category category, double min, double max);
}

package no.mycompany.myapp.misc;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;
import org.springframework.test.context.ActiveProfiles;

import static org.assertj.core.api.AssertionsForClassTypes.assertThat;

@DataJpaTest
public class ProductDaoTest {

    @Autowired
    ProductDao productDao;

    @Autowired
    TestEntityManager testEntityManager;

    @Test
    public void findByCategoryAndPriceBetween_singleCategoryWithSingleProductInDb_expectSingleProduct() {
        var category = createCategoryWithSingleProduct();
        testEntityManager.persist(category);
        var result = productDao.findByCategoryAndPriceBetween(category, 0.0, 2.0);
        assertThat(result.size()).isEqualTo(1);
    }

    @Test
    public void findByCategoryAndPriceBetween_singleCategoryWithSingleProductInDb_expectEmptyResult() {
        var category = createCategoryWithSingleProduct();
        testEntityManager.persist(category);
        var result = productDao.findByCategoryAndPriceBetween(category, 5.0, 6.0);
        assertThat(result.size()).isEqualTo(0);
    }

    @Test
    public void findProductByCategory_CategoryNameAndPriceBetween_singleCategoryWithSingleProductInDb_expectSingleProduct() {
        var category = createCategoryWithSingleProduct();
        testEntityManager.persist(category);
        var result = productDao.findProductByCategory_CategoryNameAndPriceBetween(category.getCategoryName(), 0.0, 2.0);
        assertThat(result.size()).isEqualTo(1);
    }

    private static Category createCategoryWithSingleProduct() {
        Product product = new Product();
        product.setPrice(1.00);

        Category category = new Category();
        category.setCategoryName("test");
        category.getProducts().add(product);
        product.setCategory(category);

        return category;
    }
}