Question

Brand

public class Brand implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "BrandID", nullable = false)
    private Integer brandID;
    @Basic(optional = false)
    @Column(name = "BrandName", nullable = false, length = 100)
    private String brandName;
    @Basic(optional = false)
    @Column(name = "Description", nullable = false, length = 1000)
    private String description;
    @Column(name = "Is_Visible")
    private Boolean isVisible;
    @JoinTable(name = "brandcategory", joinColumns = {
        @JoinColumn(name = "BrandID", referencedColumnName = "BrandID")}, inverseJoinColumns = {
        @JoinColumn(name = "CategoryID", referencedColumnName = "CategoryID")})
    @ManyToMany(fetch = FetchType.EAGER)
    private Collection<Category> categoryCollection;
    @OneToMany(mappedBy = "brand", fetch = FetchType.EAGER)
    private Collection<Product> productCollection;

I want to retrive the Brand IDs from table brandcategory whoes categoryID = :categoryID
how can i createnamed query for it in entity brand?

this does not work:

@NamedQuery(name = "Brand.getBrandListByCategory",
            query = "SELECT b FROM Brand b WHERE b.brandID =
            (SELECT bc.brandID
             FROM b.brandctegory bc
             WHERE bc.category.categoryID = :categoryID)")

Answer 1

If I understand correctly, you want all the brands belonging to a category. Why don’t you simply make the association bidirectional. You could then just do:

Category category = em.find(Category.class, categoryId);
return category.getBrands();

If it’s unidirectional, then you’ll need a query, but it’s much simpler that the one you tried:

select b from Brand b inner join b.categoryCollection category 
where category.id = :categoryId;

Your query doesn’t make sense: it uses a non-existing association (b.brandcategory). Remember that JPQL uses entities, their persistent fields and associations to other entities. And nothing else. Tables don’t exist in JPQL.