Question

我有一个实体UserFood，该实体包含另一个实体（食品和用户）的字段。当我仅使用JDBC时，我创建了此查询，以按用户ID和日期从“食物”搜索中选择总计：

"SELECT SUM(f.calories * uf.count) AS total_calories, ROUND(SUM(f.protein * uf.count),1) AS total_protein, ROUND(SUM(f.fat * uf.count),2) AS total_fat, ROUND(SUM(f.carbohydrate * uf.count),2) AS total_carbohydrate FROM users_food uf INNER JOIN food f ON uf.food_id = f.food_id WHERE uf.user_id = ? AND uf.date_added = ?;"

然后我可以将结果放入Map中，在其中我可以从表中将键设置为字段名称（total_calories，total_protein，total_fat，total_carbohydrate）

如何使用JPA（没有Hibernate和Spring）来做同样的事情？

我尝试至少从函数SUM中获取值，但出现错误。下面是我尝试做的事情：

public List findFoodFieldsTotalsByUserIdAndDate(Integer userId, LocalDate date) {
    EntityManagerFactory factory = Persistence.createEntityManagerFactory("mysql");
    EntityManager em = factory.createEntityManager();
    EntityTransaction transaction = em.getTransaction();
    transaction.begin();

    Query query = em.createQuery
            ("SELECT SUM(Food.calories * uf.count) AS total_calories, SUM(Food.protein * uf.count) AS total_protein, SUM(Food.fat * uf.count) AS total_fat, SUM(Food.carbohydrate * uf.count) AS total_carbohydrate FROM UserFood uf WHERE uf.user.id = :userId AND uf.dateAdded = :date");

    query.setParameter("userId", userId);
    query.setParameter("date", date);

    List resultList = query.getResultList();

    transaction.commit();
    em.close();
    factory.close();
    return resultList;
    }

我知道该错误恰好在查询中的某个地方，因为我创建了更简单的方法，并且一切正常：

public List<UserFood> findByUserIdAndDate(Integer userId, LocalDate date) {
    EntityManagerFactory factory = Persistence.createEntityManagerFactory("mysql");
    EntityManager em = factory.createEntityManager();
    EntityTransaction transaction = em.getTransaction();
    transaction.begin();

    TypedQuery<UserFood> query = em.createQuery
            ("SELECT uf FROM UserFood uf WHERE uf.user.id = :userId AND uf.dateAdded = :date", UserFood.class);
    query.setParameter("userId", userId);
    query.setParameter("date", date);
    List<UserFood> userFoodList = query.getResultList();

    transaction.commit();
    em.close();
    factory.close();
    return userFoodList;
}

在我的实体下面：

UserFood：

@EqualsAndHashCode
@NoArgsConstructor
@AllArgsConstructor
@Builder
@Getter
@Entity
@Table(name = "user_food")
public class UserFood {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "user_food_id")
private int id;

@ManyToOne
@JoinColumn(name = "user_fk_id")
private User user;

@OneToOne(cascade = CascadeType.PERSIST)
@JoinColumn(name = "food_fk_id")
private Food food;

private int count;

@Column(name = "date_added")
private LocalDate dateAdded;
}

用户：

@NoArgsConstructor
@AllArgsConstructor
@Builder
@Getter
@Setter
@Entity
public class User {
@Id
@GeneratedValue
@Column(name = "user_id")
private int id;

@Column(unique = true)
private String login;

@Column(length = 12)
private String password;

private LocalDate birthday;

private int height;

private int weight;

@Column(name = "norma_calories")
private int normaCalories;

@OneToOne(cascade = {CascadeType.PERSIST, CascadeType.REMOVE})
@JoinColumn(name = "activity_type_fk_id")
private ActivityType activityType;

@OneToOne(cascade = {CascadeType.PERSIST, CascadeType.REMOVE})
@JoinColumn(name = "role_fk_id")
private Role role;
}

食物：

@NoArgsConstructor
@AllArgsConstructor
@Builder
@Getter
@Entity
@NamedQueries({@NamedQuery(name = "findAllFood", query = "FROM Food f")})
public class Food {
@Id
@GeneratedValue
@Column(name = "food_id")
private int id;

private String name;

private int calories;

@Column(precision = 1)
private double protein;

@Column(precision = 1)
private double fat;

@Column(precision = 1)
private double carbohydrate;
}

如何使用JPA从函数SUM获取引用字段名称的值

0 个答案: