带有计数字段的 JPQL ManyToMany 查询

Question

我在具有 spring 安全性的 spring 引导应用程序中的两个实体（用户和电影）之间存在多对多关系。

我想创建一个 REST API 来查找所有电影并包含一个新字段，显示登录用户是否看过电影。

我找不到简单的方法，我只找到了在查询中创建新 DTO 对象的解决方案。接下来我展示我的代码。

实体如下：

电影：

@Entity
@Table(name = "movies")
public class Movies implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sequenceGenerator")
@SequenceGenerator(name = "sequenceGenerator")
private Long id;

@NotNull
@Size(max = 100)
@Column(name = "name", length = 100, nullable = false)
private String name;

@Column(name = "jhi_year")
private Long year;

@Size(max = 100)
@Column(name = "category", length = 100)
private String category;

@ManyToMany(mappedBy = "movies")
@JsonIgnore
@Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
private Set<User> users = new HashSet<>();

用户：

@Entity
@Table(name = "user")
public class User implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sequenceGenerator")
@SequenceGenerator(name = "sequenceGenerator")
private Long id;

@Size(max = 50)
@Column(name = "login", length = 50)
private String login;

@Size(max = 250)
@Column(name = "bio", length = 250)
private String bio;

@ManyToMany
@Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
@JoinTable(name = "user_movies",
           joinColumns = @JoinColumn(name="user_id", referencedColumnName="id"),
           inverseJoinColumns = @JoinColumn(name="movies_id", referencedColumnName="id"))

我所做的是一个 @Repository class 和一个像这样的 JPQL @query:

@Query("select new com.test.service.dto.MoviesDTO(movies.id, movies.name, movies.year, movies.category, " +
" count(users.id)) from Movies movies left join movies.users users on users.login = ?#{principal.username} group by movies.id ")
Page<MoviesDTO> findAll(Pageable pageable);

这很好用，但是有更简单的方法吗？最好找到一种方法来执行此操作，在实体 class 中添加一个新对象，避免在查询中创建一个新的 DTO 对象。

我知道这和我自己前段时间发的 this one 几乎是同一个问题，这对我来说仍然是个谜。

非常非常感谢！

Answer 1

感谢 jasarez 的回答。我为投影更改了 DOT，效果非常好！

存储库：

@Query("select movies.id as id, movies.name as name, movies.year as year, movies.category as category, count(users.id) as moviesCount " +
    "from Movies movies left join movies.users users on users.login = ?#{principal.username} group by movies.id")
     Page<MovieWithUserData> findAllWithUserData(Pageable pageable);

和投影：

public interface MovieWithUserData {

    Long getId();

    String getName();

    String getCategory();

    Integer getYear();

    Long getMoviesCount();

}

带有计数字段的 JPQL ManyToMany 查询

JPQL ManyToMany query with count field

java

jpa

spring-security

hibernate-mapping

spring-boot