コレクション間でエンティティを結合

import com.mongodb.hibernate.annotations.ObjectIdGenerator;import org.bson.types.ObjectId;import java.time.Instant;import java.util.List;import jakarta.persistence.Embedded;
import jakarta.persistence.Entity;import jakarta.persistence.FetchType;import jakarta.persistence.Id;import jakarta.persistence.OneToMany;import jakarta.persistence.Table;
@Entity@Table(name = "movies")public class Movie {   @Id   @ObjectIdGenerator   private ObjectId id;   private String title;   private String plot;   private int year;   private List<String> cast;   private List<String> directors;   private Instant released;   @Embedded   private Awards awards;   @OneToMany(mappedBy = "movie", fetch = FetchType.LAZY)   private List<Comment> comments;
   public Movie(String title, String plot, int year, List<String> cast, List<String> directors, Instant released, Awards awards) {      this.title = title;      this.plot = plot;      this.year = year;      this.cast = cast;      this.directors = directors;      this.released = released;      this.awards = awards;   }
   public Movie() {
   }
   public ObjectId getId() {      return id;   }
   public String getTitle() {      return title;   }
   public void setTitle(String title) {      this.title = title;   }
   public String getPlot() {      return plot;   }
   public void setPlot(String plot) {      this.plot = plot;   }
   public int getYear() {      return year;   }
   public void setYear(int year) {      this.year = year;   }
   public List<String> getCast() {      return cast;   }
   public void setCast(List<String> cast) {      this.cast = cast;   }
   public List<String> getDirectors() {      return directors;   }
   public void setDirectors(List<String> directors) {      this.directors = directors;   }
   public Awards getAwards() {      return awards;   }
   public void setAwards(Awards awards) {      this.awards = awards;   }
   public Instant getReleased() {      return released;   }
   public void setReleased(Instant released) {      this.released = released;   }
   public List<Comment> getComments() {      return comments;   }
   public void setComments(List<Comment> comments) {      this.comments = comments;   }}

package org.example;
import com.mongodb.hibernate.annotations.ObjectIdGenerator;import jakarta.persistence.Column;import org.bson.types.ObjectId;import java.time.Instant;
import jakarta.persistence.Entity;import jakarta.persistence.FetchType;import jakarta.persistence.Id;import jakarta.persistence.JoinColumn;import jakarta.persistence.ManyToOne;import jakarta.persistence.Table;
@Entity@Table(name = "comments")public class Comment {    @Id    @ObjectIdGenerator    @Column(name = "_id")    private ObjectId id;    private String name;    private String email;    private String text;    private Instant date;
    @ManyToOne(fetch = FetchType.LAZY)    @JoinColumn(name = "movie_id")    private Movie movie;
    public Comment(String name, String email, String text, Instant date, Movie movie) {        this.name = name;        this.email = email;        this.text = text;        this.date = date;        this.movie = movie;    }
    public Comment() {
    }
    public ObjectId getId() {        return id;    }
    public void setId(ObjectId id) {        this.id = id;    }
    public String getName() {        return name;    }
    public void setName(String name) {        this.name = name;    }
    public String getEmail() {        return email;    }
    public void setEmail(String email) {        this.email = email;    }
    public String getText() {        return text;    }
    public void setText(String text) {        this.text = text;    }
    public Instant getDate() {        return date;    }
    public void setDate(Instant date) {        this.date = date;    }
    public Movie getMovie() {        return movie;    }
    public void setMovie(Movie movie) {        this.movie = movie;    }
}

package org.example;
import com.mongodb.hibernate.annotations.ObjectIdGenerator;import jakarta.persistence.Column;import org.bson.types.ObjectId;
import jakarta.persistence.Entity;import jakarta.persistence.Id;import jakarta.persistence.Table;
@Entity@Table(name = "users")public class User {    @Id    @ObjectIdGenerator    @Column(name = "_id")    private ObjectId id;    private String name;    private String email;
    public User(String name, String email) {        this.name = name;        this.email = email;    }
    public User() {
    }
    public ObjectId getId() {        return id;    }
    public void setId(ObjectId id) {        this.id = id;    }
    public String getName() {        return name;    }
    public void setName(String name) {        this.name = name;    }
    public String getEmail() {        return email;    }
    public void setEmail(String email) {        this.email = email;    }
}

{  "_id": { "bookNo": 7, "publisherId": 30 },  "comment": "An excellent read.",  "book": { "bookNo": 2, "publisherId": 10 }}

{  "$lookup": {    "from": "books",    "let": {      "v0_r1_0_book_publisherId": "$book.publisherId",      "v1_r1_0_book_bookNo": "$book.bookNo"    },    "pipeline": [      {        "$match": {          "$expr": {            "$and": [              { "$eq": [ "$_id.publisherId", "$$v0_r1_0_book_publisherId" ] },              { "$eq": [ "$_id.bookNo", "$$v1_r1_0_book_bookNo" ] }            ]          }        }      }    ],    "as": "#b1_0"  }},{ "$unwind": "$#b1_0" }

{  "$lookup": {    "from": "reviews",    "let": {      "v0_b1_0__id_publisherId": "$_id.publisherId",      "v1_b1_0__id_bookNo": "$_id.bookNo"    },    "pipeline": [      {        "$match": {          "$expr": {            "$and": [              { "$eq": [ "$$v0_b1_0__id_publisherId", "$_id.publisherId" ] },              { "$eq": [ "$$v1_b1_0__id_bookNo", "$_id.bookNo" ] }            ]          }        }      }    ],    "as": "#r1_0"  }},{ "$unwind": "$#r1_0" }