java - hibernate 错误: "java.lang.Integer cannot be cast to java.lang.String" and so on

Question

我遇到过这样的情况:一部电影可以有很多评论，但评论只与一部电影相关。我遇到了如下所述的问题，但由于我现在已经尝试了很多排列，所以我实际上有点困惑，所以在我再搞乱我的代码之前，我认为最好在这里问一下。

问:应该如何设置？在保存评论之前，我可以在评论中将 movie_id 硬设置为 int 吗？或者我是否需要有一个 MovieDTO 电影对象作为 ReviewDTO 类中的对象之一？当我创建要保存的评论对象时，我调用 review.setMovie(someMovieObject)？

所以这是我的代码中发生的错误:

1. 首先它提示未设置非空电影引用(Hibernate:非空属性引用空值或 transient 值)，因此在无法修复它之后，有人建议删除约束，看看它是否有效。

2. 现在它提示“java.lang.Integer 无法转换为 java.lang.String”，但我很困惑哪里存在类型不匹配？类<->Hibernate还是Hibernate<->DB？

很困惑，有人可以解释一下吗...？提前致谢。

package edu.unsw.comp9321.jdbc;

public class ReviewDTO {
    private int id; 
    private String review; 
    private String rating; 
    private int client_id;
    private int movie_id;

    public ReviewDTO() {
    }

    public ReviewDTO(int id, String review, String rating, int client_id, int movie_id) {
        super();
        this.id = id;
        this.review = review;
        this.rating = rating;
        this.client_id = client_id;
        this.movie_id = movie_id;
    }

    public int getid() {
        return id;
    }
    public void setid(int id) {
        this.id = id;
    }

    public String getReview() {
        return review;
    }
    public void setReview(String review) {
        this.review = review;
    }

    public String getRating() {
        return rating;
    }
    public void setRating(String rating) {
        this.rating = rating;
    }

    public int getClient_id() {
        return client_id;
    }
    public void setClient_id(String client_id) {
        this.client_id = new Integer(client_id);
    }   

    public int getMovie_id() {
        return movie_id;
    }
    public void setMovie_id(int movie_id) {
        this.movie_id = movie_id;
    }
}


package edu.unsw.comp9321.jdbc;

import java.util.Comparator;
import java.util.HashSet;
import java.util.Set;

import javax.persistence.OneToMany;


public class MovieDTO implements Comparable {
    private int id;
    private String title;
    private String poster;
    private String director;
    private String actors;
    private String synopsis;
    private String release_date;
    private int cinema_id;
    private Set<GenreDTO> genres = new HashSet<GenreDTO>();
    private Set<ReviewDTO> reviews = new HashSet<ReviewDTO>();
    private double rating;

    public MovieDTO() {
    }

    public MovieDTO(int id, String title, String poster, String director,
            String actors, String synopsis, String release_date, double rating) {
        super();
        this.id = id;
        this.title = title;
        this.poster = poster;
        this.director = director;
        this.actors = actors;
        this.synopsis = synopsis;
        this.release_date = release_date;
        this.rating = rating;
    }

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }

    public String getPoster() {
        return poster;
    }
    public void setPoster(String poster) {
        this.poster = poster;
    }

    public String getDirector() {
        return director;
    }
    public void setDirector(String director) {
        this.director = director;
    }

    public String getActors() {
        return actors;
    }
    public void setActors(String actors) {
        this.actors = actors;
    }

    public String getSynopsis() {
        return synopsis;
    }
    public void setSynopsis(String synopsis) {
        this.synopsis = synopsis;
    }

    public String getRelease_date() {
        return release_date;
    }
    public void setRelease_date(String release_date) {
        this.release_date = release_date;
    }

    public Set<GenreDTO> getGenres() {
        return genres;
    }
    public void setGenres(Set<GenreDTO> genres) {
        this.genres = genres;
    }

    public Set<ReviewDTO> getReviews() {
        return reviews;
    }
    public void setReviews(Set<ReviewDTO> reviews) {
        this.reviews = reviews;
    }

    public int getCinema_id() {
        return cinema_id;
    }
    public void setCinema_id(int cinema_id) {
        this.cinema_id = cinema_id;
    }

    public double getRating() {
        return rating;
    }
    public void setRating(double rating) {
        this.rating = rating;
    }

    @Override
    public int compareTo(Object o) {
        MovieDTO other = (MovieDTO) o;
        if (this.rating > other.rating) return -1;
        if (this.rating < other.rating) return 1;
        return 0;
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
  <class name="edu.unsw.comp9321.jdbc.ReviewDTO" table="Review" >
        <id column="id" name="id">
            <generator class="identity" />
        </id>
        <property column="review" name="review" type="string" />
        <property column="rating" name="rating" type="string" />
        <property column="client_id" name="client_id" type="string" />
        <property column="movie_id" name="movie_id" type="string" />
    </class>
</hibernate-mapping>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
  <class name="edu.unsw.comp9321.jdbc.MovieDTO" table="Movie" >
        <id column="id" name="id">
            <generator class="identity" />
        </id>
        <property column="title" name="title" type="string" />
        <property column="poster" name="poster" type="string" />
        <property column="director" name="director" type="string" />
        <property column="actors" name="actors" type="string" />
        <property column="synopsis" name="synopsis" type="string" />
        <property column="release_date" name="release_date" type="string" />
        <set name="genres" table="MovieHasGenre" >
            <key column="movie_id" not-null="true" />
            <many-to-many class="edu.unsw.comp9321.jdbc.GenreDTO" column="genre_id" />
        </set>
        <set name="reviews" table="Review" >
            <key column="movie_id" />
            <one-to-many class="edu.unsw.comp9321.jdbc.ReviewDTO" />
        </set>
    </class>
</hibernate-mapping>

Answer 1

您收到的第一个错误是因为您定义了 <key column="movie_id" not-null="true" />这意味着movie_id GenreDTO 内不能为 null其中MovieDTO 。在代码中的某个位置，当尝试持久化时，该值为空(没有显示足够的代码来告诉您位置。)

第二个错误是因为你定义了<property column="movie_id" name="movie_id" type="string" />但在你的ReviewDTO movie_id是一个整数。它们应该是相同的。

至于你的问题，是否应该使用movie_id或MovieDTO在你的ReviewDTO 。这取决于几件事。双向关系很好(意味着 ReviewDTO 附加了 MovieDTO ，而相同的 MovieDTO 在 ReviewDTO 列表中具有相同的 Reviews 。但是，如果您相反，只留下 movie_id 整数意味着任何时候您想要来自 MovieDTO 的 ReviewDTO 对象，您将有另一个数据库调用...但是这可能不会太昂贵，因为如果它是双向的方向性，无论如何，该调用都会发生。