Java Hibernate：非空属性引用空值或瞬态值

Hibernate : not-null property references a null or transient value

提问by Biboo Chung

Problem Solved. Thank you.

问题解决了。谢谢你。

Now I have three tables movie_information, release_companyand rating. movie_informationand ratingare having one-to-one relationship while release_companyand movie_informationare having one-to-many relationship. I am trying to build a CMS with hibernate but I found that I am not able to correctly construct the part that involve these three tables.

现在我有三张桌子movie_information，release_company和rating. movie_information并且rating正在建立一对一的关系，而release_company并且movie_information正在建立一对多的关系。我正在尝试使用 hibernate 构建一个 CMS，但我发现我无法正确构建涉及这三个表的部分。

Here comes my code

这是我的代码

MovieInformation.java

电影信息.java

public class MovieInformation {
    private ReleaseCompany releaseCompany;
    private Rating rating;
    // Other data member
    // Constructor, getter and setter
    public ReleaseCompany getReleaseCompany(){
        ReleaseCompany newReleaseCompany = new ReleaseCompany(this.releaseCompany);
        return newReleaseCompany;
    }
    public Rating getRating(){
        Rating newRating = new Rating(this.rating);
        return newRating;
    }
    public void setReleaseCompany(ReleaseCompany releaseCompany){
        this.releaseCompany = new ReleaseCompany(releaseCompany);
    }
}

ReleaseCompany.java

发布公司.java

public class ReleaseCompany {
    private int releaseCompanyId;
    private String releaseCompanyName;

    private Set<MovieInformation> movies = new HashSet<MovieInformation>();

    public ReleaseCompany(){
    }
    public ReleaseCompany(String releaseCompanyName){
        this.releaseCompanyName = releaseCompanyName;
    }
    public ReleaseCompany(ReleaseCompany releaseCompany){
        this.releaseCompanyName = releaseCompany.getReleaseCompanyName();
    }
    public Set<MovieInformation> getMovies() {  
        Set<MovieInformation> newMoviesSet = new HashSet<MovieInformation>(movies);
        return newMoviesSet;  
    }  
    public void setMovies(Set<MovieInformation> movies) {  
        this.movies = new HashSet<MovieInformation>(movies);
    }  
    // Other constructor, getter and setter
}

Rating.java

评级.java

public class Rating {
    private MovieInformation movie;
    // other data member

    public void setMovie(MovieInformation movie){
        this.movie = new MovieInformation(movie);
    }
    // other constructor, getter and setter
}

---

---

MovieInformation.hbm.xml

电影信息.hbm.xml

<class name="cart.hibernate.movieInformation.MovieInformation" table="movie_information">
    <id column="move_id" name="movieId" type="long">
        <generator class="native"/>
    </id>

    <one-to-one name="rating" class="cart.hibernate.rating.Rating" cascade="save-update"></one-to-one> 

    <many-to-one name="releaseCompany" class="cart.hibernate.releaseCompany.ReleaseCompany"  unique="false"><!-- constrained="true" -->
        <column name="release_company_id" not-null="true" />
    </many-to-one>
    // Other property
</class>

Rating.hbm.xml

评级.hbm.xml

<class name="cart.hibernate.rating.Rating" table="rating">
  <id name="movieId" type="java.lang.Long">
      <column name="movie_id" />
      <generator class="foreign">
          <param name="property">movie</param>
      </generator>
  </id>

  <property column="avg_rate" name="avgRate" type="double"/>
  <property column="num_of_rate" name="numOfRate" type="long"/>

  <one-to-one name="movie" class="cart.hibernate.movieInformation.MovieInformation" constrained="true"></one-to-one>
</class>

ReleaseCompany.hbm.xml

发布公司.hbm.xml

<class name="cart.hibernate.releaseCompany.ReleaseCompany" table="release_company">
    <id column="release_company_id" name="releaseCompanyId" type="int">
        <generator class="native"/>
    </id>
    <property column="release_company_name" name="releaseCompanyName" type="string"/>

    <set name="movies" table="movie_information" inverse="true" lazy="true" fetch="select">
        <key>
            <column name="movie_id" not-null="true" />
        </key>
        <one-to-many class="cart.hibernate.movieInformation.MovieInformation" />
    </set>
</class>

Testing Main method

测试主要方法

Session session = HibernateUtil.getSessionFactory().openSession();
Transaction tx = null;
tx = session.beginTransaction();

Rating rating = new Rating(5.6, 80);
ReleaseCompany releaseCompany = new ReleaseCompany();
releaseCompany.setReleaseCompanyName("a");
session.save(releaseCompany);        

//  ReleaseCompany releaseCompany = (ReleaseCompany)session.get(ReleaseCompany.class, 15); 
//  Another testing case that I have tried. It throw another exception,
//  if you need the information in this part, please let me know.

MovieInformation movie = new MovieInformation("Matrix", 150, 1, 50, date, releaseDate, "good description");
movie.setRating(rating);
movie.setReleaseCompany(releaseCompany);

rating.setMovie(movie);

session.save(movie);  // <--- Error occur here
tx.commit();

StackTrace

堆栈跟踪

org.hibernate.PropertyValueException: not-null property references a null or transient value: cart.hibernate.movieInformation.MovieInformation.releaseCompany
    at org.hibernate.engine.Nullability.checkNullability(Nullability.java:100)
    at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:312)
    at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:203)
    at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:129)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
    at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
    at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
    at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:713)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:701)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:697)
    at cart.hibernate.movieInformation.ManageMovieInformation.main(ManageMovieInformation.java:61)
BUILD SUCCESSFUL (total time: 1 second)

I have read several similar question, some of the people said the releaseCompany(in my case) object hasn't saved to the database so the setReleaseCompany()cannot work as expected. I am not sure whether the releaseCompanyobject exist or not because I cannot see the record in MySql(I am not sure whether the record would be saved or not if exceptions are thrown). Moreover, some of them said the attribute of the mapping tag is not correct but I am not sure whether mine are correct or not.

我读过几个类似的问题，有些人说releaseCompany（在我的情况下）对象没有保存到数据库中，因此setReleaseCompany()无法按预期工作。我不确定releaseCompany对象是否存在，因为我看不到 MySql 中的记录（如果抛出异常，我不确定是否会保存记录）。此外，他们中的一些人说映射标签的属性不正确，但我不确定我的是否正确。

I apologies to put so much code in the post, hope that you could solve this problem.

很抱歉在帖子里放了这么多代码，希望你能解决这个问题。

回答by ben75

Keep it simple :

把事情简单化 ：

public class MovieInformation {
    private ReleaseCompany releaseCompany;
    private Rating rating;
    // Other data member
    // Constructor, getter and setter
    public ReleaseCompany getReleaseCompany(){
        return releaseCompany;
    }
    public Rating getRating(){
        return rating;
    }
    public void setReleaseCompany(ReleaseCompany releaseCompany){
        this.releaseCompany = releaseCompany;
    }
}

---

---

public class ReleaseCompany {
    private int releaseCompanyId;
    private String releaseCompanyName;

    private Set<MovieInformation> movies = new HashSet<MovieInformation>();

    public ReleaseCompany(){
    }
    public ReleaseCompany(String releaseCompanyName){
        this.releaseCompanyName = releaseCompanyName;
    }

    public ReleaseCompany(ReleaseCompany releaseCompany){
        this.releaseCompanyName = releaseCompany.getReleaseCompanyName();
    }
    public Set<MovieInformation> getMovies() {  
        return movies;  
    }  
    private void setMovies(Set<MovieInformation> movies) {  
        this.movies = movies;
    }  
    // Other constructor, getter and setter
}

---

---

public class Rating {
    private MovieInformation movie;
    // other data member

    public void setMovie(MovieInformation movie){
        this.movie = movie;
    }
    // other constructor, getter and setter
}

Please note that setMovies(Set movies)is private, so the only way to change all movies is to do something like this:

请注意，这setMovies(Set movies)是私有的，因此更改所有电影的唯一方法是执行以下操作：

releaseCompany.getMovies().clear();
releaseCompany.getMovies().addAll(newMovieCollection);

You need to that because:

你需要这样做，因为：

• hibernate need to track the changes made to the collection
• hibernate put a proxy around the collection to do this tracking.
• replacing the Setby another one implies that the hibernate proxy will be lost

• hibernate 需要跟踪对集合所做的更改
• hibernate 在集合周围放置一个代理来执行此跟踪。
• 用Set另一个替换意味着休眠代理将丢失