Hibernate异常org.hibernate.PropertyValueException：非空属性引用null或瞬态值

你好，我目前正在开发小应用程序来练习休眠。我试图做一对多的关系，我被卡住了。Hibernate异常org.hibernate.PropertyValueException：非空属性引用null或瞬态值

我有2类问题与答案：

package com.sample; 

import java.util.List; 

public class Question { 
    private int id; 
    private String qname; 
    private List<Answer> answers; 

    public Question() { 

    } 

    public Question(int id, String qname, List<Answer> answers) { 
     super(); 
     this.id = id; 
     this.qname = qname; 
     this.answers = answers; 
    } 

    public int getId() { 
     return id; 
    } 

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

    public String getQname() { 
     return qname; 
    } 

    public void setQname(String qname) { 
     this.qname = qname; 
    } 

    public List<Answer> getAnswers() { 
     return answers; 
    } 

    public void setAnswers(List<Answer> answers) { 
     this.answers = answers; 
    } 

}

和

package com.sample; 

public class Answer { 
    private int id; 
    private String answername; 
    private String postedBy; 
    private Question question; 

    public Answer() { 

    } 

    public Answer(int id, String answername, String postedBy, Question question) { 
     super(); 
     this.id = id; 
     this.answername = answername; 
     this.postedBy = postedBy; 
     this.question = question; 
    } 

    public int getId() { 
     return id; 
    } 

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

    public String getAnswername() { 
     return answername; 
    } 

    public void setAnswername(String answername) { 
     this.answername = answername; 
    } 

    public String getPostedBy() { 
     return postedBy; 
    } 

    public void setPostedBy(String postedBy) { 
     this.postedBy = postedBy; 
    } 

    public Question getQuestion() { 
     return question; 
    } 

    public void setQuestion(Question question) { 
     this.question = question; 
    } 


}

的配置文件如下：

question.hbm.xml：

<?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="com.sample.Question" table="question"> 
     <id name="id"> 
      <generator class="increment"></generator> 
     </id> 
     <property name="qname"></property> 

     <bag name="answers" table="answer" inverse="true" lazy="true" 
      fetch="select" cascade="all"> 
      <key> 
       <column name="question_id" not-null="true"> 
       </column> 
      </key> 
      <one-to-many class="com.sample.Answer"></one-to-many> 
     </bag> 

    </class> 

</hibernate-mapping>

answer.h bm.xml：

<?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="com.sample.Answer" table="answer"> 
     <id name="id"> 
      <generator class="increment"></generator> 
     </id> 
     <property name="answername"></property> 
     <property name="postedBy"></property> 
     <many-to-one name="question" class="com.sample.Question" 
      fetch="select"> 
      <column name="question_id" not-null="true"> 
      </column> 
     </many-to-one> 
    </class> 

</hibernate-mapping>

我的主要文件是这样的：

import java.util.ArrayList; 

import org.hibernate.*; 
import org.hibernate.cfg.*; 

public class StoreData { 
    public static void main(String[] args) { 
     Session session = SessionFactoryUtil.getSessionFactory() 
       .getCurrentSession(); 
     Transaction t = session.beginTransaction(); 

     Answer ans1 = new Answer(); 
     ans1.setAnswername("java is a programming language"); 
     ans1.setPostedBy("Ravi Malik"); 

     Answer ans2 = new Answer(); 
     ans2.setAnswername("java is a platform"); 
     ans2.setPostedBy("Sudhir Kumar"); 

     Answer ans3 = new Answer(); 
     ans3.setAnswername("Servlet is an Interface"); 
     ans3.setPostedBy("Jai Kumar"); 

     Answer ans4 = new Answer(); 
     ans4.setAnswername("Servlet is an API"); 
     ans4.setPostedBy("Arun"); 

     ArrayList<Answer> list1 = new ArrayList<Answer>(); 
     list1.add(ans1); 
     list1.add(ans2); 

     ArrayList<Answer> list2 = new ArrayList<Answer>(); 
     list2.add(ans3); 
     list2.add(ans4); 

     Question question1 = new Question(); 
     question1.setQname("What is Java?"); 
     question1.setAnswers(list1); 

     Question question2 = new Question(); 
     question2.setQname("What is Servlet?"); 
     question2.setAnswers(list2); 

     session.persist(question1); 
     session.persist(question2); 

     t.commit(); 
//  session.close(); 
     System.out.println("success"); 

    } 
}

当我运行应用程序，我得到以下错误：

Exception in thread "main" org.hibernate.PropertyValueException: not-null property references a null or transient value : com.sample.Answer.question 
    at org.hibernate.engine.internal.Nullability.checkNullability(Nullability.java:106) 
    at org.hibernate.action.internal.AbstractEntityInsertAction.nullifyTransientReferencesIfNotAlready(AbstractEntityInsertAction.java:132) 
    at org.hibernate.action.internal.AbstractEntityInsertAction.makeEntityManaged(AbstractEntityInsertAction.java:141) 
    at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:203) 
    at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:181) 
    at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:168) 
    at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:332) 
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:288) 
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:194) 
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:137) 
    at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:206) 
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:149) 
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:801) 
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:794) 
    at org.hibernate.engine.spi.CascadingActions$7.cascade(CascadingActions.java:314) 
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:350) 
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:293) 
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:161) 
    at org.hibernate.engine.internal.Cascade.cascadeCollectionElements(Cascade.java:379) 
    at org.hibernate.engine.internal.Cascade.cascadeCollection(Cascade.java:319) 
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:296) 
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:161) 
    at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:118) 
    at org.hibernate.event.internal.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:460) 
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:294) 
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:194) 
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:137) 
    at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:206) 
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:149) 
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:75) 
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:811) 
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:784) 
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
    at java.lang.reflect.Method.invoke(Unknown Source) 
    at org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:356) 
    at com.sun.proxy.$Proxy0.persist(Unknown Source) 
    at com.sample.StoreData.main(StoreData.java:46)

来源

2015-03-13 user1286254

我相信你的问题ID没有生成。当您试图将问题保存在数据库中时，您的问题ID仍为空。当您尝试将null分配给类的原始数据成员时，会发生此错误。 – muasif80 2015-03-13 13:22:13

我通过首先添加问题，然后将问题设置为答案来修复它。

Question question1 = new Question(); 
    question1.setQname("What is Java?"); 

    Question question2 = new Question(); 
    question2.setQname("What is Servlet?"); 

    session.persist(question1); 
    session.persist(question2); 

    Answer ans1 = new Answer(); 
    ans1.setAnswername("java is a programming language"); 
    ans1.setPostedBy("Ravi Malik"); 
    ans1.setQuestion(question1); 

    Answer ans2 = new Answer(); 
    ans2.setAnswername("java is a platform"); 
    ans2.setPostedBy("Sudhir Kumar"); 
    ans2.setQuestion(question1); 

    Answer ans3 = new Answer(); 
    ans3.setAnswername("Servlet is an Interface"); 
    ans3.setPostedBy("Jai Kumar"); 
    ans3.setQuestion(question2); 

    Answer ans4 = new Answer(); 
    ans4.setAnswername("Servlet is an API"); 
    ans4.setPostedBy("Arun"); 
    ans4.setQuestion(question2); 

    session.persist(ans1); 
    session.persist(ans2); 
    session.persist(ans3); 
    session.persist(ans4);

来源

2015-03-17 09:21:30 user1286254

Hibernate试图保存答案，有参考在保存时没有身份证的问题。

尝试先保存没有答案的问题，然后为每个答案调用setQuestion传递保存的问题。并保存答案。

来源

2015-03-13 13:32:31 StanislavL

Hibernate异常org.hibernate.PropertyValueException：非空属性引用null或瞬态值

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