java 使用Hibernate一对一Map时外键为空

sgtfey8w 于 2022-10-30 发布在 Java

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我正在尝试使用Hibernate，我有一个类问题和一个类答案，它们之间存在一对一的关系，代码运行成功，但外键为空，我不知道为什么。
第一个
我的hibernate.cfg.xml文件

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-configuration SYSTEM 
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
   <session-factory>

      <property name = "hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>

      <property name = "hibernate.connection.driver_class">com.mysql.jdbc.Driver </property>

      <!-- Assume test is the database name -->

      <property name = "hibernate.connection.url">jdbc:mysql://localhost:3306/aliens </property>

      <property name = "hibernate.connection.username">root</property>

      <property name = "hibernate.connection.password">root</property>
            <property name = "hibernate.hbm2ddl.auto">create</property>
        <property name = "show_sql">true</property>
      <!-- List of XML mapping files -->
                 <mapping  class= "io.com.learnHibernate.Question"/>
      <mapping  class= "io.com.learnHibernate.Answer"/>

   </session-factory>
</hibernate-configuration>

我的主要职责

package io.com.learnHibernate;

import org.hibernate.Session;
import org.hibernate.cfg.Configuration;
import org.hibernate.*;

import com.mysql.cj.xdevapi.SessionFactory;

/**
 * Hello world!
 *
 */
public class App 
{
    public static void main( String[] args )
    {
       //configuration
        Configuration conf=new Configuration();
        conf.configure("Hibernate.cfg.xml");
        org.hibernate.SessionFactory factory=conf.buildSessionFactory();

//creating answer 

        Answer a1=new Answer();
        a1.setaId(180);
        a1.setAnswer("my name is hafida");
        //creating question

        Question q1=new Question();
        q1.setQuestionId(3);
        q1.setQuestion("wht is your name?");
        q1.setAnswer(a1);

        //session 
        Session s=factory.openSession();
        Transaction tx=s.beginTransaction();

        //save
        s.save(q1);
          s.save(a1);

        tx.commit();
    //  s.close();
    //  factory.close();

    }
}

我希望插入外键的值，但它为空

Java

来源：https://stackoverflow.com/questions/74239065/foreign-key-is-null-while-using-hibernate-one-to-one-mapping

1条答案

按热度按时间

vof42yt11#

1.您需要在实体Map中指定级联类型：

@Entity
@Table(name="answer")
public class Answer {

    @Id
    private int aId;
    private String answer;

    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn
    private Question question;

    // ...
}

@Entity
@Table(name="question")
public class Question {

    @Id
    private int questionId;
    private String question;

    @OneToOne(mappedBy = "question", cascade = CascadeType.ALL)
    private Answer answer;

    // ...
}

1.当您使用双向@OneToOne时，您应该使两端同步：

Answer a1 = new Answer();
a1.setaId(180);
a1.setAnswer("my name is hafida");

Question q1 = new Question();
q1.setQuestionId(3);
q1.setQuestion("wht is your name?");

// make both sides in-sync
a1.setQuestion(q1);
q1.setAnswer(a1);

1.然后您可以使用以下方式保存它：

s.save(q1);

// you need not use s.save(a1);
// a1 will be saved due to propagation of the q1 entity's state

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java 使用Hibernate一对一Map时外键为空

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