hibernate中的异常（一对一）

Question

我遵循一个基本的Hibernate教程。我试图在两个表之间建立一对一的关系。当我尝试插入Client表时，它可以工作，但是当我尝试执行相反的操作（插入Facture表）时，我得到了这个异常：

INFO: HHH000227: Running hbm2ddl schema export
Hibernate: alter table facture drop foreign key FK_i4kuo9pjcqstd2tpftv9eprbk
oct. 20, 2014 3:15:05 PM org.hibernate.tool.hbm2ddl.SchemaExport perform
ERROR: HHH000389: Unsuccessful: alter table facture drop foreign key FK_i4kuo9pjcqstd2tpftv9eprbk
oct. 20, 2014 3:15:05 PM org.hibernate.tool.hbm2ddl.SchemaExport perform
ERROR: Table 'mybase.facture' doesn't exist
Hibernate: drop table if exists client
Hibernate: drop table if exists facture
Hibernate: create table client (client_id integer not null auto_increment, Nom varchar(255), primary key (client_id))
Hibernate: create table facture (num_fact integer not null auto_increment, client_id integer, primary key (num_fact))
Hibernate: alter table facture add constraint FK_i4kuo9pjcqstd2tpftv9eprbk foreign key (client_id) references client (client_id)
oct. 20, 2014 3:15:05 PM org.hibernate.tool.hbm2ddl.SchemaExport execute
INFO: HHH000230: Schema export complete
Hibernate: insert into facture (client_id) values (?)
oct. 20, 2014 3:15:05 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 1452, SQLState: 23000
oct. 20, 2014 3:15:05 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: Cannot add or update a child row: a foreign key constraint fails (`mybase`.`facture`, CONSTRAINT `FK_i4kuo9pjcqstd2tpftv9eprbk` FOREIGN KEY (`client_id`) REFERENCES `client` (`client_id`))
Exception in thread "main" org.hibernate.exception.ConstraintViolationException: could not execute statement
    at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:72)
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:211)
    at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:96)
    at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:58)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3032)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3558)
    at org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:98)
    at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:490)
    at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:195)
    at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:179)
    at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:214)
    at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:324)
    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:125)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:209)
    at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:55)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:194)
    at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:49)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
    at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:715)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:707)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:702)
    at com.zack.hibernate.Main.main(Main.java:28)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`mybase`.`facture`, CONSTRAINT `FK_i4kuo9pjcqstd2tpftv9eprbk` FOREIGN KEY (`client_id`) REFERENCES `client` (`client_id`))
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)

这是客户端类：

   @Entity
@Table (name="client")
public class Client implements java.io.Serializable {

    @Id /* pour dire a hibernate que id est une cle primaire*/
    @GeneratedValue /* pour que hibernate générer automatiquement la clé primaire*/

    private int client_id;

    @Column(name="Nom")/* pour forcer hibernate a nommer la colonne par "Nom"*/
    private String nom;

    @OneToOne (mappedBy = "c")
    private Facture f;

这是制作类：

    @Entity
@Table(name="facture")
public class Facture implements java.io.Serializable {
    @Id
    @GeneratedValue
    private int num_fact;

    @OneToOne
    @JoinColumn(name = "client_id")
    private Client c;

这是Main类：

    public class Main {
  public class Main {

    public static void main(String[] args) {
        Client c = new Client();
        c.setClient_id(1);
        c.setNom("Zack Smith");


        Facture f = new Facture();
        f.setNum_fact(1);       
        //c une étape importante
        c.setF(f);

        f.setC(c);



        SessionFactory s = new AnnotationConfiguration().configure().buildSessionFactory();
        Session ss = s.openSession();
        ss.beginTransaction();

        ss.save(f);

        ss.getTransaction().commit();
        ss.close();
        s.close();

    }
}

数据库图片：http://hpics.li/f1a3ee7

Answer 1

public class Main {

    public static void main(String[] args) {

        Client c = new Client();
        c.setId(1);;
        c.setNom("Zack");


        Facture f = new Facture();
        f.setNum_fact(1);
        f.setC(c);
        c.setF(f);


//        Facture f = new Facture();
//        f.setNum_fact(1);       
//        //c une étape importante
//        c.setF(f);
//
//        f.setC(c);



        SessionFactory s = new AnnotationConfiguration().configure().buildSessionFactory();
        Session ss = s.openSession();
        ss.beginTransaction();
        ss.save(c);
        ss.save(f);

        ss.getTransaction().commit();
        ss.close();
        s.close();


    }

}

===============================================================================================

oct. 22, 2014 6:50:34 PM org.hibernate.tool.hbm2ddl.SchemaExport execute
INFO: HHH000227: Running hbm2ddl schema export
Hibernate: alter table Facture drop foreign key FK_rqdue6x5d4b9lg97rxve2fq20
oct. 22, 2014 6:50:34 PM org.hibernate.tool.hbm2ddl.SchemaExport perform
ERROR: HHH000389: Unsuccessful: alter table Facture drop foreign key FK_rqdue6x5d4b9lg97rxve2fq20
oct. 22, 2014 6:50:34 PM org.hibernate.tool.hbm2ddl.SchemaExport perform
ERROR: Table 'mybase.facture' doesn't exist
Hibernate: drop table if exists Client
Hibernate: drop table if exists Facture
Hibernate: create table Client (id integer not null auto_increment, nom varchar(255), primary key (id))
Hibernate: create table Facture (num_fact integer not null auto_increment, client_id integer, primary key (num_fact))
Hibernate: alter table Facture add constraint FK_rqdue6x5d4b9lg97rxve2fq20 foreign key (client_id) references Client (id)
oct. 22, 2014 6:50:34 PM org.hibernate.tool.hbm2ddl.SchemaExport execute
INFO: HHH000230: Schema export complete
Hibernate: insert into Client (nom) values (?)
Hibernate: insert into Facture (client_id) values (?)
oct. 22, 2014 6:50:34 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
INFO: HHH000030: Cleaning up connection pool [jdbc:mysql://localhost:3306/mybase]

谢谢你们的帮助，它的工作：）

Answer 2

在我看来，您可能对Hibernate如何建立这些关系有点困惑。我认为您的异常是由于您说您的clientId列/字段是映射到Facture表的生成值，而您实际上希望它将Client表上的clientId列/字段作为外键引用。因此，您正试图保存制作对象，这将导致制作。要生成的clientId列（因为您使用@GenericGenerator对其进行了注释）。由于设置了此值，Hibernate尝试使用生成的ID更新现有的客户端对象。由于该对象实际上不存在，因此您会收到您发布的异常。

您尝试做的基本上是允许Hibernate映射外键关系，以便您可以从Facture获取Client，反之亦然。

您不需要指定联接列，Hibernate默认为所有关系的@Id列。您应该修改客户端类，如下所示

@Entity
@Table (name="client")
public class Client implements java.io.Serializable {

    @Id 
    @GeneratedValue 
    private int clientId;

    //Keep the nom field, I just removed it for brevity.

    @OneToOne (cascade = CascadeType.ALL)
    private Facture facture;

并修改您的制作类，如下所示：

@Entity
@Table(name="facture")
public class Facture implements java.io.Serializable {

    @Id 
    @GeneratedValue
    private int factureId;

    @OneToOne (cascade = CascadeType.ALL)
    private Client client;

假设您的数据库设置正确，当您在其中任何一个对象上调用save时，这就是Hibernate正确保存对象所需的全部内容。

试试这个，如果你不能让它工作，让我知道。