Hibernate中one-to-many的例子，出问题了（请进，贴出了错误和源程序）

Question

package many;
public class Publication {
private String id;
private String bookName = null;
private String stateDate = null;
private Author author = null;
/**
 * Method setId
 *
 *
 * @param id
 *
 */
public void setId(String id) {
// TODO: Add your code here
this.id = id;
} /**
 * Method getId
 *
 *
 * @return
 *
 */
public String getId() {
// TODO: Add your code here
return this.id;
} /**
 * Method getBookName
 *
 *
 * @return
 *
 */
public String getBookName() {
// TODO: Add your code here
return this.bookName;
} /**
 * Method setBookName
 *
 *
 * @param bookName
 *
 */
public void setBookName(String bookName) {
// TODO: Add your code here
this.bookName = bookName;
} /**
 * Method setDate
 *
 *
 * @param date
 *
 */
public void setStateDate(String stateDate) {
// TODO: Add your code here
this.stateDate = stateDate;
} /**
 * Method getDate
 *
 *
 * @return
 *
 */
public String getStateDate() {
// TODO: Add your code here
return this.stateDate;
}
public void setAuthor( Author author )
{
this.author = author;
}
public Author getAuthor()
{
return this.author;
}
}

Answer 1

package many;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;import net.sf.hibernate.HibernateException;
import net.sf.hibernate.MappingException;
import net.sf.hibernate.Session;
import net.sf.hibernate.SessionFactory;
import net.sf.hibernate.Transaction;
import net.sf.hibernate.cfg.Configuration;
import net.sf.hibernate.tool.hbm2ddl.SchemaExport;public class Example{
    
    private static SessionFactory _sessions = null;
    private static Properties pops = new Properties();
    
    static{
        try {
            
            Configuration cfg = new Configuration();
            
            cfg.addClass(Author.class);
            cfg.addClass(Publication.class);
            SchemaExport dbExport = new SchemaExport(cfg);
            dbExport.create(true, true);
            _sessions = cfg.buildSessionFactory();
            
        } catch (MappingException e) {
           e.printStackTrace();
        } catch (HibernateException e) {
           e.printStackTrace();
        }
    
    }
    
    public static void main(String[] args) throws HibernateException {
        
        
        Publication publication1 = new Publication();
        publication1.setId("00001");
        publication1.setBookName("AAA");
        publication1.setStateDate("20031224");
        Publication publication2 = new Publication();
        publication2.setId("00002");
        publication2.setBookName("BBB");
        publication2.setStateDate("20031225");
        
        Author author = new Author(); author.setId("Z0001");
        author.setName("smallduzi");
        author.getPublications().add(publication1);
        author.getPublications().add(publication2);
        
        //publication1.setAuthor(author);
        //publication2.setAuthor(author);        Session session = _sessions.openSession();
        
        Transaction tx = null;
        try{
            tx = session.beginTransaction();
            session.save(author);
            session.flush();
            tx.commit();
           
            System.out.println("over");
        }catch(HibernateException he){
            if(tx != null) tx.rollback();
            throw he;
        }
        finally{
            session.close();
        }
        
    }
    
}

Answer 2

<?xml version="1.0" encoding="GB2312"?>
<!DOCTYPE hibernate-mapping SYSTEM "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >
<hibernate-mapping>
    <class name="many.Author" table="author" dynamic-update="true" dynamic-insert="true"> 
        <id name="id" column="id">
<!--uuid.hex-->
            <generator class="assigned"/>
        </id>
        <property name="name" column="Name" />
        <set name="publications" lazy="false" inverse="true" cascade="all">
          <key column="author_id"/> 
          <one-to-many class="many.Publication" />
        </set>
    </class>
</hibernate-mapping>

Answer 3

<?xml version="1.0" encoding="GB2312"?>
<!DOCTYPE hibernate-mapping SYSTEM "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >
<hibernate-mapping>
    <class name="many.Publication" table="Publication" dynamic-update="true" dynamic-insert="true"> 
        <id name="id" column="Id">
<!--
            <generator class="sequence">
<param name="sequence">Reader_Id_Seq</param>
            </generator>
-->
 <generator class="assigned"/>
        </id>
        <property name="bookName" column="BookName" />
        <property name="stateDate" column="stateDate" />
        <many-to-one name="author" cascade="all" outer-join="auto" update="true" insert="true" column="author_id" />
    </class>
</hibernate-mapping>

Answer 4

输出以及错误信息如下：在这里为什么是
update Publication set BookName=?, stateDate=?, author_id=? where Id=?而不是insert呢？问题就可能在这里。请帮忙看看。create table Publication (
   Id VARCHAR2(255) not null,
   BookName VARCHAR2(255),
   stateDate VARCHAR2(255),
   author_id VARCHAR2(255),
   primary key (Id)
)
create table author (
   id VARCHAR2(255) not null,
   Name VARCHAR2(255),
   primary key (id)
)
alter table Publication add constraint FK23254A0C57F3E04F foreign key (author_id) references author
Hibernate: insert into author (Name, id) values (?, ?)
Hibernate: update Publication set BookName=?, stateDate=?, author_id=? where Id=?
Exception in thread "main" net.sf.hibernate.HibernateException: SQL update or deletion failed (row not found)
        at net.sf.hibernate.impl.NonBatchingBatcher.addToBatch(NonBatchingBatcher.java:25)
        at net.sf.hibernate.persister.EntityPersister.update(EntityPersister.java:642)
        at net.sf.hibernate.persister.EntityPersister.update(EntityPersister.java:611)
        at net.sf.hibernate.impl.ScheduledUpdate.execute(ScheduledUpdate.java:31)
        at net.sf.hibernate.impl.SessionImpl.executeAll(SessionImpl.java:2100)
        at net.sf.hibernate.impl.SessionImpl.execute(SessionImpl.java:2062)
        at net.sf.hibernate.impl.SessionImpl.flush(SessionImpl.java:2005)
        at many.Example.main(Example.java:66)

Answer 5

inverse="true" 把它去了试试看!

Answer 6

hbm.xml id 属性加上unsaved-value="0"

Answer 7

1.你的Publication(child)的主键是assigned
2.你的Author(parent)的inverse=false,cascade="all"表明由parent控制关联,并且级联save,update,delete child.
3.save parent时,hibernate发现parent拥有的child的主键都不为空,认为children都是已持久化的po,于是调用update 的sql更新所有的child状态.
4.你的数据库中没有存储期待被更新的po的数据,发生异常.