hibernate 插入数据失败

[xiaozhimin1978]

数据库：MySql
数据表：
CREATE TABLE `mystudent` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(20) default NULL,
`address` varchar(100) NOT NULL default '',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=gbk ROW_FORMAT=REDUNDANT;

mystudent.hbm.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping SYSTEM "hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="per.dao.MyStudent" table="mystudent">
		<id name="id" column="id" type="java.lang.Long">
			<generator class="identity" />
		</id>
		<property name="name" type="string" column="name"/>
		<property name="address" type="string" column="address" />
	</class>
</hibernate-mapping>

bean:

package per.dao;

public class MyStudent{
	private Long id;
	public Long getId(){
		return id;
	}
	public void setId(Long value){
		this.id = id;
	}
	
	private String name = "";
	public String getName(){
		return name;
	}
	public void setName(String value){
		name = value;
	}
	
	private String address = "";
	public String getAddress(){
		return address;
	}
	public void setAddress(String value){
		address = value;
	}
}

测试的java代码：

import org.hibernate.*;
import org.hibernate.cfg.*;
import per.dao.*;

class HibernateUtil {

    public static final SessionFactory sessionFactory;

    static {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static final ThreadLocal<Session> session = new ThreadLocal<Session>();

    public static Session currentSession() throws HibernateException {
        Session s = session.get();
        // Open a new Session, if this thread has none yet
        if (s == null) {
            s = sessionFactory.openSession();
            // Store it in the ThreadLocal variable
            session.set(s);
        }
        return s;
    }
	
    public static void closeSession() throws HibernateException {
        Session s = (Session) session.get();
        if (s != null)
            s.close();
        session.set(null);
    }
}

public class TestHibernate{
	public static void main(String[] args){
		Session session = HibernateUtil.currentSession();
		Transaction trans = session.beginTransaction();
		
		MyStudent stu = new MyStudent();
		stu.setName("张三");
		stu.setAddress("湖南");
		
		session.save(stu);
		
		trans.commit();
		HibernateUtil.closeSession();
	}
}

运行时出现如下错误，我看了错误是在 Transaction.commit()中，很奇怪啊：
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment
).
log4j:WARN Please initialize the log4j system properly.
Exception in thread "main" org.hibernate.HibernateException: identifier of an in
stance of per.dao.MyStudent was altered from 8 to null
at org.hibernate.event.def.DefaultFlushEntityEventListener.checkId(Defau
ltFlushEntityEventListener.java:51)
at org.hibernate.event.def.DefaultFlushEntityEventListener.getValues(Def
aultFlushEntityEventListener.java:140)
at org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity
(DefaultFlushEntityEventListener.java:97)
at org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(A
bstractFlushingEventListener.java:195)
at org.hibernate.event.def.AbstractFlushingEventListener.flushEverything
ToExecutions(AbstractFlushingEventListener.java:76)
at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlus
hEventListener.java:26)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:908)
at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:344)
at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java
:106)
at TestHibernate.main(TestHibernate.java:52)

[Shine_Panda]

id,还有实体类 用 Integer 类型映射试下看。

[jdlsfl]

[Quote=引用 1 楼 caoyinghui1986 的回复:]
id,还有实体类 用 Integer 类型映射试下看。
[/Quote]

[老廉颇尚能饭否]

<property name="name" type="[color=#FF0000]string

" column="name"/>
<property name="address" type="string" column="address" />[/color]
配置文件的问题吧：
identifier of an in
stance of per.dao.MyStudent was altered
你再检查检查。

[xiaozhimin1978]

我已经找到原因了

MyStudent.setId(Long value) 方法错误

应该是 this.id = value;