急！！在线等，hibernate运行问题,初学，求帮忙

出现以下异常
Exception in thread "main" org.hibernate.InvalidMappingException: Could not parse mapping document from resource cn/itcast/hibernate/User.hbm.xml
at org.hibernate.cfg.Configuration.addResource(Configuration.java:569)
at org.hibernate.cfg.Configuration.parseMappingElement(Configuration.java:1587)
at org.hibernate.cfg.Configuration.parseSessionFactory(Configuration.java:1555)
at org.hibernate.cfg.Configuration.doConfigure(Configuration.java:1534)
at org.hibernate.cfg.Configuration.doConfigure(Configuration.java:1508)
at org.hibernate.cfg.Configuration.configure(Configuration.java:1428)
at cn.itcast.hibernate.Base.main(Base.java:18)
Caused by: org.hibernate.MappingException: class it.itcast.hibernate.User not found while looking for property: id
at org.hibernate.util.ReflectHelper.reflectedPropertyClass(ReflectHelper.java:74)
at org.hibernate.mapping.SimpleValue.setTypeUsingReflection(SimpleValue.java:276)
at org.hibernate.cfg.HbmBinder.bindSimpleId(HbmBinder.java:401)
at org.hibernate.cfg.HbmBinder.bindRootPersistentClassCommonValues(HbmBinder.java:334)
at org.hibernate.cfg.HbmBinder.bindRootClass(HbmBinder.java:273)
at org.hibernate.cfg.HbmBinder.bindRoot(HbmBinder.java:144)
at org.hibernate.cfg.Configuration.add(Configuration.java:669)
at org.hibernate.cfg.Configuration.addInputStream(Configuration.java:504)
at org.hibernate.cfg.Configuration.addResource(Configuration.java:566)
... 6 more
Caused by: java.lang.ClassNotFoundException: it.itcast.hibernate.User
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at org.hibernate.util.ReflectHelper.classForName(ReflectHelper.java:100)
at org.hibernate.util.ReflectHelper.reflectedPropertyClass(ReflectHelper.java:70)
... 14 more

我的User类：

public class User {
private int id;
private String name;
private Date birthday;

public int getId() {
return id;
}
public void setId(int i) {
this.id = i;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}


}

User.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping
package="it.itcast.hibernate">

<class name="User">
<id name="id">
<generator class="native"/>
</id>
<property name="name" />
<property name="birthday" />
</class>

</hibernate-mapping>


hibernate.cfg.xml
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
<session-factory>
<property name="show_sql">true</property>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql:///mytest</property>
<property name="connection.username">root</property>
<property name="connection.password">123456</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hbm2ddl.auto">create-drop</property>




<mapping resource="cn/itcast/hibernate/User.hbm.xml"/>
</session-factory>
</hibernate-configuration>