Hibernate insert or select gives "Identifier of an instance altered"

[Brian Nice]

I'm new to Hibernate and just trying to get the quickstart up and running that is in the first chapter of the hibernate tutorial. I'm using Hibernate 3.0.5. When running the following code in my servlet:

 
        Session session = HibernateUtil.currentSession();
        Transaction tx = session.beginTransaction();
        Cat princess = new Cat();
        princess.setName(request.getParameter("name"));
        princess.setSex('F');
        princess.setWeight(7.4f);
        session.save(princess);
        tx.commit();
        HibernateUtil.closeSession();

I get the following error:

org.hibernate.HibernateException: identifier of an instance of org.hibernate.examples.quickstart.Cat altered from 1 to null

Here is the hibernate.cfg.xml and cat.hbm.xml:

  
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <property name="connection.datasource">java:comp/env/jdbc/quickstart</property>
    <property name="show_sql">true</property>
    <property name="dialect">org.hibernate.dialect.MySQLInnoDBDialect</property>
    <!-- Mapping files -->
    <mapping resource="Cat.hbm.xml"/>
  </session-factory>
</hibernate-configuration>
 
<?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>
  <class name="org.hibernate.examples.quickstart.Cat" table="CAT">
  <!-- A 32 hex character is our surrogate key. It's automatically generated by Hibernate with the UUID pattern. -->
    <id name="id" type="string" unsaved-value="null" >
      <column name="CAT_ID" sql-type="char(32)" not-null="true"/>
      <generator class="uuid.hex"/>
    </id>
  <!-- A cat has to have a name, but it shouldn' be too long. -->
    <property name="name">
      <column name="NAME" length="16" not-null="true"/>
    </property>
    <property name="sex"/>
    <property name="weight"/>
  </class>
</hibernate-mapping>

I am using MySQL database 4.1.12a with the MySql connector 3.1.10 on Windows XP. My script to create the table in Mysql is:

create table cat (
cat_id varchar(32) not null,
name varchar(16) not null,
sex char(1) not null,
weight float(2),
primary key (cat_id)
);

What is causing this error? Any help is greatly appreciated!
Thanks
Brian

[Jaikiran Pai]

Can you post the detail hibernate log

[Brian Nice]

The problem was in my persistent class, I had typed the set field incorrectly. Doh!

private Long id;
public void setId(Long Id) {
this.id = id;
}

Thanks
Brian