Hibernate version:2.1

Mapping documents: Iam using the following mapping <br><hibernate-mapping>
<class name="test.Item" table="item" >
<id name="id" column="id" type="java.lang.Integer" >
<generator class="sequence">
<param name="sequence">item_id_sequence</param>
</generator>
</id>

<property name="name" column="name" type="java.lang.String" />
<property name="description" column="description" type="java.lang.String" />
</class>
</hibernate-mapping>


Code between sessionFactory.openSession() and session.close():
Transaction tx = null;
Session session = ConnectionFactory.getInstance().getSession();

try
{
tx = session.beginTransaction();

Item item = new Item();
item.setDescription(addItemForm.getDescription());
item.setName(addItemForm.getName());

session.save(item);
tx.commit();
session.flush();
}
catch (HibernateException e)
{
System.err.println("Hibernate Exception" + e.getMessage());
throw new RuntimeException(e);
}



Full stack trace of any exception that occurs: org.apache.jasper.JasperException: net.sf.hibernate.MappingException: could not instantiate id generator
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1069)
org.apache.struts.tiles.TilesRequestProcessor.doForward(TilesRequestProcessor.java:274)
org.apache.struts.action.RequestProcessor.internalModuleRelativeForward(RequestProcessor.java:1012)
org.apache.struts.tiles.TilesRequestProcessor.internalModuleRelativeForward(TilesRequestProcessor.java:345)
org.apache.struts.action.RequestProcessor.processValidate(RequestProcessor.java:980)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:255)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:507)
javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

root cause

java.lang.RuntimeException: net.sf.hibernate.MappingException: could not instantiate id generator
test.ConnectionFactory.<init>(ConnectionFactory.java:69)
test.ConnectionFactory.getInstance(ConnectionFactory.java:103)
test.ItemService.getItemList(ItemService.java:204)
org.apache.jsp.jsp.test.AddItem_jsp._jspService(AddItem_jsp.java:120)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1069)
org.apache.struts.tiles.TilesRequestProcessor.doForward(TilesRequestProcessor.java:274)
org.apache.struts.action.RequestProcessor.internalModuleRelativeForward(RequestProcessor.java:1012)
org.apache.struts.tiles.TilesRequestProcessor.internalModuleRelativeForward(TilesRequestProcessor.java:345)
org.apache.struts.action.RequestProcessor.processValidate(RequestProcessor.java:980)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:255)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:507)
javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)


Name and version of the database you are using:postgresql 7.4

The generated SQL (show_sql=true):true

any help greatly appreciated
Thanks in advance

net.sf.hibernate.MappingException: could not instantiate id generator should show a nested exception.
try to majke it visible in your environment (no ex.getMessage())

The Mistake in the above problem was ,wrong entry in configuration ,i used
hibernate.dialect=net.sf.hibernate.dialect.HSQLDialect
instead of using
hibernate.dialect=net.sf.hibernate.dialect.PostgreSQLDialect
because my database in postgres