conn.prepareStatement failed

[cosmos38240]

Hi,

I try to execute this tutorial :
http://www.tusc.com.au/tutorial/html/chap3.html

when i execute this code :

conn = jdbcFactory.getConnection();
 String queryString = "select userid from storeaccess where username=? and password=?";
 ps = conn.prepareStatement(queryString);
 ps.setString(1, username);

I go to error on conn.prepareStatement

how could i know the reason ???

Thank you

[cosmos38240]

this my log :

Caused by: java.lang.NullPointerException
 at au.com.tusc.dao.StoreAccessDAOImpl.loginUser(StoreAccessDAOImpl.java:70)
 at au.com.tusc.session.StoreAccessSession.loginUser(StoreAccessSession.java:61)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:324)
 at org.jboss.invocation.Invocation.performCall(Invocation.java:345)
 at org.jboss.ejb.StatelessSessionContainer$ContainerInterceptor.invoke(StatelessSessionContainer.java:214)
 at org.jboss.resource.connectionmanager.CachedConnectionInterceptor.invoke(CachedConnectionInterceptor.java:185)
 at org.jboss.ejb.plugins.StatelessSessionInstanceInterceptor.invoke(StatelessSessionInstanceInterceptor.java:113)
 at org.jboss.webservice.server.ServiceEndpointInterceptor.invoke(ServiceEndpointInterceptor.java:51)
 at org.jboss.ejb.plugins.CallValidationInterceptor.invoke(CallValidationInterceptor.java:48)
 at org.jboss.ejb.plugins.AbstractTxInterceptor.invokeNext(AbstractTxInterceptor.java:105)
 at org.jboss.ejb.plugins.TxInterceptorCMT.runWithTransactions(TxInterceptorCMT.java:316)
 at org.jboss.ejb.plugins.TxInterceptorCMT.invoke(TxInterceptorCMT.java:149)
 at org.jboss.ejb.plugins.SecurityInterceptor.invoke(SecurityInterceptor.java:128)
 at org.jboss.ejb.plugins.LogInterceptor.invoke(LogInterceptor.java:191)
 ... 25 more