Caused by: java.lang.NullPointerException
   at org.hibernate.util.ConfigHelper.getResourceAsStream(ConfigHelper.java:144)
   at org.hibernate.cfg.Environment.<clinit>(Environment.java:515)

   public static InputStream getResourceAsStream(String resource) {
      String stripped = resource.startsWith("/") ?
            resource.substring(1) : resource;

      InputStream stream = null;
      ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
      if (classLoader!=null) {
         stream = classLoader.getResourceAsStream( stripped );
      }
      if ( stream == null ) {
         stream = Environment.class.getResourceAsStream( resource );
      }
      if ( stream == null ) {
         stream = Environment.class.getClassLoader().getResourceAsStream( stripped ); // THIS IS LINE 144
      }
      if ( stream == null ) {
         throw new HibernateException( resource + " not found" );
      }
      return stream;
   }

<beans>

   <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
      <property name="driverClassName" value="org.postgresql.Driver"/>
      <property name="url" value="jdbc3:postgresql://127.0.0.1:5432/oai"/>
      <property name="username" value="xxx"/>
      <property name="password" value="xxx"/>
   </bean>

    <bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean" lazy-init="false">
         <property name="dataSource" ref="dataSource"/>
     
         <property name="mappingResources">
           <list>
              <value>oai.hbm.xml</value>
           </list>
         </property>   
         <property name="hibernateProperties">
           <props>
            <prop key="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</prop>
         <prop key="hibernate.show_sql">true</prop>
         <prop key="hibernate.cglib.use_reflection_optimizer">true</prop>
         </props>   
         
         </property>
    </bean>
   
</beans>