Null Pointer Exception @ SessionFactory

[Talha Kabakus]

Hello to everyone,

I'm new to Hibernate. I just want to do a sample project with Hibernate. But I've been taking exceptions, I'll be happy if someone can help me..
Thanks in advance..

  
	public Session openSession() {
		SessionFactory sessionFactory = new Configuration().configure("hibernate.cfg.xml").buildSessionFactory();
		return sessionFactory.openSession();
       }

       public void saveOrUpdate(Object o) {
		Session session = null;
		Transaction tx	 = null;
		try {
			session = openSession();
			tx = session.beginTransaction();
			session.saveOrUpdate(o);
			tx.commit();
		} catch(Exception e) {
			e.printStackTrace();
			tx.rollback();
		} finally {
			session.flush();
			session.close();
		}
	}
  

And here's my hibernate.cfg.xml file:

    
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">oracle.jdbc.OracleDriver</property>
        <property name="hibernate.connection.username">TALHA</property>
        <property name="hibernate.connection.password">00</property>
        <property name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:XE</property>
        <property name="hibernate.default_schema">TALHA</property>
        <property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property>
        <property name="show_sql">true</property>
        <property name="hibernate.connection.pool_size">10</property>
        <mapping class="model.Users" />
        
        <!-- Mapping files -->
        <mapping resource="Users.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

Full stacktrace:

    
java.lang.NullPointerException
	at dao.DAO.saveOrUpdate(DAO.java:30)
	at servlets.AddUser.doPost(AddUser.java:55)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:201)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:163)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:108)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:556)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:402)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:249)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:267)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:245)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:260)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
	at java.lang.Thread.run(Thread.java:636)

[Jeanne Boyarsky]

Talha,
The exception says it is being thrown in line 30 in saveOrUpdate. Which line is line 30? If I had to guess, I would imagine it is one of the lines in the catch or finally block. You should have a null check so you aren't trying to rollback the transaction if it is null. In other words, if Hibernate fails on creating a session, the code throws a Null Pointer in the catch block and you don't know what the original exception is. The finally block should have a similar null check for session.

[Talha Kabakus]

Thanks for your reply Jeanne..

Now I'm taking another exception :

org.hibernate.MappingException: An AnnotationConfiguration instance is required to use <mapping clazz="model.Users"/>

Here's my Users class that is generated Hibernate tools..