java.lang.NullPointerException in a sample program of Hibernate

Question

i am try to run a sample application of hibernate, it give me a error on run time:

log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
Exception in thread "main" java.lang.NullPointerException at transaction.rollback();

this is in Main.java:

public class Main {

public static void main(String[] args) {
    Session session = HibernateUtil.getSessionFactory().openSession();
    Transaction transaction = null;
    try {
        transaction = session.beginTransaction();
        Address address = new Address("ABC", "Delhi", "TN", "110001");
        Student student = new Student("kumar", address);
        session.save(student);
        transaction.commit();
    } catch (HibernateException e) {
        transaction.rollback();
        e.printStackTrace();
    } finally {
        session.close();
    }

You can see from the exception output that it was thrown from the main method on a call to transaction.rollback() — Jon Freedman
– Jon Freedman, Commented Aug 16, 2010 at 12:56

Jon Freedman · Accepted Answer · 2010-08-16 12:28:33Z

1

Should change

transaction.rollback();

to

if (transaction != null) {
    transaction.rollback();
}

as its possible for the assignment of transaction to throw an exception.

If you want to get rid of the Log4J messages, you can add a call to

BasicConfigurator.configure();

to setup basic logging

answered Aug 16, 2010 at 12:28

Jon Freedman

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2 Comments

singh Over a year ago

where i should write this line: BasicConfigurator.configure();

Jon Freedman Over a year ago

Make it the first line in the main method, you can read more about log4j here - logging.apache.org/log4j/1.2/index.html but note, its been "superceeded" by logback logback.qos.ch

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