Weird Exception

[Siddharth Bhargava]

Hi Friends,
I am facing a weird exception while running a simple program in Hibernate.

Following is the code snippet.

public static void main(String[] args) {
		// TODO Auto-generated method stub
		Session session = null;

		try {
			System.out.println("Before Session Factory !!!");
			SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
			System.out.println("After Session Factory !!! ");
			
			session = sessionFactory.openSession();

			System.out.println("Inserting Record");

			Transaction tx = session.beginTransaction();

			Contact contact = new Contact();
			//contact.setId(4);
			contact.setFirstName("Sid");
			contact.setLastName("B");
			contact.setEmail("[e-mail]");
						
			Address address = new Address();
			address.setAddress1("My Sweeet Home");
			address.setAddress2("Line No. 2");
			address.setCity("ABC City");
			address.setZipcode(11);
			
			contact.setHomeAddress(address);
			
			session.save(contact);
			
			tx.commit();

			System.out.println("Done");

		} catch (Exception e) {
			System.out.println(e.getMessage());
		} finally {
			session.flush();
			session.close();
		}

	}

hibernarte.cfg.xml

<hibernate-configuration>

	<session-factory>
		
		<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
	    <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernategenerators</property>  
      	<property name="hibernate.connection.username">root</property>
      	<property name="hibernate.connection.password">root</property>
      	<property name="hibernate.connection.pool_size">10</property>
      	
      	
      	<property name="show_sql">true</property>
      	<property name="format_sql">true</property>

      	
      	<!-- Show and print nice SQL on stdout. -->
       	
      	<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
      	<property name="hibernate.hbm2ddl.auto">create</property>
      	
      	<!-- List of XML Mapping files -->
<!--   	<mapping resource="contact.hbm.xml"/> -->
      	<mapping resource="contact1.hbm.xml"/>
<!--   	<mapping resource="address.hbm.xml"/> -->
	
	</session-factory>
	
</hibernate-configuration>

When I run this program in eclipse I get the following exception.

Before Session Factory !!!
Exception in thread "main" java.lang.NullPointerException
	at com.example.hibernategenerators.SaveExample.main(SaveExample.java:51)

It shows NullPointer at session.flush

It seems that the session factory is not getting created properly.

What is the problem with the code. Why is sessionfactory not getting created properly. Please help !!!

Thanks and Regards,
Sid.

[Paul Sturrock]

If the SessionFactory fails in its configuration step you will be able to see why in the stack trace Hibernate will produce. What else does your log say?

[Siddharth Bhargava]

Hi Paul,
My log only says this in the Eclipse console :

Before Session Factory !!!
Exception in thread "main" java.lang.NullPointerException
	at com.example.hibernategenerators.SaveExample.main(SaveExample.java:51)

Thanks and Regards,
Sid.

[Paul Sturrock]

Hibernate reports errors if there are any in its configuration, however you can write code that poorly displays these errors. Why not print the stack trace rather than the message? This code:

} catch (Exception e) {  
            System.out.println(e.getMessage());  
        }

only works when an exception contains a message.

[Siddharth Bhargava]

Hi Paul,
I wrote the line for printing stack trace - e.printStacktrace() - but to no avail. Its still showing the following line in the console.

Before Session Factory !!!
Exception in thread "main" java.lang.NullPointerException
	at com.example.hibernategenerators.SaveExample.main(SaveExample.java:51)

Thanks and Regards,
Sid.

[Waswani Naresh]

Hi Sid,

Nothing is wrong with your configuration and/or the main code.

The issue is --> you do not have few jars in your class path that are internally referred by Hibernate framework and because of which when you try to execute the program, you get a java.lang.NoClassDefFoundError and because you have a catch() block looking for Exceptions, it is not able to catch this error.

Replace Exception with Throwable in catch() block and you will come to know which class/classes are missing.


Regards,
Naresh Waswani

[Siddharth Bhargava]

Hi Naresh,
Thanks for your post. It worked. Should I have both catch(Throwable e) and catch(Exception e) so that I know about classes which are missing as well as the exceptions ? Can we do this as a good practice ?

Thanks and Regards,
Sid.

[Waswani Naresh]

Hi Sid,

Since Throwable is the parent class of Exception, it can catch any type of exceptions or errors. Generally its a good practice to have generic Exception at the end but if you think there could be some error sort of scenarios, Exception can be replaced with Throwable class.

Regards,
Naresh Waswani

[Siddharth Bhargava]

Hi Waswani,
Would keep your suggestions in mind. Thanks a ton again !!!.


Thanks and Regards,
Sid.