Odd NullPointerException

[subhashchandra medhiassam]

Dear friends,
I have run into a problem and need your help in solving it.

I am trying to map the values of the fields of an object into a relational database table.

The file hibernate.cfg.xml looks like the following :

    
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
<session-factory>
      <property name="hibernate.connection.driver_class">

com.mysql.jdbc.Driver</property>
      <property name="hibernate.connection.url">

jdbc:mysql://localhost/hibernatetutorial</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="dialect">org.hibernate.dialect.MySQLDialect</property>
      <property name="hibernate.hbm2ddl.auto">update</property>
      <!-- Mapping files -->
      <mapping resource="contactdetails.hbm.xml"/>
</session-factory>
</hibernate-configuration>

The POJO class named ContactDetails.java looks like the following :

 
package firstHibernateExample;

public class ContactDetails {
	
	  private String firstName;
	  private String lastName;
	  private String email;
	  private long id;

	  /**
	   * @return Email
	   */
	  public String getEmail() {
	    return email;
	  }

	  /**
	   * @return First Name
	   */
	  public String getFirstName() {
	    return firstName;
	  }

	  /** 
	   * @return Last name
	   */
	  public String getLastName() {
	    return lastName;
	  }

	  /**
	   * @param string Sets the Email
	   */
	  public void setEmail(String string) {
	    email = string;
	  }

	  /**
	   * @param string Sets the First Name
	   */
	  public void setFirstName(String string) {
	    firstName = string;
	  }

	  /**
	   * @param string sets the Last Name
	   */
	  public void setLastName(String string) {
	    lastName = string;
	  }

	  /**
	   * @return ID Returns ID
	   */
	  public long getId() {
	    return id;
	  }

	  /**
	   * @param l Sets the ID
	   */
	  public void setId(long l) {
	    id = l;
	  }


}  

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
  <class name="firstHibernateExample.ContactDetails" table="CONTACTDETAILS">
   <id name="id" type="long" column="ID" >
   <generator class="assigned"/>
  </id>

  <property name="firstName">
     <column name="FIRSTNAME" />
  </property>
  <property name="lastName">
    <column name="LASTNAME"/>
  </property>
  <property name="email">
    <column name="EMAIL"/>
  </property>
 </class>
</hibernate-mapping>

And the class used to set the values into the POJO is named as FirstExample.java. It looks like the following:

    
package firstHibernateExample;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class FirstExample {
	
	  public static void main(String[] args) {
	    Session session = null;

	    try{
	      //This step will read hibernate.cfg.xml and prepare hibernate for use
	      SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
	      session =sessionFactory.openSession();
	      Transaction tx = session.beginTransaction();   
	      
	      //Create new instance of Contact and set values in it by reading them from form object
	      System.out.println("Inserting Record");
	      ContactDetails contact = new ContactDetails();
	      contact.setId((long)3);
	      contact.setFirstName("Subhash");
	      contact.setLastName("Medhi");
	      contact.setEmail("[e-mail]");
	      session.save(contact);
	      tx.commit();
	      System.out.println("Done");
	     
	    }catch(Exception e){
	      System.out.println(e.getMessage());
	    }finally {
	      // Actual contact insertion will happen at this step
	      session.flush();
	      session.close();
	    }
	    
	  
	 }

}

But when i execute FirstExample.java, i am getting a NulPointerException corresponding to the statement session.flush(); which is in the finally block.
What should i do now ? Kindly help me out.


Subhash

[Paul Sturrock]

So most likely your session is not created in the first place. Have a look at your logs, there should be another error message in there.

[subhashchandra medhiassam]

Hi,
I have sorted out the problem. I had not included some of the jars. Thanks for the help anyway.

Subhash

[Lei Guoguo]

subhashchandra medhiassam wrote:Dear friends,

    
package firstHibernateExample;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class FirstExample {
	
	  public static void main(String[] args) {
	    Session session = null;

	    try{
	      //This step will read hibernate.cfg.xml and prepare hibernate for use
	      SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
	      session =sessionFactory.openSession();
	      Transaction tx = session.beginTransaction();   
	      
	      //Create new instance of Contact and set values in it by reading them from form object
	      System.out.println("Inserting Record");
	      ContactDetails contact = new ContactDetails();
	      contact.setId((long)3);
	      contact.setFirstName("Subhash");
	      contact.setLastName("Medhi");
	      contact.setEmail("[e-mail]");
	      session.save(contact);
	      tx.commit();
	      System.out.println("Done");
	     
	    }catch(Exception e){
	      System.out.println(e.getMessage());
	    }finally {
	      // Actual contact insertion will happen at this step
	      session.flush();
	      session.close();
	    }
	    
	  
	 }

}

But when i execute FirstExample.java, i am getting a NulPointerException corresponding to the statement session.flush(); which is in the finally block.
What should i do now ? Kindly help me out.


Subhash

you can try in this way:

......
finally {
if(session != null) {
session.flush();
session.close();
session = null;
}
}