one to one mapping problem

[Samanthi perera]

here is my exam class

package my;

import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.Table;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.AnnotationConfiguration;

@Entity
@Table(name = "exam", schema = "school")
public class Exam implements Serializable {

    private int id;
    private String shortName;
    private ExamDetail detail;

    @Id
    @GeneratedValue
    @Column(name = "id")
    public int getId() {
        return id;
    }

    private void setId(int id) {
        this.id = id;
    }

    @Basic
    public String getShortName() {
        return shortName;
    }

    public void setShortName(String shortName) {
        this.shortName = shortName;
    }

    /* Notice that the Exam maintains an
    instance of the ExamDetail class. */
    @OneToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name ="detail_id")
    public ExamDetail getDetail() {
        return detail;
    }

    public void setDetail(ExamDetail detail) {
        this.detail = detail;
    }

    public static void main(String args[]) {
        // Session session = HibernateUtil.getSessionFactory().openSession();
        AnnotationConfiguration config = new AnnotationConfiguration();
        config.addAnnotatedClass(Exam.class);
        config.addAnnotatedClass(ExamDetail.class);
        SessionFactory sessionFack = config.configure().buildSessionFactory();
        //SessionFactory sessionFack = new AnnotationConfiguration().configure().buildSessionFactory();
        Session session = sessionFack.openSession();
        Transaction transaction = null;
        try {
            Exam exam = new Exam();
            exam.setShortName("SCJA");

            ExamDetail detail = new ExamDetail();
            detail.setFullName("Sun Certified Java Associate");
            detail.setPassingPercentage(62);
            detail.setNumberOfQuestions(55);
            exam.setDetail(detail);


            session.save(exam);
             session.save(detail);
            System.out.println("user saved");
            transaction.commit();
            System.out.println("transaction successful!!!");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

here is me examDetail class

package my;

import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name = "exam_detail", schema = "school")
public class ExamDetail implements Serializable {

    private int id;
    private String fullName;
    private int numberOfQuestions;
    private int passingPercentage;
    private Exam exam;

    @Id
    @GeneratedValue
    @Column(name = "id")
    public int getId() {
        return id;
    }

    @OneToOne(cascade = CascadeType.ALL, mappedBy = "detail")
    public Exam getExam() {
        return exam;
    }

    public void setExam(Exam exam) {
        this.exam = exam;
    }

    private void setId(int id) {
        this.id = id;
    }

     @Basic
    public String getFullName() {
        return fullName;
    }

    public void setFullName(String fullName) {
        this.fullName = fullName;
    }

     @Basic
    public int getNumberOfQuestions() {
        return numberOfQuestions;
    }

    public void setNumberOfQuestions(int numberOfQuestions) {
        this.numberOfQuestions = numberOfQuestions;
    }

    @Basic
    public int getPassingPercentage() {
        return passingPercentage;
    }

    public void setPassingPercentage(int passingPercentage) {
        this.passingPercentage = passingPercentage;
    }
}

here is error i am getting

init:
deps-module-jar:
deps-ear-jar:
deps-jar:
compile-single:
run-main:
Mar 17, 2010 8:06:54 AM org.hibernate.cfg.annotations.Version <clinit>
INFO: Hibernate Annotations 3.3.1.GA
Mar 17, 2010 8:06:54 AM org.hibernate.cfg.Environment <clinit>
INFO: Hibernate 3.2.5
Mar 17, 2010 8:06:54 AM org.hibernate.cfg.Environment <clinit>
INFO: hibernate.properties not found
Mar 17, 2010 8:06:54 AM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: Bytecode provider name : cglib
Mar 17, 2010 8:06:54 AM org.hibernate.cfg.Environment <clinit>
INFO: using JDK 1.4 java.sql.Timestamp handling
Mar 17, 2010 8:06:54 AM org.hibernate.cfg.Configuration configure
INFO: configuring from resource: /hibernate.cfg.xml
Mar 17, 2010 8:06:54 AM org.hibernate.cfg.Configuration getConfigurationInputStream
INFO: Configuration resource: /hibernate.cfg.xml
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.Configuration doConfigure
INFO: Configured SessionFactory: null
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.AnnotationBinder bindClass
INFO: Binding entity from annotated class: my.Exam
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.annotations.EntityBinder bindTable
INFO: Bind entity my.Exam on table exam
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.AnnotationBinder bindClass
INFO: Binding entity from annotated class: my.ExamDetail
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.annotations.EntityBinder bindTable
INFO: Bind entity my.ExamDetail on table exam_detail
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.AnnotationBinder bindClass
INFO: Binding entity from annotated class: my.User
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.annotations.EntityBinder bindTable
INFO: Bind entity my.User on table user
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.AnnotationConfiguration secondPassCompile
INFO: Hibernate Validator not found: ignoring
Mar 17, 2010 8:06:55 AM org.hibernate.connection.DriverManagerConnectionProvider configure
INFO: Using Hibernate built-in connection pool (not for production use!)
Mar 17, 2010 8:06:55 AM org.hibernate.connection.DriverManagerConnectionProvider configure
INFO: Hibernate connection pool size: 20
Mar 17, 2010 8:06:55 AM org.hibernate.connection.DriverManagerConnectionProvider configure
INFO: autocommit mode: false
Mar 17, 2010 8:06:55 AM org.hibernate.connection.DriverManagerConnectionProvider configure
INFO: using driver: com.mysql.jdbc.Driver at URL: jdbc:mysql://localhost:3306/school
Mar 17, 2010 8:06:55 AM org.hibernate.connection.DriverManagerConnectionProvider configure
INFO: connection properties: {user=root, password=****}
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: RDBMS: MySQL, version: 5.1.43-community
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: JDBC driver: MySQL-AB JDBC Driver, version: mysql-connector-java-5.1.6 ( Revision: ${svn.Revision} )
Mar 17, 2010 8:06:55 AM org.hibernate.dialect.Dialect <init>
INFO: Using dialect: org.hibernate.dialect.MySQLDialect
Mar 17, 2010 8:06:55 AM org.hibernate.transaction.TransactionFactoryFactory buildTransactionFactory
INFO: Using default transaction strategy (direct JDBC transactions)
Mar 17, 2010 8:06:55 AM org.hibernate.transaction.TransactionManagerLookupFactory getTransactionManagerLookup
INFO: No TransactionManagerLookup configured (in JTA environment, use of read-write or transactional second-level cache is not recommended)
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Automatic flush during beforeCompletion(): disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Automatic session close at end of transaction: disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: JDBC batch size: 15
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: JDBC batch updates for versioned data: disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Scrollable result sets: enabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: JDBC3 getGeneratedKeys(): enabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Connection release mode: auto
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Maximum outer join fetch depth: 2
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Default batch fetch size: 1
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Generate SQL with comments: disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Order SQL updates by primary key: disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Order SQL inserts for batching: disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory createQueryTranslatorFactory
INFO: Query translator: org.hibernate.hql.ast.ASTQueryTranslatorFactory
Mar 17, 2010 8:06:55 AM org.hibernate.hql.ast.ASTQueryTranslatorFactory <init>
INFO: Using ASTQueryTranslatorFactory
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Query language substitutions: {}
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: JPA-QL strict compliance: disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Second-level cache: enabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Query cache: disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory createCacheProvider
INFO: Cache provider: org.hibernate.cache.NoCacheProvider
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Optimize cache for minimal puts: disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Structured second-level cache entries: disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Echoing all SQL to stdout
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Statistics: disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Deleted entity synthetic identifier rollback: disabled
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
Hibernate: insert into school.exam_detail (fullName, numberOfQuestions, passingPercentage) values (?, ?, ?)
INFO: Default entity-mode: pojo
Hibernate: insert into school.exam (detail_id, shortName) values (?, ?)
user saved
Mar 17, 2010 8:06:55 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Named query checking : enabled
Mar 17, 2010 8:06:55 AM org.hibernate.impl.SessionFactoryImpl <init>
INFO: building session factory
Mar 17, 2010 8:06:56 AM org.hibernate.impl.SessionFactoryObjectFactory addInstance
INFO: Not binding factory to JNDI, no JNDI name configured
java.lang.NullPointerException
        at my.Exam.main(Exam.java:82)
BUILD SUCCESSFUL (total time: 2 seconds)

[Cameron Wallace McKenzie]

The error is happening at this line:

transaction.commit();

It might even appear that it is a problem getting the actual connection. I see a JNDI lookup there. Perhaps either the connection pool is not being obtained by the JNDI lookup, or if you've configured transactions through JNDI, the JNDI lookup on the UserTransaction object is failing.

For some reason your transaction is not committing. That's the key. Do you have any idea why that line of code might be failing?

[Samanthi perera]

I put session.save(detail); above the session.save(exam);.

now it seems llike this

            session.save(detail);
            session.save(exam);
            System.out.println("user saved");
            transaction.commit();
            System.out.println("transaction successful!!!");

then it gives this error

init:
deps-module-jar:
deps-ear-jar:
deps-jar:
compile-single:
run-main:
Mar 17, 2010 8:31:22 AM org.hibernate.cfg.annotations.Version <clinit>
INFO: Hibernate Annotations 3.3.1.GA
Mar 17, 2010 8:31:22 AM org.hibernate.cfg.Environment <clinit>
INFO: Hibernate 3.2.5
Mar 17, 2010 8:31:22 AM org.hibernate.cfg.Environment <clinit>
INFO: hibernate.properties not found
Mar 17, 2010 8:31:22 AM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: Bytecode provider name : cglib
Mar 17, 2010 8:31:22 AM org.hibernate.cfg.Environment <clinit>
INFO: using JDK 1.4 java.sql.Timestamp handling
Mar 17, 2010 8:31:22 AM org.hibernate.cfg.Configuration configure
INFO: configuring from resource: /hibernate.cfg.xml
Mar 17, 2010 8:31:22 AM org.hibernate.cfg.Configuration getConfigurationInputStream
INFO: Configuration resource: /hibernate.cfg.xml
Mar 17, 2010 8:31:22 AM org.hibernate.cfg.Configuration doConfigure
INFO: Configured SessionFactory: null
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.AnnotationBinder bindClass
INFO: Binding entity from annotated class: my.Exam
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.annotations.EntityBinder bindTable
INFO: Bind entity my.Exam on table exam
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.AnnotationBinder bindClass
INFO: Binding entity from annotated class: my.ExamDetail
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.annotations.EntityBinder bindTable
INFO: Bind entity my.ExamDetail on table exam_detail
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.AnnotationBinder bindClass
INFO: Binding entity from annotated class: my.User
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.annotations.EntityBinder bindTable
INFO: Bind entity my.User on table user
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.AnnotationConfiguration secondPassCompile
INFO: Hibernate Validator not found: ignoring
Mar 17, 2010 8:31:23 AM org.hibernate.connection.DriverManagerConnectionProvider configure
INFO: Using Hibernate built-in connection pool (not for production use!)
Mar 17, 2010 8:31:23 AM org.hibernate.connection.DriverManagerConnectionProvider configure
INFO: Hibernate connection pool size: 20
Mar 17, 2010 8:31:23 AM org.hibernate.connection.DriverManagerConnectionProvider configure
INFO: autocommit mode: false
Mar 17, 2010 8:31:23 AM org.hibernate.connection.DriverManagerConnectionProvider configure
INFO: using driver: com.mysql.jdbc.Driver at URL: jdbc:mysql://localhost:3306/school
Mar 17, 2010 8:31:23 AM org.hibernate.connection.DriverManagerConnectionProvider configure
INFO: connection properties: {user=root, password=****}
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: RDBMS: MySQL, version: 5.1.43-community
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: JDBC driver: MySQL-AB JDBC Driver, version: mysql-connector-java-5.1.6 ( Revision: ${svn.Revision} )
Mar 17, 2010 8:31:23 AM org.hibernate.dialect.Dialect <init>
INFO: Using dialect: org.hibernate.dialect.MySQLDialect
Mar 17, 2010 8:31:23 AM org.hibernate.transaction.TransactionFactoryFactory buildTransactionFactory
INFO: Using default transaction strategy (direct JDBC transactions)
Mar 17, 2010 8:31:23 AM org.hibernate.transaction.TransactionManagerLookupFactory getTransactionManagerLookup
INFO: No TransactionManagerLookup configured (in JTA environment, use of read-write or transactional second-level cache is not recommended)
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Automatic flush during beforeCompletion(): disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Automatic session close at end of transaction: disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: JDBC batch size: 15
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: JDBC batch updates for versioned data: disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Scrollable result sets: enabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: JDBC3 getGeneratedKeys(): enabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Connection release mode: auto
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Maximum outer join fetch depth: 2
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Default batch fetch size: 1
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Generate SQL with comments: disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Order SQL updates by primary key: disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Order SQL inserts for batching: disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory createQueryTranslatorFactory
INFO: Query translator: org.hibernate.hql.ast.ASTQueryTranslatorFactory
Mar 17, 2010 8:31:23 AM org.hibernate.hql.ast.ASTQueryTranslatorFactory <init>
INFO: Using ASTQueryTranslatorFactory
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Query language substitutions: {}
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: JPA-QL strict compliance: disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Second-level cache: enabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Query cache: disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory createCacheProvider
INFO: Cache provider: org.hibernate.cache.NoCacheProvider
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Optimize cache for minimal puts: disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Structured second-level cache entries: disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Echoing all SQL to stdout
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Statistics: disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Deleted entity synthetic identifier rollback: disabled
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Default entity-mode: pojo
Mar 17, 2010 8:31:23 AM org.hibernate.cfg.SettingsFactory buildSettings
INFO: Named query checking : enabled
Mar 17, 2010 8:31:23 AM org.hibernate.impl.SessionFactoryImpl <init>
INFO: building session factory
Mar 17, 2010 8:31:23 AM org.hibernate.impl.SessionFactoryObjectFactory addInstance
INFO: Not binding factory to JNDI, no JNDI name configured
Hibernate: insert into school.exam_detail (fullName, numberOfQuestions, passingPercentage) values (?, ?, ?)
Hibernate: insert into school.exam (detail_id, shortName) values (?, ?)
user saved
java.lang.NullPointerException
        at my.Exam.main(Exam.java:82)
BUILD SUCCESSFUL (total time: 1 second)

anyway nullpointer means it doesn't make session?

[Samanthi perera]

It can't be JNDI problem
i am using same connection to run this example too.Still it runs well

package my;

import java.io.Serializable;
import javax.persistence.*;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.AnnotationConfiguration;

@Entity
public class Thing implements Serializable {

    private long id;
    private String name;
    private ThingDetail thingDetail;

    @Embedded
    public ThingDetail getThingDetail() {
        return thingDetail;
    }

    public void setThingDetail(ThingDetail detail) {
        this.thingDetail = detail;
    }

    @Id
    @GeneratedValue
    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public static void main(String args[]) {
        // Session session = HibernateUtil.getSessionFactory().openSession();
        AnnotationConfiguration config = new AnnotationConfiguration();
        config.addAnnotatedClass(Thing.class);
        SessionFactory sessionFack = config.configure().buildSessionFactory();
        //SessionFactory sessionFack = new AnnotationConfiguration().configure().buildSessionFactory();
        Session session = sessionFack.openSession();
        Transaction transaction = null;
        try {
            transaction = session.beginTransaction();
            ThingDetail detail = new ThingDetail();
            detail.setAlias("Joey Shabidoo");
            detail.setCount(10);

            Thing thing = new Thing();
            thing.setName("Homer");
            thing.setThingDetail(detail);

            session.save(thing);
            System.out.println("user saved");
            transaction.commit();
            System.out.println("transaction successful!!!");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

package my;

import java.io.Serializable;
import javax.persistence.Embeddable;

@Embeddable
public class ThingDetail implements Serializable {

	private String alias;
	private int count;

	public String getAlias() {return alias;}
	public void setAlias(String alias) {
		this.alias = alias;
	}

	public int getCount() {return count;}
	public void setCount(int count) {
		this.count = count;
	}
}

here is my config file

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/school</property>
    <property name="hibernate.connection.username">root</property>
    <property name="hibernate.connection.password">root</property>
    <property name="hibernate.show_sql">true</property>
    <property name="hibernate.current_session_context_class">thread</property>
    <!-- <mapping resource="people/User.hbm.xml"/> -->
    <mapping class="my.User"/> 
   </session-factory> 
</hibernate-configuration>

Both of these examples are in same project.So they use same database connection and same schema.
But different tables

[Christian Dillinger]

I don't know if you changed your original sample, but here you never set transaction. So it's okay that you get a NPE.

#  public static void main(String args[]) {  
#         // Session session = HibernateUtil.getSessionFactory().openSession();  
#         AnnotationConfiguration config = new AnnotationConfiguration();  
#         config.addAnnotatedClass(Exam.class);  
#         config.addAnnotatedClass(ExamDetail.class);  
#         SessionFactory sessionFack = config.configure().buildSessionFactory();  
#         //SessionFactory sessionFack = new AnnotationConfiguration().configure().buildSessionFactory();  
#         Session session = sessionFack.openSession();  
#         Transaction transaction = null;  
#         try {  
#             Exam exam = new Exam();  
#             exam.setShortName("SCJA");  
#   
#             ExamDetail detail = new ExamDetail();  
#             detail.setFullName("Sun Certified Java Associate");  
#             detail.setPassingPercentage(62);  
#             detail.setNumberOfQuestions(55);  
#             exam.setDetail(detail);  
#   
#   
#             session.save(exam);  
#              session.save(detail);  
#             System.out.println("user saved");  
#             transaction.commit();  
#             System.out.println("transaction successful!!!");  
#         } catch (Exception e) {  
#             e.printStackTrace();  
#         }  
#     }  

In your last post you had "transaction = session.beginTransaction()".

[Samanthi perera]

Thnks Christian Dillinger.
You are correct.
I missed that.