create table EMPLOYEE (
  id INT NOT NULL auto_increment,
  first_name VARCHAR(20) default NULL,
  last_name VARCHAR(20) default NULL,
  salary   INT default NULL,
  PRIMARY KEY (id)
);

create table CERTIFICATE (
  id INT NOT NULL auto_increment,
  certificate_type VARCHAR(40) default NULL,
  certificate_name VARCHAR(30) default NULL,
  employee_id INT default NULL,
  PRIMARY KEY (id)
);

import java.util.*;

public class Employee {
  private int id;
  private String firstName; 
  private String lastName;  
  private int salary;
  private Map certificates;

  public Employee() {}
  public Employee(String fname, String lname, int salary) {
   this.firstName = fname;
   this.lastName = lname;
   this.salary = salary;
  }
  public int getId() {
   return id;
  }
  public void setId( int id ) {
   this.id = id;
  }
  public String getFirstName() {
   return firstName;
  }
  public void setFirstName( String first_name ) {
   this.firstName = first_name;
  }
  public String getLastName() {
   return lastName;
  }
  public void setLastName( String last_name ) {
   this.lastName = last_name;
  }
  public int getSalary() {
   return salary;
  }
  public void setSalary( int salary ) {
   this.salary = salary;
  }

  public Map getCertificates() {
   return certificates;
  }
  public void setCertificates( Map certificates ) {
   this.certificates = certificates;
  }
}

public class Certificate{
  private int id;
  private String name; 

  public Certificate() {}
  public Certificate(String name) {
   this.name = name;
  }
  public int getId() {
   return id;
  }
  public void setId( int id ) {
   this.id = id;
  }
  public String getName() {
   return name;
  }
  public void setName( String name ) {
   this.name = name;
  }
}

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
 "-//Hibernate/Hibernate Mapping DTD//EN"
 "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> 

<hibernate-mapping>
  <class name="Employee" table="EMPLOYEE">
   <meta attribute="class-description">
     This class contains the employee detail. 
   </meta>
   <id name="id" type="int" column="id">
     <generator class="native"/>
   </id>
   <map name="certificates" cascade="all">
     <key column="employee_id"/>
     <index column="certificate_type" type="string"/>
     <one-to-many class="Certificate"/>
   </map>
   <property name="firstName" column="first_name" type="string"/>
   <property name="lastName" column="last_name" type="string"/>
   <property name="salary" column="salary" type="int"/>
  </class>

  <class name="Certificate" table="CERTIFICATE">
   <meta attribute="class-description">
     This class contains the certificate records. 
   </meta>
   <id name="id" type="int" column="id">
     <generator class="native"/>
   </id>
   <property name="name" column="certificate_name" type="string"/>
  </class>

</hibernate-mapping>

import java.util.*;
 
import org.hibernate.HibernateException; 
import org.hibernate.Session; 
import org.hibernate.Transaction;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class ManageEmployee {
  private static SessionFactory factory; 
  public static void main(String[] args) {
   try{
     factory = new Configuration().configure().buildSessionFactory();
   }catch (Throwable ex) { 
     System.err.println("Failed to create sessionFactory object." + ex);
     throw new ExceptionInInitializerError(ex); 
   }
   ManageEmployee ME = new ManageEmployee();
   /* Let us have a set of certificates for the first employee */
   HashMap set = new HashMap();
   set.put("ComputerScience", new Certificate("MCA"));
   set.put("BusinessManagement", new Certificate("MBA"));
   set.put("ProjectManagement", new Certificate("PMP"));
   
   /* Add employee records in the database */
   Integer empID = ME.addEmployee("Manoj", "Kumar", 4000, set);

   /* List down all the employees */
   ME.listEmployees();

   /* Update employee's salary records */
   ME.updateEmployee(empID, 5000);

   /* List down all the employees */
   ME.listEmployees();

  }

  /* Method to add an employee record in the database */
  public Integer addEmployee(String fname, String lname, 
                   int salary, HashMap cert){
   Session session = factory.openSession();
   Transaction tx = null;
   Integer employeeID = null;
   try{
     tx = session.beginTransaction();
     Employee employee = new Employee(fname, lname, salary);
     employee.setCertificates(cert);
     employeeID = (Integer) session.save(employee); 
     tx.commit();
   }catch (HibernateException e) {
     if (tx!=null) tx.rollback();
     e.printStackTrace(); 
   }finally {
     session.close(); 
   }
   return employeeID;
  }

  /* Method to list all the employees detail */
  public void listEmployees( ){
   Session session = factory.openSession();
   Transaction tx = null;
   try{
     tx = session.beginTransaction();
     List employees = session.createQuery("FROM Employee").list(); 
     for (Iterator iterator1 = 
              employees.iterator(); iterator1.hasNext();){
      Employee employee = (Employee) iterator1.next(); 
      System.out.print("First Name: " + employee.getFirstName()); 
      System.out.print(" Last Name: " + employee.getLastName()); 
      System.out.println(" Salary: " + employee.getSalary());
      Map ec = employee.getCertificates();
      System.out.println("Certificate: " + 
       (((Certificate)ec.get("ComputerScience")).getName()));
      System.out.println("Certificate: " + 
       (((Certificate)ec.get("BusinessManagement")).getName()));
      System.out.println("Certificate: " + 
       (((Certificate)ec.get("ProjectManagement")).getName()));
     }
     tx.commit();
   }catch (HibernateException e) {
     if (tx!=null) tx.rollback();
     e.printStackTrace(); 
   }finally {
     session.close(); 
   }
  }
  /* Method to update salary for an employee */
  public void updateEmployee(Integer EmployeeID, int salary ){
   Session session = factory.openSession();
   Transaction tx = null;
   try{
     tx = session.beginTransaction();
     Employee employee = 
          (Employee)session.get(Employee.class, EmployeeID); 
     employee.setSalary( salary );
     session.update(employee);
     tx.commit();
   }catch (HibernateException e) {
     if (tx!=null) tx.rollback();
     e.printStackTrace(); 
   }finally {
     session.close(); 
   }
  }
  /* Method to delete an employee from the records */
  public void deleteEmployee(Integer EmployeeID){
   Session session = factory.openSession();
   Transaction tx = null;
   try{
     tx = session.beginTransaction();
     Employee employee = 
          (Employee)session.get(Employee.class, EmployeeID); 
     session.delete(employee); 
     tx.commit();
   }catch (HibernateException e) {
     if (tx!=null) tx.rollback();
     e.printStackTrace(); 
   }finally {
     session.close(); 
   }
  }
}

$java ManageEmployee

First Name: Manoj Last Name: Kumar Salary: 4000
Certificate: MCA
Certificate: MBA
Certificate: PMP
First Name: Manoj Last Name: Kumar Salary: 5000
Certificate: MCA
Certificate: MBA
Certificate: PMP

mysql> select * from EMPLOYEE;

+----+------------+-----------+--------+
| id | first_name | last_name | salary |
+----+------------+-----------+--------+
| 60 | Manoj   | Kumar   |  5000 |
+----+------------+-----------+--------+
1 row in set (0.00 sec)

mysql>select * from CERTIFICATE;

+----+--------------------+------------------+-------------+
| id | certificate_type  | certificate_name | employee_id |
+----+--------------------+------------------+-------------+
| 16 | ProjectManagement | PMP       |     60 |
| 17 | BusinessManagement | MBA       |     60 |
| 18 | ComputerScience  | MCA       |     60 |
+----+--------------------+------------------+-------------+
3 rows in set (0.00 sec)

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
 "-//Hibernate/Hibernate Mapping DTD//EN"
 "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> 

<hibernate-mapping>
  <class name="Employee" table="EMPLOYEE">
   <meta attribute="class-description">
     This class contains the employee detail. 
   </meta>
   <id name="id" type="int" column="id">
     <generator class="native"/>
   </id>
   <map name="certificates" cascade="all" sort="MyClass">
     <key column="employee_id"/>
     <index column="certificate_type" type="string"/>
     <one-to-many class="Certificate"/>
   </map>
   <property name="firstName" column="first_name" type="string"/>
   <property name="lastName" column="last_name" type="string"/>
   <property name="salary" column="salary" type="int"/>
  </class>

  <class name="Certificate" table="CERTIFICATE">
   <meta attribute="class-description">
     This class contains the certificate records. 
   </meta>
   <id name="id" type="int" column="id">
     <generator class="native"/>
   </id>
   <property name="name" column="certificate_name" type="string"/>
  </class>

</hibernate-mapping>

import java.util.Comparator;

public class MyClass implements Comparator <String>{
  public int compare(String o1, String o2) {
   final int BEFORE = -1;
   final int AFTER = 1;

   /* To reverse the sorting order, multiple by -1 */
   if (o2 == null) {
     return BEFORE * -1;
   }

   Comparable thisCertificate = o1;
   Comparable thatCertificate = o2;

   if(thisCertificate == null) {
     return AFTER * 1;
   } else if(thatCertificate == null) {
     return BEFORE * -1;
   } else {
     return thisCertificate.compareTo(thatCertificate) * -1;
   }
  }
}

import java.util.*;
 
import org.hibernate.HibernateException; 
import org.hibernate.Session; 
import org.hibernate.Transaction;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class ManageEmployee {
  private static SessionFactory factory; 
  public static void main(String[] args) {
   try{
     factory = new Configuration().configure().buildSessionFactory();
   }catch (Throwable ex) { 
     System.err.println("Failed to create sessionFactory object." + ex);
     throw new ExceptionInInitializerError(ex); 
   }
   ManageEmployee ME = new ManageEmployee();
   /* Let us have a set of certificates for the first employee */
   TreeMap set1 = new TreeMap();
   set1.put("ComputerScience", new Certificate("MCA"));
   set1.put("BusinessManagement", new Certificate("MBA"));
   set1.put("ProjectManagement", new Certificate("PMP"));
 
   /* Add employee records in the database */
   Integer empID1 = ME.addEmployee("Manoj", "Kumar", 4000, set1);

   /* Another set of certificates for the second employee */
   TreeMap set2 = new TreeMap();
   set2.put("ComputerScience", new Certificate("MCA"));
   set2.put("BusinessManagement", new Certificate("MBA"));

   /* Add another employee record in the database */
   Integer empID2 = ME.addEmployee("Dilip", "Kumar", 3000, set2);

   /* List down all the employees */
   ME.listEmployees();

   /* Update employee's salary records */
   ME.updateEmployee(empID1, 5000);

   /* Delete an employee from the database */
   ME.deleteEmployee(empID2);

   /* List down all the employees */
   ME.listEmployees();

  }

  /* Method to add an employee record in the database */
  public Integer addEmployee(String fname, String lname, 
                   int salary, TreeMap cert){
   Session session = factory.openSession();
   Transaction tx = null;
   Integer employeeID = null;
   try{
     tx = session.beginTransaction();
     Employee employee = new Employee(fname, lname, salary);
     employee.setCertificates(cert);
     employeeID = (Integer) session.save(employee); 
     tx.commit();
   }catch (HibernateException e) {
     if (tx!=null) tx.rollback();
     e.printStackTrace(); 
   }finally {
     session.close(); 
   }
   return employeeID;
  }

  /* Method to list all the employees detail */
  public void listEmployees( ){
   Session session = factory.openSession();
   Transaction tx = null;
   try{
     tx = session.beginTransaction();
     List employees = session.createQuery("FROM Employee").list(); 
     for (Iterator iterator1 = 
              employees.iterator(); iterator1.hasNext();){
      Employee employee = (Employee) iterator1.next(); 
      System.out.print("First Name: " + employee.getFirstName()); 
      System.out.print(" Last Name: " + employee.getLastName()); 
      System.out.println(" Salary: " + employee.getSalary());
      SortedMap<String, Certificate> map = 
                        employee.getCertificates();
      for(Map.Entry<String,Certificate> entry : map.entrySet()){
        System.out.print("\tCertificate Type: " + entry.getKey());
        System.out.println(", Name: " + 
                    (entry.getValue()).getName());
      }
     }
     tx.commit();
   }catch (HibernateException e) {
     if (tx!=null) tx.rollback();
     e.printStackTrace(); 
   }finally {
     session.close(); 
   }
  }
  /* Method to update salary for an employee */
  public void updateEmployee(Integer EmployeeID, int salary ){
   Session session = factory.openSession();
   Transaction tx = null;
   try{
     tx = session.beginTransaction();
     Employee employee = 
          (Employee)session.get(Employee.class, EmployeeID); 
     employee.setSalary( salary );
     session.update(employee);
     tx.commit();
   }catch (HibernateException e) {
     if (tx!=null) tx.rollback();
     e.printStackTrace(); 
   }finally {
     session.close(); 
   }
  }
  /* Method to delete an employee from the records */
  public void deleteEmployee(Integer EmployeeID){
   Session session = factory.openSession();
   Transaction tx = null;
   try{
     tx = session.beginTransaction();
     Employee employee = 
          (Employee)session.get(Employee.class, EmployeeID); 
     session.delete(employee); 
     tx.commit();
   }catch (HibernateException e) {
     if (tx!=null) tx.rollback();
     e.printStackTrace(); 
   }finally {
     session.close(); 
   }
  }
}

$java ManageEmployee

.......VARIOUS LOG MESSAGES WILL DISPLAY HERE........

First Name: Manoj Last Name: Kumar Salary: 4000
 Certificate Type: ProjectManagement, Name: PMP
 Certificate Type: ComputerScience, Name: MCA
 Certificate Type: BusinessManagement, Name: MBA
First Name: Dilip Last Name: Kumar Salary: 3000
 Certificate Type: ComputerScience, Name: MCA
 Certificate Type: BusinessManagement, Name: MBA
First Name: Manoj Last Name: Kumar Salary: 5000
 Certificate Type: ProjectManagement, Name: PMP
 Certificate Type: ComputerScience, Name: MCA
 Certificate Type: BusinessManagement, Name: MBA

mysql> select * from EMPLOYEE;

+----+------------+-----------+--------+
| id | first_name | last_name | salary |
+----+------------+-----------+--------+
| 74 | Manoj   | Kumar   |  5000 |
+----+------------+-----------+--------+
1 row in set (0.00 sec)

mysql> select * from CERTIFICATE;

+----+--------------------+------------------+-------------+
| id | certificate_type  | certificate_name | employee_id |
+----+--------------------+------------------+-------------+
| 52 | BusinessManagement | MBA       |     74 |
| 53 | ComputerScience  | MCA       |     74 |
| 54 | ProjectManagement | PMP       |     74 |
+----+--------------------+------------------+-------------+
3 rows in set (0.00 sec)