Question
I'm so lost on how to do this question, and I have to get it right to get a b. Please help me. Create a Employee class with the following: A private String variable named
Explanation / Answer
public class Employee { private int id; private String firstName; private String lastName; private int salary; 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; } } Let us create the following EMPLOYEE table to store Employee objects: 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) ); Following will be mapping file. This class contains the employee detail. Finally, we will create our application class with the main() method to run the application where we will use Native SQL queries: import java.util.*; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.Transaction; import org.hibernate.SessionFactory; import org.hibernate.SQLQuery; import org.hibernate.Criteria; import org.hibernate.Hibernate; 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(); /* Add few employee records in database */ Integer empID1 = ME.addEmployee("Zara", "Ali", 2000); Integer empID2 = ME.addEmployee("Daisy", "Das", 5000); Integer empID3 = ME.addEmployee("John", "Paul", 5000); Integer empID4 = ME.addEmployee("Mohd", "Yasee", 3000); /* List down employees and their salary using Scalar Query */ ME.listEmployeesScalar(); /* List down complete employees information using Entity Query */ ME.listEmployeesEntity(); } /* Method to CREATE an employee in the database */ public Integer addEmployee(String fname, String lname, int salary){ Session session = factory.openSession(); Transaction tx = null; Integer employeeID = null; try{ tx = session.beginTransaction(); Employee employee = new Employee(fname, lname, salary); employeeID = (Integer) session.save(employee); tx.commit(); }catch (HibernateException e) { if (tx!=null) tx.rollback(); e.printStackTrace(); }finally { session.close(); } return employeeID; } /* Method to READ all the employees using Scalar Query */ public void listEmployeesScalar( ){ Session session = factory.openSession(); Transaction tx = null; try{ tx = session.beginTransaction(); String sql = "SELECT first_name, salary FROM EMPLOYEE"; SQLQuery query = session.createSQLQuery(sql); query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP); List data = query.list(); for(Object object : data) { Map row = (Map)object; System.out.print("First Name: " + row.get("first_name")); System.out.println(", Salary: " + row.get("salary")); } tx.commit(); }catch (HibernateException e) { if (tx!=null) tx.rollback(); e.printStackTrace(); }finally { session.close(); } } /* Method to READ all the employees using Entity Query */ public void listEmployeesEntity( ){ Session session = factory.openSession(); Transaction tx = null; try{ tx = session.beginTransaction(); String sql = "SELECT * FROM EMPLOYEE"; SQLQuery query = session.createSQLQuery(sql); query.addEntity(Employee.class); List employees = query.list(); for (Iterator iterator = employees.iterator(); iterator.hasNext();){ Employee employee = (Employee) iterator.next(); System.out.print("First Name: " + employee.getFirstName()); System.out.print(" Last Name: " + employee.getLastName()); System.out.println(" Salary: " + employee.getSalary()); } tx.commit(); }catch (HibernateException e) { if (tx!=null) tx.rollback(); e.printStackTrace(); }finally { session.close(); } } } Compilation and Execution: Here are the steps to compile and run the above mentioned application. Make sure you have set PATH and CLASSPATH appropriately before proceeding for the compilation and execution. 1. Create hibernate.cfg.xml configuration file as explained in configuration chapter. 2. Create Employee.hbm.xml mapping file as shown above. 3. Create Employee.java source file as shown above and compile it. 4. Create ManageEmployee.java source file as shown above and compile it. 5. Execute ManageEmployee binary to run the program. You would get following result, and records would be created in EMPLOYEE table. $java ManageEmployee .......VARIOUS LOG MESSAGES WILL DISPLAY HERE........ First Name: Zara, Salary: 2000 First Name: Daisy, Salary: 5000 First Name: John, Salary: 5000 First Name: Mohd, Salary: 3000 First Name: Zara Last Name: Ali Salary: 2000 First Name: Daisy Last Name: Das Salary: 5000 First Name: John Last Name: Paul Salary: 5000 First Name: Mohd Last Name: Yasee Salary: 3000 If you check your EMPLOYEE table, it should have following records: mysql> select * from EMPLOYEE; +----+------------+-----------+--------+ | id | first_name | last_name | salary | +----+------------+-----------+--------+ | 26 | Zara | Ali | 2000 | | 27 | Daisy | Das | 5000 | | 28 | John | Paul | 5000 | | 29 | Mohd | Yasee | 3000 | +----+------------+-----------+--------+ 4 rows in set (0.00 sec) mysql>