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hibernate-database: How to configure multiple database in Hibernate?

I want to use multiple databases in my hibernate application. Please give me an example using multiple database in hibernate.

hibernate x 23
database x 10
Posted On : 2014-11-25 13:14:51.0
profile Garima Gupta - anyforum.in Garima Gupta
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Answers


Hibernate is designed to be used with a large set of databases. The details of those databases are configured in an XML file called hibernate.cfg.xml. This configuration files could be given any name and is usually placed in the root of your application class path. There are many configuration parameters available that makes the mapping of domain model to relational model easier. The same configurations can be done from your Java class uning org.hibernate.cfg.Configuration class.


Let´s Consider an example for Persistent class named Employee:
-----------------------------------------------------------------------------------------------------------


Employee.java:
---------------------------------------------
package hibernatepack.samples;

public class Employee {
private int empid;
private String empname;
private double salary;
public int getEmpid() {
return empid;
}
public void setEmpid(int empid) {
this.empid = empid;
}

public String getEmpname() {
return empname;
}

public void setEmpname(String empname) {
this.empname = empname;
}

public double getSalary() {
return salary;
}

public void setSalary(double salary) {
this.salary = salary;
}
}



The mapping details of the Employee class are available in the Employee.hbm.xml file:
------------------------------------------------------------------------------------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="hibernatepack.samples.Employee" table="HBEmployeeDetails" >
<id name= "empid" column="EmpNo" />
<property name= "empname" column = "EmpName" />
<property name="salary" column="Salary" />
</class>
</hibernate-mapping>


Since we need to persist the Employee object both in Oracle and in Derby, we need to create 2 configuration files ? one for Oracle and another one for Derby.


oracleconfig.cfg.xml:
---------------------------------------------
<?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.OracleDialect</property>
<property name="hibernate.connection.driver_class">oracle.jdbc.OracleDriver</property>
<property name="hibernate.connection.url">jdbc:oracle:thin:@10.154.117.76:1521:oracle</property>
<property name="hibernate.connection.username">user</property>
<property name="hibernate.connection.password">password</property>
<property name="hibernate.hbm2ddl.auto">create</property>
<property name="hibernate.show_sql">true</property>
<mapping resource="Employee.hbm.xml" />
</session-factory>
</hibernate-configuration>


derbiconfig.cfg.xml:
--------------------------------------------
<?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.DerbyDialect</property>
<property name="hibernate.connection.driver_class">org.apache.derby.jdbc.ClientDriver</property>
<property name="hibernate.connection.url">jdbc:derby://localhost:1527/HibernateDB</property>
<property name="hibernate.connection.username">user</property>
<property name="hibernate.connection.password">pwd</property>
<property name="hibernate.show_sql">true</property>
<property name="hibernate.hbm2ddl.auto">create</property>
<mapping resource="Employee.hbm.xml"/>
</session-factory>
</hibernate-configuration>


The IEmployeeDAO.java lists the operations on the Employee object:
----------------------------------------------------------------------------------------------------

package hibernatepack.samples;

import java.util.List;
public interface IEmployeeDAO {
public void findAllEmployees();
public void insertEmployee(Employee e);
}
Let us Implement the above interface using a class :
EmloyeeDaoImpl.java
public class EmployeeDaoImpl implements IEmployeeDAO {
//For using Oracle database
SessionFactory sessionFactory1 = new Configuration().configure("oracleconfig.cfg.xml").buildSessionFactory();
//For using Derby database
SessionFactory sessionFactory2 = new Configuration().configure("derbyconfig.cfg.xml").buildSessionFactory();
Session session = null;
Transaction transaction = null;
public void findAllEmployees() {
ArrayList empList = new ArrayList();
try {
session = sessionFactory1.openSession();
transaction = session.beginTransaction();
transaction.begin();
Criteria crit = session.createCriteria(Employee.class);
empList = (ArrayList) crit.list();
System.out.println("Records from Oracle Database");
for (Employee emp : empList) {
System.out.println(emp.getEmpid() + " " + emp.getEmpname() + " " + emp.getSalary());

}
session.close();
session = sessionFactory2.openSession();
Criteria crit1 = session.createCriteria(Employee.class);
empList = (ArrayList) crit1.list();
System.out.println("Records from Derby Database");
for (Employee emp : empList) {
System.out.println(emp.getEmpid() + " " + emp.getEmpname() + " " + emp.getSalary());
}
session.close();
} catch (Exception he) {
he.printStackTrace();
}
}
public void insertEmployee(Employee e) {
try {
session = sessionFactory1.openSession();
transaction = session.beginTransaction();
transaction.begin();
session.save(e);
transaction.commit();
session.close();
session = sessionFactory2.openSession();
transaction = session.beginTransaction();
transaction.begin();
session.save(e);
transaction.commit();
session.close();
} catch (HibernateException he) {
he.printStackTrace();
}
}
}



Creating Session Factory object in Hibernate Each database has its own SessionFactory object.
SessionFactory sessionFactory1 = new Configuration().configure("oracleconfig.cfg.xml").buildSessionFactory();
SessionFactory sessionFactory2 = new Configuration().configure("derbyconfig.cfg.xml").buildSessionFactory();
Specify the name of the configuration file as an argument to the configure() method when building the session factory object.

Let us create the test application.

EmployeeTest.java:
-------------------------------------------

package hibernatepack.samples;

import java.awt.Choice;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class EmployeeTest {
private static int choice;
public static void main(String[] args) {
EmployeeDaoImpl empOperations = new EmployeeDaoImpl();
Employee e1 = new Employee();
do {
System.out.println("1. Insert ");
System.out.println("2. List ");
System.out.println("3. Exit ");
System.out.println("Enter your choice ");
Scanner sc = new Scanner(System.in);
choice = sc.nextInt();
switch (choice) {
case 1:
System.out.println("Enter the employee Number ");
Scanner sc1 = new Scanner(System.in);
int empid = sc1.nextInt();
System.out.println("Enter the employee Name ");
Scanner sc2 = new Scanner(System.in);
String empname = sc2.nextLine();
System.out.println("Enter the Salary ");
Scanner sc3 = new Scanner(System.in);
double empsal = sc3.nextDouble();
e1.setEmpid(empid);
e1.setEmpname(empname);
e1.setSalary(empsal);
empOperations.insertEmployee(e1);
break;
case 2:
empOperations.findAllEmployees();
break;
}
} while (choice != 3);
}
}

When you execute the insert method, table named "HBEMPLOYEEDETAILS" is created both in Oracle and in Derby.

Posted On : 2014-11-25 13:29:09
Satisfied : 2 Yes  0 No
profile Rishi Kumar - anyforum.in Rishi Kumar
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