First Hibernate CRUD Practical Example

Hibernate Practical Example

An example of using Hibernate to provide Java persistence in a standalone application. We will go through different steps involved in creating Java Application using Hibernate technology.

The first step in creating an application is to build the Java POJO class or classes, depending on the application that will be persisted to the database. Let us consider our Employee class with getXXX and setXXX methods to make it JavaBeans compliant class.

A POJO (Plain Old Java Object) is a Java object that doesn't extend or implement some specialized classes and interfaces respectively required by the EJB framework. All normal Java objects are POJO.

When you design a class to be persisted by Hibernate, it's important to provide JavaBeans compliant code as well as one attribute which would work as index like id attribute in the Employee class.

Employee.java

package com.smgc;

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;

}

// generate getters and setters

}

Create Database Tables:

Second step would be creating tables in your database. There would be one table corresponding to each object you are willing to provide persistence. Consider above objects need to be stored and retrieved into the following RDBMS table:

Here I take database: test and table: emp

create table emp (

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 Mapping Configuration File:

This step is to create a mapping file that instructs Hibernate how to map the defined class or classes to the database tables. You should save the mapping document in a file with the format <classname>.hbm.xml. We saved our mapping document in the file Employee.hbm.xml.

<?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 package="com.smgc">

This class contains the employee detail.

</meta>

</id>

</class>

</hibernate-mapping>

Let us see little detail about the mapping document:

· The mapping document is an XML document having <hibernate-mapping> as the root element which contains all the <class> elements.

· The <class> elements are used to define specific mappings from a Java classes to the database tables. The Java class name is specified using the name attribute of the class element and the database table name is specified using the table attribute.

· The <meta> element is optional element and can be used to create the class description.

· The <id> element maps the unique ID attribute in class to the primary key of the database table. The name attribute of the id element refers to the property in the class and the column attribute refers to the column in the database table. The type attribute holds the hibernate mapping type, this mapping types will convert from Java to SQL data type.

· The <generator> element within the id element is used to automatically generate the primary key values. Set the class attribute of the generator element is set to native to let hibernate pick up eitheridentity, sequence or hilo algorithm to create primary key depending upon the capabilities of the underlying database.

· The <property> element is used to map a Java class property to a column in the database table. The name attribute of the element refers to the property in the class and the column attribute refers to the column in the database table. The type attribute holds the hibernate mapping type, this mapping types will convert from Java to SQL data type.

Create Application Class:

Finally, we will create our application class with the main() method to run the application. We will use this application to save few Employee's records and then we will apply CRUD operations on those records.

ManageEmployee.java

package com.smgc;

import java.util.Iterator;

import java.util.List;

import org.hibernate.HibernateException;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.Transaction;

import org.hibernate.cfg.Configuration;

public class ManageEmployee {

private static SessionFactory factory;

public static void main(String[] args) {

// TODO Auto-generated method stub

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("Amit", "Patel", 1000);

Integer empID2 = ME.addEmployee("Denis", "Das", 5000);

Integer empID3 = ME.addEmployee("Jenti", "Shah", 10000);

/* List down all the employees */

ME.listEmployees();

/* Update employee's records */

ME.updateEmployee(empID1, 5000);

/* Delete an employee from the database */

ME.deleteEmployee(empID2);

/* List down new list of the employees */

ME.listEmployees();

}

/* 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 */

public void listEmployees() {

Session session = factory.openSession();

Transaction tx = null;

try {

tx = session.beginTransaction();

List employees = session.createQuery("FROM Employee").list();

System.out.println("Employee Details");

System.out.println("First Name Last name Salary");

System.out.println("-------------------------");

for (Iterator iterator = employees.iterator(); iterator.hasNext();) {

Employee employee = (Employee) iterator.next();

System.out.print(employee.getFirstName());

System.out.print("\t" + employee.getLastName());

System.out.println("\t" + employee.getSalary());

}

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();

}

Create Hibernate.cfg.xml Configuration File:

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-configuration SYSTEM

"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

<session-factory>

org.hibernate.dialect.MySQLDialect

</property>

com.mysql.jdbc.Driver

</property>

jdbc:mysql://localhost:3306/test

</property>

root

</property>

</property>

</session-factory>

</hibernate-configuration>

પટેલ સમાજનો ઈતિહાસ જાણો : કોણ અને ક્યાંથી આવ્યા હતા પાટીદારો

June 13, 2018

Search This Blog

IT & Programming Information