Program to demonstrate how to retrieve an object from database by primary key using Hibernate Framework.
A simple POJO class (model) Customer.java, whose object we want to store and than retrieve back using primary key from database using Hibernate.
Hibernate Configuration XML file
A simple test class to save and than retrieve an object from database using the primary key.
Output of the program :
A simple POJO class (model) Customer.java, whose object we want to store and than retrieve back using primary key from database using Hibernate.
package com.hubberspot.hibernate.examples; import javax.persistence.Entity; import javax.persistence.Id; // @Entity to tell Hibernate that we need this Model // class to get store in database as a table by name // Customer @Entity public class Customer { // @Id to tell Hibernate that we need this Model // class having customerId as a Primary Key in the // table Customer created by @Entity @Id private int customerId; private String customerName; public int getUserId() { return customerId; } public void setUserId(int userId) { this.customerId = userId; } public String getUserName() { return customerName; } public void setUserName(String userName) { this.customerName = userName; } }
Hibernate Configuration XML 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="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost/customerdb</property> <property name="connection.username">root</property> <property name="connection.password">root</property> <!-- SQL dialect --> <property name="dialect"> org.hibernate.dialect.MySQL5Dialect </property> <!-- Drop and re-create the database schema on startup --> <property name="hbm2ddl.auto">create</property> <!-- Mapping class entry into configuration xml for annotated classes --> <mapping class="com.hubberspot.hibernate.examples.Customer" /> </session-factory> </hibernate-configuration> |
A simple test class to save and than retrieve an object from database using the primary key.
package com.hubberspot.hibernate.examples; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; public class HibernateTest { public static void main(String[] args) { // Lets create a Customer Object Customer customer = new Customer(); customer.setUserId(1); customer.setUserName("Jonty"); // SessionFactory gives us a factory of sessions // Usually SessionFactory is been configured by the // configuration file named as hibernate.cfg.xml // buildSessionFactory() builds the sessionFactory for us SessionFactory sessionFactory = new Configuration(). configure().buildSessionFactory(); // Session is created by calling openSession() // method on SessionFactory object Session session = sessionFactory.openSession(); session.beginTransaction(); // Our Transaction Code goes here // i.e save, load , merge and remove // Lets save our Customer object created // above using sessions save method. session.save(customer); // Committing the transaction in order to save. session.getTransaction().commit(); // Closing the session session.close(); // Pointing the customer to null in order to // demonstrate how to fetch / retrieve the object customer = null; // again opening a session from SessionFactory session = sessionFactory.openSession(); session.beginTransaction(); // We use get method of the session for retrieving // the object from the database if we know the primary key // for which we want to retrieve. // The get method takes in two arguments one is class object // for which we want to fetch record and second is the // primary key. customer = (Customer) session.get(Customer.class, 1); // finally printing the retrieved customer name based on the // primary key passed System.out.println("Customer Name retrived is : " + customer.getUserName()); } }
Output of the program :