Java and Flex Integration Bible by Keefe Matthew Christiansen Charles A

Author:Keefe, Matthew, Christiansen, Charles A.
Language: eng
Format: epub
Publisher: John Wiley & Sons, Inc.
Published: 2010-03-09T16:00:00+00:00

Here's the code listing for the ListAllPetsUsingHibernate class:

/**

*

*/

package com.wiley.jfib.ch09;

import java.util.List;

import org.hibernate.HibernateException;

import org.hibernate.SessionFactory;

import org.hibernate.Transaction;

import org.hibernate.cfg.Configuration;

import org.hibernate.classic.Session;

/**

* @author Chuck

* The ListAllPetsUsingHibernate class retrieves all of the pets from the

* PETS table in the database and lists the name, type, and

* owner's name for each one.

*/

public class ListAllPetsUsingHibernate {

/**

* @param args Any arguments passed to this application.

* This application expects and uses no arguments.

*/

public static void main(String[] args)

{

try

{

// Set up the Hibernate session

Configuration config = new Configuration();

config.configure(“hibernate.cfg.xml”);

SessionFactory sessionFactory = config.buildSessionFactory();

Session session = sessionFactory.getCurrentSession();

Transaction tx = session.beginTransaction();

// get the current list of pets and owners

List<Pet> allPets = session.createCriteria(Pet.class).list();

for(Pet pet : allPets)

{

// print out each pet in the list

System.out.println(pet.getName()

+ “ is a “ + pet.getType()

+ “ belonging to “

+ pet.getPerson().getFirstName() + “ “ + pet.getPerson().getLastName());

}

tx.commit();

}

catch (HibernateException e)

{

e.printStackTrace();

}

}

}

At the beginning of this class, a number of Hibernate classes are imported. Configuration is used to read the configuration from the hibernate.cfg.xml file. SessionFactory uses this configuration to create a Session class. Transaction is a class that Hibernate provides for transaction management, which is a way of grouping operations into a single unit so that they all succeed or fail as one. Finally, any errors that occur within Hibernate code result in a HibernateException being thrown.

In the main method of this class, the Hibernate session is created by the SessionFactory by using the information from the Configuration object config. A transaction is started by the session — although, in reality, a session doesn't serve much purpose here with only a single operation being run; Hibernate requires some sort of transaction management to be in place.

This line of code does the bulk of the work:

List<Pet> allPets = session.createCriteria(Pet.class).list();

The Hibernate Session object has a variety of methods for retrieving objects. For retrieving single objects whose primary key value (for example, PET_ID) is known, you would use the load() method and supply it with the class of the Pet object and the primary key value. To retrieve a list of all objects of a given class, you would use a line like the one just presented. This line says to get a list of every Pet object from the database. Hibernate goes to the database and retrieves not only all the pets, but because of the many-to-one relationship you set up in the Hibernate mapping file between Pet and Person, it also populates the Person object property in the Pet object. The type List<Pet> indicates that this List object contains only Pets. The loop takes each Pet object in the list and prints out the pet's name and type, but thanks to the many-to-one relationship, it can also print out the owner's first and last names.

To run the application, right-click the ListAllPetsUsingHibernate.java file in the Project Explorer and then choose Run As⇒Java Application from the popup menu. You should see the program's output in the Console view, as shown in Figure 9.

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