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Учебник по примерам критериев гибернации


Добро пожаловать в учебник по примерам критериев гибернации. Сегодня мы рассмотрим критерии в Hibernate.

Критерии гибернации

  1. Hibernate Criteria API предоставляет проекцию, которую мы можем использовать для агрегатных функций, таких как sum(), min(), max() и т. д.
  2. Hibernate Criteria API можно использовать с ProjectionList для выборки только выбранных столбцов.
  3. Критерии в Hibernate можно использовать для запросов на соединение путем объединения нескольких таблиц. Полезными методами для объединения критериев Hibernate являются createAlias(), setFetchMode() и setProjection()
  4. Критерии в Hibernate API можно использовать для получения результатов с условиями, полезными методами являются add(), где мы можем добавлять ограничения.
  5. Hibernate Criteria API предоставляет метод addOrder(), который мы можем использовать для упорядочивания результатов.

Ниже в классе показаны различные варианты использования Hibernate Criteria API, большинство из которых являются заменой примеров в учебнике по HQL.

package com.journaldev.hibernate.main;

import java.util.Arrays;
import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.FetchMode;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.ProjectionList;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Restrictions;

import com.journaldev.hibernate.model.Employee;
import com.journaldev.hibernate.util.HibernateUtil;

public class HibernateCriteriaExamples {

	@SuppressWarnings("unchecked")
	public static void main(String[] args) {
		// Prep work
		SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
		Session session = sessionFactory.getCurrentSession();
		Transaction tx = session.beginTransaction();

		//Get All Employees
		Criteria criteria = session.createCriteria(Employee.class);
		List<Employee> empList = criteria.list();
		for(Employee emp : empList){
			System.out.println("ID="+emp.getId()+", Zipcode="+emp.getAddress().getZipcode());
		}
		
		// Get with ID, creating new Criteria to remove all the settings
		criteria = session.createCriteria(Employee.class)
					.add(Restrictions.eq("id", new Long(3)));
		Employee emp = (Employee) criteria.uniqueResult();
		System.out.println("Name=" + emp.getName() + ", City="
				+ emp.getAddress().getCity());

		//Pagination Example
		empList = session.createCriteria(Employee.class)
					.addOrder(Order.desc("id"))
					.setFirstResult(0)
					.setMaxResults(2)
					.list();
		for(Employee emp4 : empList){
			System.out.println("Paginated Employees::"+emp4.getId()+","+emp4.getAddress().getCity());
		}

		//Like example
		empList = session.createCriteria(Employee.class)
				.add(Restrictions.like("name", "%i%"))
				.list();
		for(Employee emp4 : empList){
			System.out.println("Employees having 'i' in name::"+emp4.getName()+","+emp4.getAddress().getCity());
		}
		
		//Projections example
		long count = (Long) session.createCriteria(Employee.class)
				.setProjection(Projections.rowCount())
				.add(Restrictions.like("name", "%i%"))
				.uniqueResult();
		System.out.println("Number of employees with 'i' in name="+count);

		//using Projections for sum, min, max aggregation functions
		double sumSalary = (Double) session.createCriteria(Employee.class)
			.setProjection(Projections.sum("salary"))
			.uniqueResult();
		System.out.println("Sum of Salaries="+sumSalary);
		
		//Join example for selecting few columns
		criteria = session.createCriteria(Employee.class, "employee");
		criteria.setFetchMode("employee.address", FetchMode.JOIN);
		criteria.createAlias("employee.address", "address"); // inner join by default

		ProjectionList columns = Projections.projectionList()
						.add(Projections.property("name"))
						.add(Projections.property("address.city"));
		criteria.setProjection(columns);

		List<Object[]> list = criteria.list();
		for(Object[] arr : list){
			System.out.println(Arrays.toString(arr));
		}
		
		
		// Rollback transaction to avoid messing test data
		tx.commit();
		// closing hibernate resources
		sessionFactory.close();
	}

}

Когда мы выполняем приведенную выше примерную программу Hibernate Criteria, мы получаем следующий вывод.

May 26, 2014 6:53:32 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit>
INFO: HCANN000001: Hibernate Commons Annotations {4.0.4.Final}
May 26, 2014 6:53:32 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {4.3.5.Final}
May 26, 2014 6:53:32 PM org.hibernate.cfg.Environment <clinit>
INFO: HHH000206: hibernate.properties not found
May 26, 2014 6:53:32 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
May 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration configure
INFO: HHH000043: Configuring from resource: hibernate.cfg.xml
May 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration getConfigurationInputStream
INFO: HHH000040: Configuration resource: hibernate.cfg.xml
May 26, 2014 6:53:32 PM org.hibernate.internal.util.xml.DTDEntityResolver resolveEntity
WARN: HHH000223: Recognized obsolete hibernate namespace https://hibernate.sourceforge.net/. Use namespace https://www.hibernate.org/dtd/ instead. Refer to Hibernate 3.6 Migration Guide!
May 26, 2014 6:53:32 PM org.hibernate.cfg.Configuration doConfigure
INFO: HHH000041: Configured SessionFactory: null
Hibernate Configuration loaded
Hibernate serviceRegistry created
May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH000402: Using Hibernate built-in connection pool (not for production use!)
May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH000401: using driver [com.mysql.jdbc.Driver] at URL [jdbc:mysql://localhost/TestDB]
May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH000046: Connection properties: {user=pankaj, password=****}
May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH000006: Autocommit mode: false
May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
May 26, 2014 6:53:32 PM org.hibernate.dialect.Dialect <init>
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect
May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.internal.LobCreatorBuilder useContextualLobCreation
INFO: HHH000423: Disabling contextual LOB creation as JDBC driver reported JDBC version [3] less than 4
May 26, 2014 6:53:32 PM org.hibernate.engine.transaction.internal.TransactionFactoryInitiator initiateService
INFO: HHH000399: Using default transaction strategy (direct JDBC transactions)
May 26, 2014 6:53:32 PM org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory <init>
INFO: HHH000397: Using ASTQueryTranslatorFactory
Hibernate: select this_.emp_id as emp_id1_1_1_, this_.emp_name as emp_name2_1_1_, this_.emp_salary as emp_sala3_1_1_, address2_.emp_id as emp_id1_0_0_, address2_.address_line1 as address_2_0_0_, address2_.city as city3_0_0_, address2_.zipcode as zipcode4_0_0_ from EMPLOYEE this_ left outer join ADDRESS address2_ on this_.emp_id=address2_.emp_id
ID=1, Zipcode=95129
ID=2, Zipcode=95051
ID=3, Zipcode=560100
ID=4, Zipcode=100100
Hibernate: select this_.emp_id as emp_id1_1_1_, this_.emp_name as emp_name2_1_1_, this_.emp_salary as emp_sala3_1_1_, address2_.emp_id as emp_id1_0_0_, address2_.address_line1 as address_2_0_0_, address2_.city as city3_0_0_, address2_.zipcode as zipcode4_0_0_ from EMPLOYEE this_ left outer join ADDRESS address2_ on this_.emp_id=address2_.emp_id where this_.emp_id=?
Name=Lisa, City=Bangalore
Hibernate: select this_.emp_id as emp_id1_1_1_, this_.emp_name as emp_name2_1_1_, this_.emp_salary as emp_sala3_1_1_, address2_.emp_id as emp_id1_0_0_, address2_.address_line1 as address_2_0_0_, address2_.city as city3_0_0_, address2_.zipcode as zipcode4_0_0_ from EMPLOYEE this_ left outer join ADDRESS address2_ on this_.emp_id=address2_.emp_id order by this_.emp_id desc limit ?
Paginated Employees::4,New Delhi
Paginated Employees::3,Bangalore
Hibernate: select this_.emp_id as emp_id1_1_1_, this_.emp_name as emp_name2_1_1_, this_.emp_salary as emp_sala3_1_1_, address2_.emp_id as emp_id1_0_0_, address2_.address_line1 as address_2_0_0_, address2_.city as city3_0_0_, address2_.zipcode as zipcode4_0_0_ from EMPLOYEE this_ left outer join ADDRESS address2_ on this_.emp_id=address2_.emp_id where this_.emp_name like ?
Employees having 'i' in name::David,Santa Clara
Employees having 'i' in name::Lisa,Bangalore
Hibernate: select count(*) as y0_ from EMPLOYEE this_ where this_.emp_name like ?
Number of employees with 'i' in name=2
Hibernate: select sum(this_.emp_salary) as y0_ from EMPLOYEE this_
Sum of Salaries=1000.0
Hibernate: select this_.emp_name as y0_, address1_.city as y1_ from EMPLOYEE this_ inner join ADDRESS address1_ on this_.emp_id=address1_.emp_id
[Pankaj, San Jose]
[David, Santa Clara]
[Lisa, Bangalore]
[Jack, New Delhi]
May 26, 2014 6:53:32 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
INFO: HHH000030: Cleaning up connection pool [jdbc:mysql://localhost/TestDB]

Поскольку я использую пример проекта HQL, вам нужно будет импортировать его, а затем добавить этот класс, чтобы он работал. Обратите внимание на запросы гибернации, выполняемые в выходных данных, таким образом вы можете уточнить свои запросы и получить нужные результаты. Это все, что нужно для быстрого обзора Criteria в Hibernate.