لغة استعلامات هايبرنيت – Hibernate Query Language – مثال تعليمي

الدروس التعليمية
Hibernate

HQL أو Hibernate Query Language هو لغة الاستعلام الشيئية لإطار Hibernate. HQL تشبه إلى حد كبير SQL باستثناء أننا نستخدم الكائنات بدلاً من أسماء الجداول، مما يجعلها أكثر قربًا من برمجة الكائنات.

لغة استعلام Hibernate – HQL

HQL وحساسية الحالة: HQL غير حساسة لحالة الأحرف باستثناء أسماء فئة ومتغيرات Java. لذلك، SeLeCT هو نفسه كـ sELEct هو نفسه كـ SELECT، ولكن com.journaldev.model.Employee ليست نفسها كـ com.journaldev.model.EMPLOYEE. بعض العبارات المدعومة بشكل شائع في HQL هي:

  1. HQL From: HQL From هو نفسه كـ عبارة select في SQL، from Employee هو نفسه كـ select * from Employee. يمكننا أيضًا إنشاء اختصار مثل from Employee emp أو from Employee as emp.
  2. HQL Join : HQL تدعم الانضمام الداخلي، الانضمام الخارجي الأيسر، الانضمام الخارجي الأيمن، والانضمام الكامل. على سبيل المثال، select e.name, a.city from Employee e INNER JOIN e.address a. في هذا الاستعلام، يجب أن يحتوي فئة Employee على متغير يسمى address. سنتناول ذلك في كود المثال.
  3. وظائف التجميع: تدعم HQL الوظائف التجميعية المستخدمة بشكل شائع مثل count(*)، count(distinct x)، min()، max()، avg() و sum().
  4. التعابير: تدعم HQL التعابير الحسابية (+، -، *، /)، وعوامل المقارنة الثنائية (=، >=، <=، <>, !=، like)، والعمليات المنطقية (and، or، not) وغيرها.
  5. تدعم HQL أيضًا عبارات ordre by و group by.
  6. تدعم HQL أيضًا الاستعلامات الفرعية تمامًا مثل استعلامات SQL.
  7. تدعم HQL DDL، DML وتنفيذ إجراءات التخزين أيضًا.

لنلقِ نظرة على مثال بسيط على استخدام HQL في برنامجنا.

مثال HQL لإعداد قاعدة بيانات

I am using MySQL database for my example, below script will create two tables Employee and Address. They have one-to-one mapping and I am inserting some demo data for my example.

CREATE TABLE `Employee` (
  `emp_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `emp_name` varchar(20) NOT NULL,
  `emp_salary` double(10,0) NOT NULL DEFAULT '0',
  PRIMARY KEY (`emp_id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
 
CREATE TABLE `Address` (
  `emp_id` int(11) unsigned NOT NULL,
  `address_line1` varchar(50) NOT NULL DEFAULT '',
  `zipcode` varchar(10) DEFAULT NULL,
  `city` varchar(20) DEFAULT NULL,
  PRIMARY KEY (`emp_id`),
  CONSTRAINT `emp_fk_1` FOREIGN KEY (`emp_id`) REFERENCES `Employee` (`emp_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `Employee` (`emp_id`, `emp_name`, `emp_salary`)
VALUES
	(1, 'Pankaj', 100),
	(2, 'David', 200),
	(3, 'Lisa', 300),
	(4, 'Jack', 400);


INSERT INTO `Address` (`emp_id`, `address_line1`, `zipcode`, `city`)
VALUES
	(1, 'Albany Dr', '95129', 'San Jose'),
	(2, 'Arques Ave', '95051', 'Santa Clara'),
	(3, 'BTM 1st Stage', '560100', 'Bangalore'),
	(4, 'City Centre', '100100', 'New Delhi');
	
commit;

قم بإنشاء مشروع Maven في Eclipse أو البيئة المتكاملة التي تستخدمها، سيبدو مشروعنا النهائي مثل الصورة أدناه.

تبعيات Hibernate Maven

ملف pom.xml النهائي يحتوي على تبعيات Hibernate ومشغل MySQL.

<project xmlns="https://maven.apache.org/POM/4.0.0" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.journaldev.hibernate</groupId>
  <artifactId>HQLExample</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <dependencies>
  	<dependency>
  		<groupId>org.hibernate</groupId>
  		<artifactId>hibernate-core</artifactId>
  		<version>4.3.5.Final</version>
  	</dependency>
  	<dependency>
  		<groupId>mysql</groupId>
  		<artifactId>mysql-connector-java</artifactId>
  		<version>5.0.5</version>
  	</dependency>
  </dependencies>
</project>

تكوين Hibernate XML

يحتوي ملف تكوين Hibernate XML الخاص بنا على خصائص ذات صلة باتصال قاعدة البيانات وفئات التعيين. سأستخدم التعليقات لتعيين Hibernate. الشيفرة hibernate.cfg.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
		"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
		"https://hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.password">pankaj123</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost/TestDB</property>
        <property name="hibernate.connection.username">pankaj</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        
        <property name="hibernate.current_session_context_class">thread</property>
        <property name="hibernate.show_sql">true</property>
        
        <mapping class="com.journaldev.hibernate.model.Employee"/>
        <mapping class="com.journaldev.hibernate.model.Address"/>
    </session-factory>
</hibernate-configuration>

فئة الأداة لمصنع الجلسة Hibernate

لدينا فئة أداة لتكوين مصنع جلسة Hibernate.

package com.journaldev.hibernate.util;

import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;

public class HibernateUtil {

	private static SessionFactory sessionFactory;
	
	private static SessionFactory buildSessionFactory() {
        try {
            // إنشاء مصنع الجلسة من hibernate.cfg.xml
        	Configuration configuration = new Configuration();
        	configuration.configure("hibernate.cfg.xml");
        	System.out.println("Hibernate Configuration loaded");
        	
        	ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
        	System.out.println("Hibernate serviceRegistry created");
        	
        	SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        	
            return sessionFactory;
        }
        catch (Throwable ex) {
            System.err.println("Initial SessionFactory creation failed." + ex);
            ex.printStackTrace();
            throw new ExceptionInInitializerError(ex);
        }
    }
	
	public static SessionFactory getSessionFactory() {
		if(sessionFactory == null) sessionFactory = buildSessionFactory();
        return sessionFactory;
    }
}

فئات النموذج مع تعيينات مبنية على التعليقات

تبدو فئات النموذج الخاصة بنا مع تعليقات JPA كما يلي.

package com.journaldev.hibernate.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;

import org.hibernate.annotations.Cascade;

@Entity
@Table(name = "EMPLOYEE")
public class Employee {

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Column(name = "emp_id")
	private long id;

	@Column(name = "emp_name")
	private String name;

	@Column(name = "emp_salary")
	private double salary;

	@OneToOne(mappedBy = "employee")
	@Cascade(value = org.hibernate.annotations.CascadeType.ALL)
	private Address address;

	public long getId() {
		return id;
	}

	public void setId(long id) {
		this.id = id;
	}

	public Address getAddress() {
		return address;
	}

	public void setAddress(Address address) {
		this.address = address;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public double getSalary() {
		return salary;
	}

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

}

package com.journaldev.hibernate.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;

import org.hibernate.annotations.GenericGenerator;
import org.hibernate.annotations.Parameter;

@Entity
@Table(name = "ADDRESS")
public class Address {

	@Id
	@Column(name = "emp_id", unique = true, nullable = false)
	@GeneratedValue(generator = "gen")
	@GenericGenerator(name = "gen", strategy = "foreign", 
				parameters = { @Parameter(name = "property", value = "employee") })
	private long id;

	@Column(name = "address_line1")
	private String addressLine1;

	@Column(name = "zipcode")
	private String zipcode;

	@Column(name = "city")
	private String city;

	@OneToOne
	@PrimaryKeyJoinColumn
	private Employee employee;

	public long getId() {
		return id;
	}

	public void setId(long id) {
		this.id = id;
	}

	public String getAddressLine1() {
		return addressLine1;
	}

	public void setAddressLine1(String addressLine1) {
		this.addressLine1 = addressLine1;
	}

	public String getZipcode() {
		return zipcode;
	}

	public void setZipcode(String zipcode) {
		this.zipcode = zipcode;
	}

	public String getCity() {
		return city;
	}

	public void setCity(String city) {
		this.city = city;
	}

	public Employee getEmployee() {
		return employee;
	}

	public void setEmployee(Employee employee) {
		this.employee = employee;
	}

}

فئة اختبار مثال HQL

لنرى كيفية استخدام HQL في برامج Java.

package com.journaldev.hibernate.main;

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

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;

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

public class HQLExamples {

	@SuppressWarnings("unchecked")
	public static void main(String[] args) {
		
		//التحضير
		SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
		Session session = sessionFactory.getCurrentSession();
		
		//مثال HQL - الحصول على جميع الموظفين
		Transaction tx = session.beginTransaction();
		Query query = session.createQuery("from Employee");
		List empList = query.list();
		for(Employee emp : empList){
			System.out.println("List of Employees::"+emp.getId()+","+emp.getAddress().getCity());
		}
		
		//مثال HQL - الحصول على موظف بمعرف
		query = session.createQuery("from Employee where id= :id");
		query.setLong("id", 3);
		Employee emp = (Employee) query.uniqueResult();
		System.out.println("Employee Name="+emp.getName()+", City="+emp.getAddress().getCity());
		
		//مثال HQL لتقسيم الصفحات
		query = session.createQuery("from Employee");
		query.setFirstResult(0); //starts with 0
		query.setFetchSize(2);
		empList = query.list();
		for(Employee emp4 : empList){
			System.out.println("Paginated Employees::"+emp4.getId()+","+emp4.getAddress().getCity());
		}
		
		//تحديث HQL للموظف
		query = session.createQuery("update Employee set name= :name where id= :id");
		query.setParameter("name", "Pankaj Kumar");
		query.setLong("id", 1);
		int result = query.executeUpdate();
		System.out.println("Employee Update Status="+result);

		//حذف موظف HQL، نحتاج إلى الاهتمام بالقيود المفتاحية الخارجية أيضًا
		query = session.createQuery("delete from Address where id= :id");
		query.setLong("id", 4);
		result = query.executeUpdate();
		System.out.println("Address Delete Status="+result);
		
		query = session.createQuery("delete from Employee where id= :id");
		query.setLong("id", 4);
		result = query.executeUpdate();
		System.out.println("Employee Delete Status="+result);
		
		//أمثلة وظيفة الجمع في HQL
		query = session.createQuery("select sum(salary) from Employee");
		double sumSalary = (Double) query.uniqueResult();
		System.out.println("Sum of all Salaries= "+sumSalary);
		
		//أمثلة الانضمام HQL
		query = session.createQuery("select e.name, a.city from Employee e "
				+ "INNER JOIN e.address a");
		List list = query.list();
		for(Object[] arr : list){
			System.out.println(Arrays.toString(arr));
		}
		
		//مثال على التجميع والمجموعة حسب في HQL
		query = session.createQuery("select e.name, sum(e.salary), count(e)"
				+ " from Employee e where e.name like '%i%' group by e.name");
		List groupList = query.list();
		for(Object[] arr : groupList){
			System.out.println(Arrays.toString(arr));
		}
		
		//مثال على ترتيب حسب HQL
		query = session.createQuery("from Employee e order by e.id desc");
		empList = query.list();
		for(Employee emp3 : empList){
			System.out.println("ID Desc Order Employee::"+emp3.getId()+","+emp3.getAddress().getCity());
		}
		
		//العودة للوراء لحفظ بيانات الاختبار
		tx.rollback();
		
		//إغلاق موارد الهايبرنيت
		sessionFactory.close();
	}

}

لاحظ أنني استخدم HQL لعمليات الاختيار والتحديث والحذف. كما يوضح كيفية استخدام الانضمام ووظائف الجمع في HQL. عند تشغيل برنامج مثال HQL أعلاه، نحصل على النتائج التالية.

May 22, 2014 1:55:37 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit>
INFO: HCANN000001: Hibernate Commons Annotations {4.0.4.Final}
May 22, 2014 1:55:37 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {4.3.5.Final}
May 22, 2014 1:55:37 PM org.hibernate.cfg.Environment <clinit>
INFO: HHH000206: hibernate.properties not found
May 22, 2014 1:55:37 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
May 22, 2014 1:55:37 PM org.hibernate.cfg.Configuration configure
INFO: HHH000043: Configuring from resource: hibernate.cfg.xml
May 22, 2014 1:55:37 PM org.hibernate.cfg.Configuration getConfigurationInputStream
INFO: HHH000040: Configuration resource: hibernate.cfg.xml
May 22, 2014 1:55:37 PM org.hibernate.cfg.Configuration doConfigure
INFO: HHH000041: Configured SessionFactory: null
Hibernate Configuration loaded
Hibernate serviceRegistry created
May 22, 2014 1:55:37 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH000402: Using Hibernate built-in connection pool (not for production use!)
May 22, 2014 1:55:37 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH000401: using driver [com.mysql.jdbc.Driver] at URL [jdbc:mysql://localhost/TestDB]
May 22, 2014 1:55:37 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH000046: Connection properties: {user=pankaj, password=****}
May 22, 2014 1:55:37 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH000006: Autocommit mode: false
May 22, 2014 1:55:37 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
May 22, 2014 1:55:37 PM org.hibernate.dialect.Dialect <init>
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect
May 22, 2014 1:55:37 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 22, 2014 1:55:38 PM org.hibernate.engine.transaction.internal.TransactionFactoryInitiator initiateService
INFO: HHH000399: Using default transaction strategy (direct JDBC transactions)
May 22, 2014 1:55:38 PM org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory <init>
INFO: HHH000397: Using ASTQueryTranslatorFactory
Hibernate: select employee0_.emp_id as emp_id1_1_, employee0_.emp_name as emp_name2_1_, employee0_.emp_salary as emp_sala3_1_ from EMPLOYEE employee0_
Hibernate: select address0_.emp_id as emp_id1_0_0_, address0_.address_line1 as address_2_0_0_, address0_.city as city3_0_0_, address0_.zipcode as zipcode4_0_0_, employee1_.emp_id as emp_id1_1_1_, employee1_.emp_name as emp_name2_1_1_, employee1_.emp_salary as emp_sala3_1_1_ from ADDRESS address0_ left outer join EMPLOYEE employee1_ on address0_.emp_id=employee1_.emp_id where address0_.emp_id=?
Hibernate: select address0_.emp_id as emp_id1_0_0_, address0_.address_line1 as address_2_0_0_, address0_.city as city3_0_0_, address0_.zipcode as zipcode4_0_0_, employee1_.emp_id as emp_id1_1_1_, employee1_.emp_name as emp_name2_1_1_, employee1_.emp_salary as emp_sala3_1_1_ from ADDRESS address0_ left outer join EMPLOYEE employee1_ on address0_.emp_id=employee1_.emp_id where address0_.emp_id=?
Hibernate: select address0_.emp_id as emp_id1_0_0_, address0_.address_line1 as address_2_0_0_, address0_.city as city3_0_0_, address0_.zipcode as zipcode4_0_0_, employee1_.emp_id as emp_id1_1_1_, employee1_.emp_name as emp_name2_1_1_, employee1_.emp_salary as emp_sala3_1_1_ from ADDRESS address0_ left outer join EMPLOYEE employee1_ on address0_.emp_id=employee1_.emp_id where address0_.emp_id=?
Hibernate: select address0_.emp_id as emp_id1_0_0_, address0_.address_line1 as address_2_0_0_, address0_.city as city3_0_0_, address0_.zipcode as zipcode4_0_0_, employee1_.emp_id as emp_id1_1_1_, employee1_.emp_name as emp_name2_1_1_, employee1_.emp_salary as emp_sala3_1_1_ from ADDRESS address0_ left outer join EMPLOYEE employee1_ on address0_.emp_id=employee1_.emp_id where address0_.emp_id=?
List of Employees::1,San Jose
List of Employees::2,Santa Clara
List of Employees::3,Bangalore
List of Employees::4,New Delhi
Hibernate: select employee0_.emp_id as emp_id1_1_, employee0_.emp_name as emp_name2_1_, employee0_.emp_salary as emp_sala3_1_ from EMPLOYEE employee0_ where employee0_.emp_id=?
Employee Name=Lisa, City=Bangalore
Hibernate: select employee0_.emp_id as emp_id1_1_, employee0_.emp_name as emp_name2_1_, employee0_.emp_salary as emp_sala3_1_ from EMPLOYEE employee0_
Paginated Employees::1,San Jose
Paginated Employees::2,Santa Clara
Paginated Employees::3,Bangalore
Paginated Employees::4,New Delhi
Hibernate: update EMPLOYEE set emp_name=? where emp_id=?
Employee Update Status=1
Hibernate: delete from ADDRESS where emp_id=?
Address Delete Status=1
Hibernate: delete from EMPLOYEE where emp_id=?
Employee Delete Status=1
Hibernate: select sum(employee0_.emp_salary) as col_0_0_ from EMPLOYEE employee0_
Sum of all Salaries= 600.0
Hibernate: select employee0_.emp_name as col_0_0_, address1_.city as col_1_0_ from EMPLOYEE employee0_ inner join ADDRESS address1_ on employee0_.emp_id=address1_.emp_id
[Pankaj Kumar, San Jose]
[David, Santa Clara]
[Lisa, Bangalore]
Hibernate: select employee0_.emp_name as col_0_0_, sum(employee0_.emp_salary) as col_1_0_, count(employee0_.emp_id) as col_2_0_ from EMPLOYEE employee0_ where employee0_.emp_name like '%i%' group by employee0_.emp_name
[David, 200.0, 1]
[Lisa, 300.0, 1]
Hibernate: select employee0_.emp_id as emp_id1_1_, employee0_.emp_name as emp_name2_1_, employee0_.emp_salary as emp_sala3_1_ from EMPLOYEE employee0_ order by employee0_.emp_id desc
ID Desc Order Employee::3,Bangalore
ID Desc Order Employee::2,Santa Clara
ID Desc Order Employee::1,San Jose
May 22, 2014 1:55:38 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
INFO: HHH000030: Cleaning up connection pool [jdbc:mysql://localhost/TestDB]

لاحظ أنه بمجرد أن يتم تنفيذ عملية الحذف، لا تظهر العمليات اللاحقة البيانات الخاصة بهذا السجل (مجموع الراتب 600). ومع ذلك، أنا أقوم بالتراجع عن العملية، لذا البيانات في الجدول ستبقى دون تغيير. قم بتغيير الكود لتأكيد العملية وسيتم عكسها في جداول قاعدة البيانات. لا أحب استخدام استعلام HQL كثيرًا لأنه كما يمكنك رؤية أنه يجب أن نأخذ عناية بتعيينات الجدول في كودنا. إذا استخدمنا الجلسة لحذف كائن الموظف، فسيقوم بحذف السجل من كل من الجداول. يمكنك تنزيل مشروع المثال على HQL من الرابط أدناه وتجربة المزيد من الأمثلة.

تحميل مشروع Hibernate HQL

Source:
https://www.digitalocean.com/community/tutorials/hibernate-query-language-hql-example-tutorial