HQL - Hibernate 쿼리 언어 - 예제 자습서
HQL 또는 Hibernate Query Language는 Hibernate Framework의 객체 지향 쿼리 언어입니다. HQL은 테이블 이름 대신 개체를 사용한다는 점을 제외하면 SQL과 매우 유사하여 개체 지향 프로그래밍에 더 가깝습니다.
Hibernate 쿼리 언어 - HQL
- HQL From: HQL From은 SQL의 select 절과 같고,
from Employee는select * from Employee와 같습니다.from Employee emp또는from Employee as emp와 같은 별칭을 만들 수도 있습니다. - HQL 조인: HQL은 내부 조인, 왼쪽 외부 조인, 오른쪽 외부 조인 및 전체 조인을 지원합니다. 예를 들어
Employee e INNER JOIN e.address a에서 e.name, a.city를 선택합니다. 이 쿼리에서 Employee 클래스에는 주소라는 변수가 있어야 합니다. 예제 코드에서 살펴보겠습니다. - 집계 함수: HQL은 count(*), count(distinct x), min(), max(), avg() 및 sum()과 같이 일반적으로 사용되는 집계 함수를 지원합니다.
- 표현식: HQL은 산술식(+, -, *, /), 이진 비교 연산자(=, >=, <=, <>, !=, like), 논리 연산(and, or, not) 등을 지원합니다. .
- HQL은 또한 ordre by 및 group by 절을 지원합니다.
- HQL은 SQL 쿼리와 마찬가지로 하위 쿼리도 지원합니다.
- HQL은 DDL, DML 및 스토어 프로시저 실행도 지원합니다.
프로그램에서 HQL을 사용하는 간단한 예를 살펴보겠습니다.
HQL 예제 데이터베이스 설정
예를 들어 MySQL 데이터베이스를 사용하고 있습니다. 아래 스크립트는 Employee 및 Address라는 두 개의 테이블을 만듭니다. 그들은 일대일 매핑을 가지고 있으며 제 예제에 대한 데모 데이터를 삽입하고 있습니다.
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;
Hibernate Maven 종속성
최종 pom.xml에는 Hibernate 및 MySQL 드라이버에 대한 종속성이 포함되어 있습니다.
<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>
Hibernate 구성 XML
Hibernate 구성 xml 파일에는 데이터베이스 연결 관련 속성 및 매핑 클래스가 포함되어 있습니다. Hibernate 매핑을 위해 주석을 사용할 것입니다. hibernate.cfg.xml 코드:
<?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>
Hibernate SessionFactory 유틸리티 클래스
최대 절전 모드 SessionFactory를 구성하는 유틸리티 클래스가 있습니다.
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 {
// Create the SessionFactory from 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;
}
}
주석 기반 매핑이 있는 모델 클래스
JPA 주석이 있는 모델 클래스는 아래와 같습니다.
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;
}
}
HQL 예제 테스트 클래스
자바 프로그램에서 HQL을 어떻게 사용하는지 알아보자.
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) {
//Prep work
SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
Session session = sessionFactory.getCurrentSession();
//HQL example - Get All Employees
Transaction tx = session.beginTransaction();
Query query = session.createQuery("from Employee");
List<Employee> empList = query.list();
for(Employee emp : empList){
System.out.println("List of Employees::"+emp.getId()+","+emp.getAddress().getCity());
}
//HQL example - Get Employee with id
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());
//HQL pagination example
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());
}
//HQL Update Employee
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);
//HQL Delete Employee, we need to take care of foreign key constraints too
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);
//HQL Aggregate function examples
query = session.createQuery("select sum(salary) from Employee");
double sumSalary = (Double) query.uniqueResult();
System.out.println("Sum of all Salaries= "+sumSalary);
//HQL join examples
query = session.createQuery("select e.name, a.city from Employee e "
+ "INNER JOIN e.address a");
List<Object[]> list = query.list();
for(Object[] arr : list){
System.out.println(Arrays.toString(arr));
}
//HQL group by and like example
query = session.createQuery("select e.name, sum(e.salary), count(e)"
+ " from Employee e where e.name like '%i%' group by e.name");
List<Object[]> groupList = query.list();
for(Object[] arr : groupList){
System.out.println(Arrays.toString(arr));
}
//HQL order by example
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());
}
//rolling back to save the test data
tx.rollback();
//closing hibernate resources
sessionFactory.close();
}
}
선택, 업데이트 및 삭제 작업에 HQL을 사용하고 있습니다. 또한 HQL Join 및 HQL Aggregate 기능을 사용하는 방법도 보여줍니다. 위의 hql 예제 프로그램을 실행하면 다음과 같은 결과가 나타납니다.
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]
삭제 작업이 수행되면 추가 작업에서 해당 레코드 데이터(급여 합계는 600)가 표시되지 않습니다. 그러나 트랜잭션을 롤백하므로 테이블의 데이터는 변경되지 않습니다. 트랜잭션을 커밋하도록 코드를 변경하면 데이터베이스 테이블에 반영됩니다. 보시다시피 코드에서 테이블 매핑을 처리해야 하기 때문에 HQL 쿼리를 많이 사용하는 것을 좋아하지 않습니다. Session을 사용하여 Employee 개체를 삭제하면 두 테이블 모두에서 레코드가 삭제됩니다. 아래 링크에서 샘플 hql 예제 프로젝트를 다운로드하고 더 많은 예제를 시도해 볼 수 있습니다.
Hibernate HQL 프로젝트 다운로드