최대 절전 모드 기준 예제 자습서
Hibernate Criteria 예제 자습서에 오신 것을 환영합니다. 오늘 우리는 Hibernate의 Criteria를 살펴볼 것입니다.
최대 절전 모드 기준
- Hibernate Criteria API는 sum(), min(), max() 등과 같은 집계 함수에 사용할 수 있는 Projection을 제공합니다.
- Hibernate Criteria API는
ProjectionList와 함께 사용하여 선택한 열만 가져올 수 있습니다. - Hibernate의 기준은 여러 테이블을 조인하여 조인 쿼리에 사용할 수 있으며 Hibernate 기준 조인에 유용한 메소드는 createAlias(), setFetchMode() 및 setProjection()입니다.
- Hibernate API의 기준은 조건이 있는 결과를 가져오는 데 사용할 수 있으며 유용한 메서드는 제한을 추가할 수 있는 add()입니다.
- Hibernate Criteria API는 결과를 정렬하는 데 사용할 수 있는 addOrder() 메서드를 제공합니다.
아래 클래스는 Hibernate Criteria API의 다양한 사용법을 보여주며, 이들 중 대부분은 HQL 자습서의 예제를 대체합니다.
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();
}
}
위의 Hibernate Criteria 예제 프로그램을 실행하면 다음과 같은 출력을 얻습니다.
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]
저는 HQL 예제 프로젝트를 사용하고 있으므로 이를 가져오기한 다음 이 클래스를 추가해야 작동합니다. 출력에서 실행되는 최대 절전 모드 쿼리를 확인하십시오. 이렇게 하면 쿼리를 세분화하고 원하는 결과를 얻을 수 있습니다. 이것이 Hibernate의 Criteria에 대한 빠른 정리를 위한 전부입니다.