Пример именованного запроса Hibernate — @NamedQuery

Добро пожаловать в учебник по примерам именованных запросов Hibernate. Мы увидели, как можно использовать Native SQL Query в Hibernate. Если запросов будет много, то они вызовут бардак в коде, потому что все запросы будут разбросаны по всему проекту. Вот почему Hibernate предоставляет именованный запрос, который мы можем определить централизованно и использовать в любом месте кода. Мы можем создавать именованные запросы как для HQL, так и для собственного SQL.

Спящий именованный запрос

XML-файл конфигурации гибернации

hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE hibernate-configuration SYSTEM "https://hibernate.sourceforge.net/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" />
		<mapping resource="named-queries.hbm.xml" />
	</session-factory>
</hibernate-configuration>

XML-файл именованного запроса Hibernate

У нас есть файл отображения гибернации, который содержит только именованные запросы HQL и именованные запросы Native SQL. named-queries.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"https://hibernate.org/dtd/hibernate-mapping-3.0.dtd">
	
<hibernate-mapping>
	<query name="HQL_GET_ALL_EMPLOYEE">from Employee</query>

	<query name="HQL_GET_EMPLOYEE_BY_ID">
		<![CDATA[from Employee where emp_id = :id]]>
	</query>

	<query name="HQL_GET_EMPLOYEE_BY_SALARY">
		<![CDATA[from Employee where emp_salary > :salary]]>
	</query>
	
	<sql-query name="SQL_GET_ALL_EMPLOYEE">
		<![CDATA[select emp_id, emp_name, emp_salary from Employee]]>
	</sql-query>
	
	<sql-query name="SQL_GET_ALL_EMP_ADDRESS">
		<![CDATA[select {e.*}, {a.*} from Employee e join Address a ON e.emp_id=a.emp_id]]>
		<return alias="e" class="com.journaldev.hibernate.model.Employee" />
		<return-join alias="a" property="e.address"></return-join>
	</sql-query>
</hibernate-mapping>

элемент запроса используется для именованных запросов HQL, а элемент sql-query используется для собственных именованных запросов sql. Мы можем использовать возвращаемый элемент для объявления сущности, с которой будет сопоставлен набор результатов. return-join используется, когда у нас есть объединение нескольких таблиц. Мы должны использовать CDATA, чтобы объявить наш именованный запрос в режиме гибернации, чтобы убедиться, что он обрабатывается как данные, иначе символы < и > испортят наш XML-файл сопоставления.

Hibernate Named Query @NamedQuery Аннотация

У нас есть два модельных класса — Employee и Address. Мы определили запросы имен в классе Address, как показано ниже.

package com.journaldev.hibernate.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.NamedNativeQueries;
import javax.persistence.NamedNativeQuery;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
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")
@NamedQueries({ @NamedQuery(name = "@HQL_GET_ALL_ADDRESS", 
			query = "from Address") })
@NamedNativeQueries({ @NamedNativeQuery(name = "@SQL_GET_ALL_ADDRESS", 
			query = "select emp_id, address_line1, city, zipcode from 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;
	}

	@Override
	public String toString() {
		return "AddressLine1= " + addressLine1 + ", City=" + city
				+ ", Zipcode=" + zipcode;
	}
}

Программа тестирования именованных запросов Hibernate

Давайте напишем тестовую программу для использования всех именованных запросов hibernate, определенных выше.

package com.journaldev.hibernate.main;

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

public class HibernateNamedQueryExample {

	@SuppressWarnings("unchecked")
	public static void main(String[] args) {

		// Prep work
		SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
		Session session = sessionFactory.getCurrentSession();
		Transaction tx = session.beginTransaction();

		//HQL Named Query Example
		Query query = session.getNamedQuery("HQL_GET_ALL_EMPLOYEE");
		List<Employee> empList = query.list();
		for (Employee emp : empList) {
			System.out.println("List of Employees::" + emp.getId() + ","
					+ emp.getAddress().getCity());
		}

		query = session.getNamedQuery("HQL_GET_EMPLOYEE_BY_ID");
		query.setInteger("id", 2);
		Employee emp = (Employee) query.uniqueResult();
		System.out.println("Employee Name=" + emp.getName() + ", City="
				+ emp.getAddress().getCity());

		query = session.getNamedQuery("HQL_GET_EMPLOYEE_BY_SALARY");
		query.setInteger("salary", 200);
		empList = query.list();
		for (Employee emp1 : empList) {
			System.out.println("List of Employees::" + emp1.getId() + ","
					+ emp1.getSalary());
		}

		query = session.getNamedQuery("@HQL_GET_ALL_ADDRESS");
		List<Address> addressList = query.list();
		for (Address addr : addressList) {
			System.out.println("List of Address::" + addr.getId() + "::"
					+ addr.getZipcode() + "::" + addr.getEmployee().getName());
		}
		
		//Native SQL Named Query Example
		query = session.getNamedQuery("@SQL_GET_ALL_ADDRESS");
		List<Object[]> addressObjArray = query.list();
		for(Object[] row : addressObjArray){
			for(Object obj : row){
				System.out.print(obj + "::");
			}
			System.out.println("\n");
		}
		
		query = session.getNamedQuery("SQL_GET_ALL_EMP_ADDRESS");
		addressObjArray = query.list();
		for(Object[] row : addressObjArray){
			Employee e = (Employee) row[0];
			System.out.println("Employee Info::"+e);
			Address a = (Address) row[1];
			System.out.println("Address Info::"+a);
		}
		// rolling back to save the test data
		tx.commit();

		// closing hibernate resources
		sessionFactory.close();
	}

}

Когда мы выполняем вышеуказанную программу с имеющимися у нас тестовыми данными, она выводит следующий результат.

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 emp_id=?
Employee Name=David, City=Santa Clara
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 emp_salary>?
List of Employees::3,300.0
List of Employees::4,400.0
Hibernate: select address0_.emp_id as emp_id1_0_, address0_.address_line1 as address_2_0_, address0_.city as city3_0_, address0_.zipcode as zipcode4_0_ from ADDRESS address0_
List of Address::1::95129::Pankaj
List of Address::2::95051::David
List of Address::3::560100::Lisa
List of Address::4::100100::Jack
Hibernate: select emp_id, address_line1, city, zipcode from Address
1::Albany Dr::San Jose::95129::

2::Arques Ave::Santa Clara::95051::

3::BTM 1st Stage::Bangalore::560100::

4::City Centre::New Delhi::100100::

Hibernate: select e.emp_id as emp_id1_1_0_, e.emp_name as emp_name2_1_0_, e.emp_salary as emp_sala3_1_0_, a.emp_id as emp_id1_0_1_, a.address_line1 as address_2_0_1_, a.city as city3_0_1_, a.zipcode as zipcode4_0_1_ from Employee e join Address a ON e.emp_id=a.emp_id
Employee Info::Id= 1, Name= Pankaj, Salary= 100.0, {Address= AddressLine1= Albany Dr, City=San Jose, Zipcode=95129}
Address Info::AddressLine1= Albany Dr, City=San Jose, Zipcode=95129
Employee Info::Id= 2, Name= David, Salary= 200.0, {Address= AddressLine1= Arques Ave, City=Santa Clara, Zipcode=95051}
Address Info::AddressLine1= Arques Ave, City=Santa Clara, Zipcode=95051
Employee Info::Id= 3, Name= Lisa, Salary= 300.0, {Address= AddressLine1= BTM 1st Stage, City=Bangalore, Zipcode=560100}
Address Info::AddressLine1= BTM 1st Stage, City=Bangalore, Zipcode=560100
Employee Info::Id= 4, Name= Jack, Salary= 400.0, {Address= AddressLine1= City Centre, City=New Delhi, Zipcode=100100}
Address Info::AddressLine1= City Centre, City=New Delhi, Zipcode=100100

Hibernate Named Query Важные моменты

Несколько важных моментов в Hibernate Named Query:

1. Hibernate Named Query помогает нам группировать запросы в одном месте, а не разбрасывать их по всему коду.
2. Синтаксис именованного запроса гибернации проверяется при создании фабрики сеансов гибернации, что ускоряет сбой приложения в случае любой ошибки в именованных запросах.
3. Hibernate Named Query является глобальным. Это означает, что после определения его можно использовать во всем приложении.
4. Одним из основных недостатков именованного запроса является то, что его сложно отлаживать, поскольку нам нужно выяснить, где он определен.

Это все, что касается примера именованного запроса Hibernate, вы можете скачать пример проекта по ссылке ниже.

Скачать проект именованного запроса Hibernate