Наиболее распрастранённым типом ассоциации является тип Many-to-One при котором один объект может быть ассоциирован с несколькими другими объектами. Например мы можем ассоциировать несколько разработчиков с одной компанией, в которой они работают.
Для понимания того, как это работает на практике рассмотрим пример простого приложения.
Пример:
Исходный код проекта можно скачать по ЭТОЙ ССЫЛКЕ.
Шаг 1. Создадим две таблицы в нашей базе данных (далее – БД)
HIBERNATE_DEVELOPERS
CREATE TABLE HIBERNATE_DEVELOPERS(
ID INT NOT NULL AUTO_INCREMENT,
FIRST_NAME VARCHAR(50) DEFAULT NULL,
LAST_NAME VARCHAR(50) DEFAULT NULL,
SPECIALTY VARCHAR(50) DEFAULT NULL,
EXPERIENCE INT DEFAULT NULL,
COMPANY INT NOT NULL,
PRIMARY KEY(ID)
);
HIBERNATE_COMPANIES
CREATE TABLE HIBERNATE_COMPANIES (
id INT NOT NULL auto_increment,
COMPANY_NAME VARCHAR(100) default NULL,
PRIMARY KEY (id)
);
Шаг 2. Создадим POJO – классы
Developer.java
package net.proselyte.hibernate.association.manytoone;
public class Developer {
private int id;
private String firstName;
private String lastName;
private String specialty;
private int experience;
private Company company;
/**
* Default Constructor
*/
public Developer() {
}
/**
* Plain constructor
*/
public Developer(String firstName, String lastName, String specialty, int experience, Company company) {
this.firstName = firstName;
this.lastName = lastName;
this.specialty = specialty;
this.experience = experience;
this.company = company;
}
/**
* Getters and Setters
*/
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getSpecialty() {
return specialty;
}
public void setSpecialty(String specialty) {
this.specialty = specialty;
}
public int getExperience() {
return experience;
}
public void setExperience(int experience) {
this.experience = experience;
}
public Company getCompany() {
return company;
}
public void setCompany(Company company) {
this.company = company;
}
/**
* toString method (optional)
*/
@Override
public String toString() {
return "Developer:\n" +
"id: " + id +
"\nFirst Name: " + firstName + "\n" +
"Last Name: " + lastName + "\n" +
"Specialty: " + specialty + "\n" +
"Experience: " + experience + "\n" +
"Company: " + company;
}
}
Company.java
package net.proselyte.hibernate.association.manytoone;
public class Company {
private int id;
private String companyName;
public Company() {
}
public Company(String companyName) {
this.companyName = companyName;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getCompanyName() {
return companyName;
}
public void setCompanyName(String companyName) {
this.companyName = companyName;
}
@Override
public String toString() {
return "Company:" +
"\nCompany ID: " + id +
"\nCompany Name: " + companyName + "\n";
}
}
Шаг 3. Создадим конфигурационные файлы
hibernate.cfg.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration SYSTEM
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.dialect">
org.hibernate.dialect.MySQLDialect
</property>
<property name="hibernate.connection.driver_class">
com.mysql.jdbc.Driver
</property>
<!-- Assume PROSELYTE_TUTORIAL is the database name -->
<property name="hibernate.connection.url">
jdbc:mysql://localhost/ИМЯ_ВАШЕЙ_БД
</property>
<property name="hibernate.connection.username">
ВАШЕ_ИМЯ_ПОЛЬЗОВАТЕЛЯ
</property>
<property name="hibernate.connection.password">
ВАШ_ПАРОЛЬ
</property>
<!-- List of XML mapping files -->
<mapping resource="Developer.hbm.xml"/>
</session-factory>
</hibernate-configuration>
Developer.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="net.proselyte.hibernate.association.manytoone.Developer" table="HIBERNATE_DEVELOPERS">
<meta attribute="class-description">
This class contains developer's detail.
</meta>
<id name="id" type="int" column="id">
<generator class="native"/>
</id>
<property name="firstName" column="FIRST_NAME" type="string"/>
<property name="lastName" column="LAST_NAME" type="string"/>
<property name="specialty" column="SPECIALTY" type="string"/>
<property name="experience" column="EXPERIENCE" type="int"/>
<many-to-one name="company" column="COMPANY" not-null="true"
class="net.proselyte.hibernate.association.manytoone.Company"/>
</class>
<class name="net.proselyte.hibernate.association.manytoone.Company" table="HIBERNATE_COMPANIES">
<meta attribute="class-description">
This class contains company details.
</meta>
<id name="id" type="int" column="ID">
<generator class="native"/>
</id>
<property name="companyName" column="COMPANY_NAME" type="string"/>
</class>
</hibernate-mapping>
Шаг 4. Создадим класс DeveloperRunner.java
DeveloperRunner.java
package net.proselyte.hibernate.association.manytoone;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import java.util.List;
public class DeveloperRunner {
private static SessionFactory sessionFactory;
public static void main(String[] args) {
sessionFactory = new Configuration().configure().buildSessionFactory();
DeveloperRunner developerRunner = new DeveloperRunner();
System.out.println("Adding company record...");
Company company = developerRunner.addCompany("Proselyte.net");
System.out.println("Creating developer's records...");
Integer developerId1 = developerRunner.addDeveloper("Proselyte", "Developer", "Java Developer", 2, company);
Integer developerId2 = developerRunner.addDeveloper("Peter", "Programmer", "C++ Developer", 2, company);
System.out.println("List of Developers: ");
developerRunner.listDevelopers();
System.out.println("Updating experience of Proselyte to 3 years and removing Peter...");
developerRunner.updateDeveloper(developerId1, 3);
developerRunner.removeDeveloper(developerId2);
System.out.println("Final list of Developers: ");
developerRunner.listDevelopers();
sessionFactory.close();
}
public Integer addDeveloper(String firstName, String lastName, String specialty, int experience, Company company) {
Session session = sessionFactory.openSession();
Transaction transaction = null;
Integer developerId = null;
transaction = session.beginTransaction();
Developer developer = new Developer(firstName, lastName, specialty, experience, company);
developerId = (Integer) session.save(developer);
transaction.commit();
session.close();
return developerId;
}
public Company addCompany(String companyName) {
Session session = sessionFactory.openSession();
Transaction transaction = null;
Company company = null;
transaction = session.beginTransaction();
company = new Company(companyName);
session.save(company);
transaction.commit();
session.close();
return company;
}
public void listDevelopers() {
Session session = sessionFactory.openSession();
Transaction transaction = null;
transaction = session.beginTransaction();
List developers = session.createQuery("FROM Developer").list();
for (Developer developer : developers) {
System.out.println(developer);
System.out.println("\n================\n");
}
session.close();
}
public void updateDeveloper(int developerId, int experience) {
Session session = sessionFactory.openSession();
Transaction transaction = null;
transaction = session.beginTransaction();
Developer developer = (Developer) session.get(Developer.class, developerId);
developer.setExperience(experience);
session.update(developer);
transaction.commit();
session.close();
}
public void removeDeveloper(int developerId) {
Session session = sessionFactory.openSession();
Transaction transaction = null;
transaction = session.beginTransaction();
Developer developer = (Developer) session.get(Developer.class, developerId);
session.delete(developer);
transaction.commit();
session.close();
}
}
Если всё было сделано правильно, то в результате работы программы мы получим, примерно, следующий результат:
/usr/lib/jvm/java-8-oracle/bin/java -Didea.launcher.port=7537 -Didea.launcher.bin.path=/home/proselyte/Programming/Soft/IntellijIdea/bin -Dfile.encoding=UTF-8 -classpath /usr/lib/jvm/java-8-oracle/jre/lib/management-agent.jar:/usr/lib/jvm/java-8-oracle/jre/lib/plugin.jar:/usr/lib/jvm/java-8-oracle/jre/lib/rt.jar:/usr/lib/jvm/java-8-oracle/jre/lib/jsse.jar:/usr/lib/jvm/java-8-oracle/jre/lib/charsets.jar:/usr/lib/jvm/java-8-oracle/jre/lib/jce.jar:/usr/lib/jvm/java-8-oracle/jre/lib/resources.jar:/usr/lib/jvm/java-8-oracle/jre/lib/deploy.jar:/usr/lib/jvm/java-8-oracle/jre/lib/jfxswt.jar:/usr/lib/jvm/java-8-oracle/jre/lib/javaws.jar:/usr/lib/jvm/java-8-oracle/jre/lib/jfr.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/dnsns.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/sunpkcs11.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/sunec.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/sunjce_provider.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/jaccess.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/nashorn.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/localedata.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/zipfs.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/cldrdata.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/jfxrt.jar:/home/proselyte/Programming/IdeaProjects/ProselyteTutorials/Hibernate/target/classes:/home/proselyte/.m2/repository/org/springframework/spring-core/4.1.1.RELEASE/spring-core-4.1.1.RELEASE.jar:/home/proselyte/.m2/repository/commons-logging/commons-logging/1.1.3/commons-logging-1.1.3.jar:/home/proselyte/.m2/repository/org/springframework/spring-web/4.1.1.RELEASE/spring-web-4.1.1.RELEASE.jar:/home/proselyte/.m2/repository/org/springframework/spring-aop/4.1.1.RELEASE/spring-aop-4.1.1.RELEASE.jar:/home/proselyte/.m2/repository/aopalliance/aopalliance/1.0/aopalliance-1.0.jar:/home/proselyte/.m2/repository/org/springframework/spring-beans/4.1.1.RELEASE/spring-beans-4.1.1.RELEASE.jar:/home/proselyte/.m2/repository/org/springframework/spring-context/4.1.1.RELEASE/spring-context-4.1.1.RELEASE.jar:/home/proselyte/.m2/repository/javax/servlet/servlet-api/2.5/servlet-api-2.5.jar:/home/proselyte/.m2/repository/org/springframework/spring-webmvc/4.1.1.RELEASE/spring-webmvc-4.1.1.RELEASE.jar:/home/proselyte/.m2/repository/org/springframework/spring-expression/4.1.1.RELEASE/spring-expression-4.1.1.RELEASE.jar:/home/proselyte/.m2/repository/org/springframework/integration/spring-integration-file/4.2.1.RELEASE/spring-integration-file-4.2.1.RELEASE.jar:/home/proselyte/.m2/repository/org/springframework/integration/spring-integration-core/4.2.1.RELEASE/spring-integration-core-4.2.1.RELEASE.jar:/home/proselyte/.m2/repository/org/springframework/spring-messaging/4.2.2.RELEASE/spring-messaging-4.2.2.RELEASE.jar:/home/proselyte/.m2/repository/org/springframework/retry/spring-retry/1.1.2.RELEASE/spring-retry-1.1.2.RELEASE.jar:/home/proselyte/.m2/repository/org/springframework/spring-tx/4.2.2.RELEASE/spring-tx-4.2.2.RELEASE.jar:/home/proselyte/.m2/repository/commons-io/commons-io/2.4/commons-io-2.4.jar:/home/proselyte/.m2/repository/org/hibernate/hibernate-core/5.1.0.Final/hibernate-core-5.1.0.Final.jar:/home/proselyte/.m2/repository/org/jboss/logging/jboss-logging/3.3.0.Final/jboss-logging-3.3.0.Final.jar:/home/proselyte/.m2/repository/org/hibernate/javax/persistence/hibernate-jpa-2.1-api/1.0.0.Final/hibernate-jpa-2.1-api-1.0.0.Final.jar:/home/proselyte/.m2/repository/org/javassist/javassist/3.20.0-GA/javassist-3.20.0-GA.jar:/home/proselyte/.m2/repository/antlr/antlr/2.7.7/antlr-2.7.7.jar:/home/proselyte/.m2/repository/org/apache/geronimo/specs/geronimo-jta_1.1_spec/1.1.1/geronimo-jta_1.1_spec-1.1.1.jar:/home/proselyte/.m2/repository/org/jboss/jandex/2.0.0.Final/jandex-2.0.0.Final.jar:/home/proselyte/.m2/repository/com/fasterxml/classmate/1.3.0/classmate-1.3.0.jar:/home/proselyte/.m2/repository/dom4j/dom4j/1.6.1/dom4j-1.6.1.jar:/home/proselyte/.m2/repository/xml-apis/xml-apis/1.0.b2/xml-apis-1.0.b2.jar:/home/proselyte/.m2/repository/org/hibernate/common/hibernate-commons-annotations/5.0.1.Final/hibernate-commons-annotations-5.0.1.Final.jar:/home/proselyte/.m2/repository/javassist/javassist/3.12.1.GA/javassist-3.12.1.GA.jar:/home/proselyte/.m2/repository/mysql/mysql-connector-java/5.1.38/mysql-connector-java-5.1.38.jar:/home/proselyte/Programming/Soft/IntellijIdea/lib/idea_rt.jar com.intellij.rt.execution.application.AppMain net.proselyte.hibernate.association.manytoone.DeveloperRunner
Feb 22, 2016 11:54:37 AM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {5.1.0.Final}
Feb 22, 2016 11:54:37 AM org.hibernate.cfg.Environment
INFO: HHH000206: hibernate.properties not found
Feb 22, 2016 11:54:37 AM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
Feb 22, 2016 11:54:37 AM org.hibernate.annotations.common.reflection.java.JavaReflectionManager
INFO: HCANN000001: Hibernate Commons Annotations {5.0.1.Final}
Feb 22, 2016 11:54:38 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH10001002: Using Hibernate built-in connection pool (not for production use!)
Feb 22, 2016 11:54:38 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001005: using driver [com.mysql.jdbc.Driver] at URL [jdbc:mysql://localhost/PROSELYTE_TUTORIAL]
Feb 22, 2016 11:54:38 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {user=root, password=****}
Feb 22, 2016 11:54:38 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
Feb 22, 2016 11:54:38 AM org.hibernate.engine.jdbc.connections.internal.PooledConnections
INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
Mon Feb 22 11:54:38 EET 2016 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
Feb 22, 2016 11:54:39 AM org.hibernate.dialect.Dialect
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect
Adding company record...
Creating developer's records...
List of Developers:
Feb 22, 2016 11:54:40 AM org.hibernate.hql.internal.QueryTranslatorFactoryInitiator initiateService
INFO: HHH000397: Using ASTQueryTranslatorFactory
Developer:
id: 1
First Name: Proselyte
Last Name: Developer
Specialty: Java Developer
Experience: 2
Company: Company:
Company ID: 1
Company Name: Proselyte.net
================
Developer:
id: 2
First Name: Peter
Last Name: Programmer
Specialty: C++ Developer
Experience: 2
Company: Company:
Company ID: 1
Company Name: Proselyte.net
================
Updating experience of Proselyte to 3 years and removing Peter...
Final list of Developers:
Developer:
id: 1
First Name: Proselyte
Last Name: Developer
Specialty: Java Developer
Experience: 3
Company: Company:
Company ID: 1
Company Name: Proselyte.net
================
Feb 22, 2016 11:54:40 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
INFO: HHH10001008: Cleaning up connection pool [jdbc:mysql://localhost/PROSELYTE_TUTORIAL]
В этой статье мы рассмотрели пример использования ассоциации Many-to-One.