Представим ситуацию, когда у нас есть несколько проектов, в каждом из кторых учавтсвуют несколько разработчиков. Для такого варианта подходит ассоциация Many-to-Many.
Для понимания того, как это работает на практике рассмотрим пример простого приложения.
Пример:
Исходный код проекта можно скачать по ЭТОЙ ССЫЛКЕ.
Шаг 1. Создадим три таблицы в нашей базе данных (далее – БД).
HIBENRATE_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,
PRIMARY KEY(ID)
);
HIBERNATE_PROJECTS
CREATE TABLE HIBERNATE_PROJECTS (
id INT NOT NULL auto_increment,
PROJECT_NAME VARCHAR(50) default NULL,
COMPANY VARCHAR(50) default NULL,
PRIMARY KEY (id)
);HIBERNATE_DEV_PROJECTS (промежуточная таблица, которая сожержит идентификаторы разрабтчика и проекта)
CREATE TABLE HIBERNATE_DEV_PROJECTS (
DEVELOPER_ID INT NOT NULL,
PROJECT_ID INT NOT NULL,
PRIMARY KEY (DEVELOPER_ID, PROJECT_ID)
);
Шаг 2. Создадим POJO – классы
Developer.java
package net.proselyte.hibernate.association.manytomany;
import java.util.Set;
public class Developer {
private int id;
private String firstName;
private String lastName;
private String specialty;
private int experience;
private Set projects;
/**
* Default Constructor
*/
public Developer() {
}
/**
* Plain constructor
*/
public Developer(String firstName, String lastName, String specialty, int experience) {
this.firstName = firstName;
this.lastName = lastName;
this.specialty = specialty;
this.experience = experience;
}
/**
* 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 Set getProjects() {
return projects;
}
public void setProjects(Set projects) {
this.projects = projects;
}
/**
* 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";
}
}
Project.java
package net.proselyte.hibernate.association.manytomany;
public class Project {
private int id;
private String projectName;
private String companyName;
/**
* Constructors
*/
public Project() {
}
public Project(String projectName, String companyName) {
this.projectName = projectName;
this.companyName = companyName;
}
/**
* Getters and Setters
*/
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getProjectName() {
return projectName;
}
public void setProjectName(String projectName) {
this.projectName = projectName;
}
public String getCompanyName() {
return companyName;
}
public void setCompanyName(String companyName) {
this.companyName = companyName;
}
/**
* Methods equals and hashCode for comparing objects
*/
public boolean equals(Object object) {
if (object == null) {
return false;
}
if (!this.getClass().equals(object.getClass())) {
return false;
}
Project object2 = (Project) object;
if ((this.id == object2.getId()) && (this.projectName == object2.getProjectName()) && (this.companyName == object2.getCompanyName())) {
return true;
}
return false;
}
public int hasCode() {
int code = 0;
code = (id + projectName + companyName).hashCode();
return code;
}
@Override
public String toString() {
return "Project:\n" +
"id: " + id +
"\nProject Name: " + projectName +
"\nCompany Name: " + companyName + "\n";
}
}
Шаг 3. Создаём 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_БАЗЫ_ДАННЫХ
</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.manytomany.Developer" table="HIBERNATE_DEVELOPERS">
<meta attribute="class-description">
This class contains developer details.
</meta>
<id name="id" type="int" column="id">
<generator class="native"/>
</id>
<set name="projects" cascade="save-update" table="HIBERNATE_DEV_PROJECTS">
<key column="DEVELOPER_ID" />
<many-to-many column="PROJECT_ID" class="net.proselyte.hibernate.association.manytomany.Project"/>
</set>
<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"/>
</class>
<class name="net.proselyte.hibernate.association.manytomany.Project" table="HIBERNATE_PROJECTS">
<meta attribute="class-description">
This class contains project details.
</meta>
<id name="id" type="int" column="ID">
<generator class="native"/>
</id>
<property name="projectName" column="PROJECT_NAME" type="string"/>
<property name="companyName" column="COMPANY" type="string"/>
</class>
</hibernate-mapping>
Шаг 4. Создаём класс DeveloperRunner.java
DeveloperRunner.java
package net.proselyte.hibernate.association.manytomany;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
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("Creating the set of projects.");
HashSet projects = new HashSet();
projects.add(new Project("Proselyte Tutorial", "proselyte.net"));
projects.add(new Project("SkybleLib", "SkybleSoft"));
System.out.println("Adding developer's records to the DB");
int developerId1 = developerRunner.addDeveloper("Proselyte", "Developer", "Java Developer", 2, projects);
int developerId2 = developerRunner.addDeveloper("Peter", "UI", "UI Developer", 4, projects);
System.out.println("List of developers");
developerRunner.listDevelopers();
System.out.println("===================================");
System.out.println("Updating Proselyte");
developerRunner.updateDeveloper(developerId1, 3);
System.out.println("Final list of developers");
developerRunner.listDevelopers();
System.out.println("===================================");
sessionFactory.close();
}
public int addDeveloper(String firstName, String lastName, String specialty, int experience, Set projects) {
Session session = sessionFactory.openSession();
Transaction transaction = null;
transaction = session.beginTransaction();
Developer developer = new Developer(firstName, lastName, specialty, experience);
developer.setProjects(projects);
int developerId = (int)session.save(developer);
transaction.commit();
session.close();
return developerId;
}
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);
Set projects = developer.getProjects();
for (Project project : projects) {
System.out.println(project);
}
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=7533 -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.manytomany.DeveloperRunner
Feb 22, 2016 12:29:48 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {5.1.0.Final}
Feb 22, 2016 12:29:48 PM org.hibernate.cfg.Environment
INFO: HHH000206: hibernate.properties not found
Feb 22, 2016 12:29:48 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
Feb 22, 2016 12:29:48 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager
INFO: HCANN000001: Hibernate Commons Annotations {5.0.1.Final}
Feb 22, 2016 12:29:50 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH10001002: Using Hibernate built-in connection pool (not for production use!)
Feb 22, 2016 12:29:50 PM 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 12:29:50 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {user=root, password=****}
Feb 22, 2016 12:29:50 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
Feb 22, 2016 12:29:50 PM org.hibernate.engine.jdbc.connections.internal.PooledConnections
INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
Mon Feb 22 12:29:50 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 12:29:50 PM org.hibernate.dialect.Dialect
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect
Creating the set of projects.
Adding developer's records to the DB
List of developers
Feb 22, 2016 12:29:51 PM org.hibernate.hql.internal.QueryTranslatorFactoryInitiator initiateService
INFO: HHH000397: Using ASTQueryTranslatorFactory
Developer:
id: 1
First Name: Proselyte
Last Name: Developer
Specialty: Java Developer
Experience: 3
================
Developer:
id: 3
First Name: Proselyte
Last Name: Developer
Specialty: Java Developer
Experience: 2
Project:
id: 2
Project Name: Proselyte Tutorial
Company Name: proselyte.net
Project:
id: 1
Project Name: SkybleLib
Company Name: SkybleSoft
================
Developer:
id: 4
First Name: Peter
Last Name: UI
Specialty: UI Developer
Experience: 4
Project:
id: 2
Project Name: Proselyte Tutorial
Company Name: proselyte.net
Project:
id: 1
Project Name: SkybleLib
Company Name: SkybleSoft
================
===================================
Updating Proselyte
Final list of developers
Developer:
id: 1
First Name: Proselyte
Last Name: Developer
Specialty: Java Developer
Experience: 3
================
Developer:
id: 3
First Name: Proselyte
Last Name: Developer
Specialty: Java Developer
Experience: 3
Feb 22, 2016 12:29:51 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
Project:
INFO: HHH10001008: Cleaning up connection pool [jdbc:mysql://localhost/PROSELYTE_TUTORIAL]
id: 1
Project Name: SkybleLib
Company Name: SkybleSoft
Project:
id: 2
Project Name: Proselyte Tutorial
Company Name: proselyte.net
================
Developer:
id: 4
First Name: Peter
Last Name: UI
Specialty: UI Developer
Experience: 4
Project:
id: 1
Project Name: SkybleLib
Company Name: SkybleSoft
Project:
id: 2
Project Name: Proselyte Tutorial
Company Name: proselyte.net
================
===================================
В этой тстаье мы рассмотрели пример приложения с использованием ассоциации Many-to-Many.