Коллекция Java, в которой хранятся пары “ключ – значение” и в которой допускается хранение только уникальных эелементов, называется Map.
Map связывается (mapped) fс помощью элемента <map> и (в случае нупорядоченной Map) инициализируется с помощью java.util.HashMap.
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 бахе 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,
PRIMARY KEY(ID)
);
HIBERNATE_PROJECTS
create table HIBERNATE_PROJECTS (
id INT NOT NULL auto_increment,
SPHERE VARCHAR(50) default NULL,
PROJECT_NAME VARCHAR(50) default NULL,
COMPANY VARCHAR(50) default NULL,
DEVELOPER_ID INT default NULL,
PRIMARY KEY (id)
);
Мы будем использовать отношение one-to-many между таблицами HIBERNATE_DEVELOPERS и HIBERNATE_PROJECTS.
Шаг 2. Создадим POJO – классы
Developer.java
package net.proselyte.hibernate.mappings.map;
import java.util.Map;
public class Developer {
private int id;
private String firstName;
private String lastName;
private String specialty;
private int experience;
private Map<String, Project> 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 Map<String, Project> getProjects() {
return projects;
}
public void setProjects(Map<String, Project> 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.mappings.map;
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;
}
@Override
public String toString() {
return "Project:\n" +
"id: " + id +
"\nProject Name: " + projectName +
"\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.mappings.map.Developer" table="HIBERNATE_DEVELOPERS">
<meta attribute="class-description">
This class contains developer's details.
</meta>
<id name="id" type="int" column="id">
<generator class="native"/>
</id>
<map name="projects" cascade="all">
<key column="DEVELOPER_ID"/>
<index column="SPHERE" type="string" />
<one-to-many class="net.proselyte.hibernate.mappings.map.Project"/>
</map>
<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.mappings.map.Project" table="HIBERNATE_PROJECTS">
<meta attribute="class-description">
This class contains project's records.
</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.mappings.map;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
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 collection of projects.");
HashMap<String, Project> projects1 = new HashMap<String, Project>();
projects1.put("Computer Science", new Project("Proselyte Tutorial", "proselyte.net"));
projects1.put("Aviation", new Project("SkybleLib", "SkybleSoft"));
HashMap<String, Project> projects2 = new HashMap<String, Project>();
projects2.put("Some Sphere", new Project("Some Project", "Some Company"));
projects2.put("E-commerce", new Project("One more Project", "One more Company"));
System.out.println("Adding developer's records to the DB");
Integer developerId1 = developerRunner.addDeveloper("Proselyte", "Developer", "Java Developer", 2, projects1);
Integer developerId2 = developerRunner.addDeveloper("Peter", "UI", "UI Developer", 4, projects2);
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 Integer addDeveloper(String firstName, String lastName, String specialty, int experience, HashMap<String, Project> projects) {
Session session = sessionFactory.openSession();
Transaction transaction = null;
Integer developerId = null;
transaction = session.beginTransaction();
Developer developer = new Developer(firstName, lastName, specialty, experience);
developer.setProjects(projects);
developerId = (Integer) 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);
Map<String, Project> projects = developer.getProjects();
System.out.println(developer.getFirstName() + "'s projects:\n");
System.out.println(projects);
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 получилм, примерно, следующий результат:
/usr/lib/jvm/java-8-oracle/bin/java -Didea.launcher.port=7540 -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/5.0.7.Final/hibernate-core-5.0.7.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/3.18.1-GA/javassist-3.18.1-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/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/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.mappings.map.DeveloperRunner
Feb 20, 2016 8:30:38 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {5.0.7.Final}
Feb 20, 2016 8:30:38 PM org.hibernate.cfg.Environment
INFO: HHH000206: hibernate.properties not found
Feb 20, 2016 8:30:38 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
Feb 20, 2016 8:30:38 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager
INFO: HCANN000001: Hibernate Commons Annotations {5.0.1.Final}
Feb 20, 2016 8:30:40 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH10001002: Using Hibernate built-in connection pool (not for production use!)
Feb 20, 2016 8:30:40 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 20, 2016 8:30:40 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {user=root, password=****}
Feb 20, 2016 8:30:40 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
Feb 20, 2016 8:30:40 PM org.hibernate.engine.jdbc.connections.internal.PooledConnections
INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
Sat Feb 20 20:30:40 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 20, 2016 8:30:40 PM org.hibernate.dialect.Dialect
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect
Creating the collection of projects.
Adding developer's records to the DB
List of developers
Feb 20, 2016 8:30:41 PM org.hibernate.hql.internal.QueryTranslatorFactoryInitiator initiateService
INFO: HHH000397: Using ASTQueryTranslatorFactory
Developer:
id: 79
First Name: Proselyte
Last Name: Developer
Specialty: Java Developer
Experience: 2
Proselyte's projects:
{Aviation=Project:
id: 21
Project Name: SkybleLib
Company Name: SkybleSoft
, Computer Science=Project:
id: 22
Project Name: Proselyte Tutorial
Company Name: proselyte.net
}
================
Developer:
id: 80
First Name: Peter
Last Name: UI
Specialty: UI Developer
Experience: 4
Peter's projects:
{Some Sphere=Project:
id: 23
Project Name: Some Project
Company Name: Some Company
, E-commerce=Project:
id: 24
Project Name: One more Project
Company Name: One more Company
}
================
===================================
Updating Proselyte
Final list of developers
Developer:
id: 79
First Name: Proselyte
Last Name: Developer
Specialty: Java Developer
Experience: 3
Proselyte's projects:
{Aviation=Project:
id: 21
Project Name: SkybleLib
Company Name: SkybleSoft
, Computer Science=Project:
id: 22
Project Name: Proselyte Tutorial
Company Name: proselyte.net
}
================
Developer:
id: 80
First Name: Peter
Last Name: UI
Specialty: UI Developer
Experience: 4
Peter's projects:
{Some Sphere=Project:
id: 23
Project Name: Some Project
Company Name: Some Company
, E-commerce=Project:
id: 24
Project Name: One more Project
Company Name: One more Company
}
================
===================================
Feb 20, 2016 8:30:41 PM 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 связывания с использованием Map.