Во всех предыдущих примерах мы использовали конфигурационные XML – файлы для конфигурирования Hibernate. В этих XML – файлах мы указывали Hibernate с какой таблицей в нешей базе данных (далее – БД) необходимо связать тот или иной POJO – класс и к каким колонкам относятся те или иные поля в этом классе.
Но в Hibernate предусмотрена возможность конфигурирования прилоения с помощью аннотаций.
Аннотации являются мощным иструментом для предоставления метаданных, а также намного нагляднее при чтении нашего кода другим разработчиком.
Обязательными аннотациями являются следующие:
@Entity
Эта аннотация указывает Hibernate, что данный класс является сущностью (entity bean). Такой класс должен иметь конструктор по-умолчанию (пустой конструктор).
@Table
С помощью этой аннотации мы говорим Hibernate, с какой именно таблицей необходимо связать (map) данный класс. Аннотация @Table имеет различные аттрибуты, с помощью которых мы можем указать имя таблицы, каталог, БД и уникальность столбцов в таблец БД.
@Id
С помощью аннотации @Id мы указываем первичный ключ (Primary Key) данного класса.
@GeneratedValue
Эта аннотация используется вместе с аннотацией @Id и определяет такие паметры, как strategy и generator.
@Column
Аннотация @Column определяет к какому столбцу в таблице БД относится конкретное поле класса (аттрибут класса).
Наиболее часто используемые аттрибуты аннотации @Column такие:
- name
Указывает имя столбца в таблице - unique
Определяет, должно ли быть данноезначение уникальным - nullable
Определяет, может ли данное поле быть NULL, или нет. - length
Указывает, какой размер столбца (например колчиство символов, при использовании String).
Для понимания того, как это работает на практике, рассмотрим пример небольшого приложения.
Пример:
Исходный код проекта можно скачать по ЭТОЙ ССЫЛКЕ.
Шаг 1. Создадим таблцу в нашей 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)
);Шаг 2. Создадим POJO – класс.
Developer.java
package net.proselyte.hibernate.annotations;
import javax.persistence.*;
@Entity
@Table(name = "HIBERNATE_DEVELOPERS")
public class Developer {
@Id
@GeneratedValue (strategy = GenerationType.AUTO)
@Column (name = "id")
private int id;
@Column (name = "FIRST_NAME")
private String firstName;
@Column (name = "LAST_NAME")
private String lastName;
@Column (name = "SPECIALTY")
private String specialty;
@Column (name = "EXPERIENCE")
private int experience;
/**
* 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;
}
/**
* 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";
}
}
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.annotations.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>
<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>
</hibernate-mapping>
Шаг 4. Создадим класс DeveloperRunner.java
DeveloperRunner.java
package net.proselyte.hibernate.annotations;
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 Developer's records to the database");
Integer developerId1 = developerRunner.addDeveloper("Proselyte", "Developer", "Java Developer", 2);
Integer developerId2 = developerRunner.addDeveloper("Some", "Developer", "C++ Developer", 2);
Integer developerId3 = developerRunner.addDeveloper("Peter", "Team Lead", "Java Team Lead", 6);
System.out.println("List of Developers:");
developerRunner.listDevelopers();
System.out.println("Removing \'Some Developer\' and updating \'Proselyte Developer\''s experience:");
developerRunner.removeDeveloper(developerId2);
developerRunner.updateDeveloper(developerId1, 3);
System.out.println("Final list of Developers:");
developerRunner.listDevelopers();
sessionFactory.close();
}
public Integer addDeveloper(String firstName, String lastName, String specialty, int experience) {
Session session = sessionFactory.openSession();
Transaction transaction = null;
Integer developerId = null;
transaction = session.beginTransaction();
Developer developer = new Developer(firstName, lastName, specialty, experience);
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);
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 вы получите, примерно, следующий результат:
/usr/lib/jvm/java-8-oracle/bin/java -Didea.launcher.port=7536 -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.annotations.DeveloperRunner
Feb 22, 2016 9:34:01 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {5.1.0.Final}
Feb 22, 2016 9:34:01 PM org.hibernate.cfg.Environment
INFO: HHH000206: hibernate.properties not found
Feb 22, 2016 9:34:01 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
Feb 22, 2016 9:34:01 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager
INFO: HCANN000001: Hibernate Commons Annotations {5.0.1.Final}
Feb 22, 2016 9:34:02 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH10001002: Using Hibernate built-in connection pool (not for production use!)
Feb 22, 2016 9:34:02 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 9:34:02 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {user=root, password=****}
Feb 22, 2016 9:34:02 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
Feb 22, 2016 9:34:02 PM org.hibernate.engine.jdbc.connections.internal.PooledConnections
INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
Mon Feb 22 21:34:03 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 9:34:03 PM org.hibernate.dialect.Dialect
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect
Adding Developer's records to the database
List of Developers:
Feb 22, 2016 9:34:04 PM org.hibernate.hql.internal.QueryTranslatorFactoryInitiator initiateService
INFO: HHH000397: Using ASTQueryTranslatorFactory
Developer:
id: 1
First Name: Proselyte
Last Name: Developer
Specialty: Java Developer
Experience: 2
================
Developer:
id: 2
First Name: Some
Last Name: Developer
Specialty: C++ Developer
Experience: 2
================
Developer:
id: 3
First Name: Peter
Last Name: Team Lead
Specialty: Java Team Lead
Experience: 6
================
Removing 'Some Developer' and updating 'Proselyte Developer''s experience:
Final list of Developers:
Developer:
id: 1
First Name: Proselyte
Last Name: Developer
Specialty: Java Developer
Experience: 3
================
Developer:
id: 3
First Name: Peter
Last Name: Team Lead
Specialty: Java Team Lead
Experience: 6
================
Так будет выглядеть наша таблица HIBERNATE_DEVELOPERS в БД
+----+------------+-----------+----------------+------------+
| ID | FIRST_NAME | LAST_NAME | SPECIALTY | EXPERIENCE |
+----+------------+-----------+----------------+------------+
| 1 | Proselyte | Developer | Java Developer | 3 |
| 3 | Peter | Team Lead | Java Team Lead | 6 |
+----+------------+-----------+----------------+------------+
В этой статье мы изучили основы конфигурирования Hibernate с помощью аннотаций и рассмотрели пример простого приложения с их использованием.