By annotating a byte array with @Lob annotation, we can map a byte array to BLOB.
Example
@Lob
private byte[] arr1;
Find the below working application.
Step 1: Create new maven project ‘hibernate-byte-array-to-blob-demo’.
Step 2: Update pom.xml with maven dependencies.
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.sample.app</groupId>
<artifactId>hibernate-byte-array-to-blob-demo</artifactId>
<version>1</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<java.version>15</java.version>
<maven.compiler.source>${java.version}</maven.compiler.source>
<maven.compiler.target>${java.version}</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<version>2.1.214</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>6.1.2.Final</version>
</dependency>
<dependency>
<groupId>javax.persistence</groupId>
<artifactId>javax.persistence-api</artifactId>
<version>2.2</version>
</dependency>
</dependencies>
</project>
Step 3: Define Demo class.
Demo.java
package com.sample.app.entity;
import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.Lob;
import jakarta.persistence.Table;
@Entity
@Table(name = "demo")
public class Demo {
@Id
private int id;
@Lob
private byte[] arr1;
public Demo(int id, byte[] arr1) {
this.id = id;
this.arr1 = arr1;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public byte[] getArr1() {
return arr1;
}
public void setArr1(byte[] arr1) {
this.arr1 = arr1;
}
}
Step 4: Create hibernate.cfg.xml file under src/main/resources folder.
hibernate.cfg.xml
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- JDBC Database connection settings -->
<property name="connection.driver_class">org.h2.Driver</property>
<property name="connection.url">jdbc:h2:mem:test</property>
<property name="connection.username">admin</property>
<property name="connection.password">admin</property>
<property name="connection.pool_size">1</property>
<property name="dialect">org.hibernate.dialect.H2Dialect</property>
<!-- Echo the SQL to stdout -->
<property name="show_sql">true</property>
<property name="format_sql">true</property>
<property name="current_session_context_class">thread</property>
<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">create-drop</property>
<!-- dbcp connection pool configuration -->
<property name="hibernate.dbcp.initialSize">2</property>
<property name="hibernate.dbcp.maxTotal">10</property>
<property name="hibernate.dbcp.maxIdle">5</property>
<property name="hibernate.dbcp.minIdle">3</property>
<property name="hibernate.dbcp.maxWaitMillis">-1</property>
<!-- mappings for annotated classes -->
<mapping class="com.sample.app.entity.Demo" />
</session-factory>
</hibernate-configuration>
Step 5: Define main application class.
App.java
package com.sample.app;
import java.io.IOException;
import java.sql.SQLException;
import java.util.List;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.Metadata;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import com.sample.app.entity.Demo;
import jakarta.persistence.criteria.CriteriaBuilder;
import jakarta.persistence.criteria.CriteriaQuery;
public class App {
private static final SessionFactory SESSION_FACTORY = buildSessionFactory();
private static SessionFactory buildSessionFactory() {
try {
final StandardServiceRegistry standardRegistry = new StandardServiceRegistryBuilder()
.configure("hibernate.cfg.xml").build();
final Metadata metaData = new MetadataSources(standardRegistry).getMetadataBuilder().build();
return metaData.getSessionFactoryBuilder().build();
} catch (Throwable ex) {
throw new ExceptionInInitializerError(ex);
}
}
private static <T> List<T> loadAllData(Class<T> clazz, Session session) {
final CriteriaBuilder builder = session.getCriteriaBuilder();
final CriteriaQuery<T> criteria = builder.createQuery(clazz);
criteria.from(clazz);
return session.createQuery(criteria).getResultList();
}
public static void main(final String args[]) throws IOException, SQLException {
String msg = "Hello World";
byte[] data = msg.getBytes();
Demo e1 = new Demo(1, data);
try (final Session session = SESSION_FACTORY.openSession()) {
session.beginTransaction();
session.persist(e1);
session.flush();
session.getTransaction().commit();
List<Demo> records = loadAllData(Demo.class, session);
for (Demo record : records) {
int id = record.getId();
System.out.println("id : " + id);
byte[] arr1 = record.getArr1();
System.out.println("arr1 : " + new String(arr1));
}
}
}
}
Total project structure looks like below.
Run App.java, you will see below messages in the console.
Aug 17, 2022 3:22:48 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate ORM core version 6.1.2.Final
Aug 17, 2022 3:22:48 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH10001002: Using built-in connection pool (not intended for production use)
Aug 17, 2022 3:22:48 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001005: Loaded JDBC driver class: org.h2.Driver
Aug 17, 2022 3:22:48 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001012: Connecting with JDBC URL [jdbc:h2:mem:test]
Aug 17, 2022 3:22:48 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {password=****, user=admin}
Aug 17, 2022 3:22:48 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
Aug 17, 2022 3:22:48 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl$PooledConnections <init>
INFO: HHH10001115: Connection pool size: 1 (min=1)
Aug 17, 2022 3:22:49 PM org.hibernate.engine.jdbc.dialect.internal.DialectFactoryImpl logSelectedDialect
INFO: HHH000400: Using dialect: org.hibernate.dialect.H2Dialect
Aug 17, 2022 3:22:49 PM org.hibernate.metamodel.internal.EntityInstantiatorPojoStandard resolveConstructor
INFO: HHH000182: No default (no-argument) constructor for class: com.sample.app.entity.Demo (class must be instantiated by Interceptor)
Hibernate:
drop table if exists demo cascade
Aug 17, 2022 3:22:49 PM org.hibernate.resource.transaction.backend.jdbc.internal.DdlTransactionIsolatorNonJtaImpl getIsolatedConnection
INFO: HHH10001501: Connection obtained from JdbcConnectionAccess [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess@2ab26378] for (non-JTA) DDL execution was not in auto-commit mode; the Connection 'local transaction' will be committed and the Connection will be set into auto-commit mode.
Hibernate:
create table demo (
id integer not null,
arr1 blob,
primary key (id)
)
Aug 17, 2022 3:22:49 PM org.hibernate.resource.transaction.backend.jdbc.internal.DdlTransactionIsolatorNonJtaImpl getIsolatedConnection
INFO: HHH10001501: Connection obtained from JdbcConnectionAccess [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess@5115f590] for (non-JTA) DDL execution was not in auto-commit mode; the Connection 'local transaction' will be committed and the Connection will be set into auto-commit mode.
Hibernate:
insert
into
demo
(arr1, id)
values
(?, ?)
Hibernate:
select
d1_0.id,
d1_0.arr1
from
demo d1_0
id : 1
arr1 : Hello World
You can download complete working application from this link.
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