Depending on the capabilities of the database, Hibernate maps Double values to the following JDBC types
a. DOUBLE,
b. FLOAT,
c. REAL or
d. NUMERIC
Depending on the capabilities of the database, Hibernate maps Float values to the following JDBC types
a. FLOAT,
b. REAL or
c. NUMERIC
For example,
@Entity
@Table(name = "double_float_demo")
public class DoubleFloatDemo {
@Id
private Integer id;
private Double d;
private Float f;
.........
.........
}
Hibernate generates following DDL for above entity class.
create table double_float_demo (
id integer not null,
d float(53),
f float4,
primary key (id)
)
PostgreSQL accepts float(1) to float(24) as selecting the real type, while float(25) to float(53) to select double precision.
Find the below working application.
Step 1: Create new maven project ‘hibernate-double-float-type-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-double-float-type-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>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>42.4.1</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 DoubleFloatDemo entity class.
DoubleFloatDemo.java
package com.sample.app.entity;
import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
@Entity
@Table(name = "double_float_demo")
public class DoubleFloatDemo {
@Id
private Integer id;
private Double d;
private Float f;
public DoubleFloatDemo(Integer id, Double d, Float f) {
this.id = id;
this.d = d;
this.f = f;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Double getD() {
return d;
}
public void setD(Double d) {
this.d = d;
}
public Float getF() {
return f;
}
public void setF(Float f) {
this.f = f;
}
}
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>
<!-- Database Connection settings -->
<property name="connection.driver_class">org.postgresql.Driver</property>
<property name="connection.url">jdbc:postgresql://127.0.0.1:5432/test</property>
<property name="connection.username">postgres</property>
<property name="connection.password">postgres</property>
<!-- Enable the logging of all the generated SQL statements to the console -->
<property name="show_sql">true</property>
<!-- Format the generated SQL statement to make it more readable, -->
<property name="format_sql">true</property>
<!-- Hibernate will put comments inside all generated SQL statements to
hint what’s the generated SQL trying to do -->
<property name="use_sql_comments">false</property>
<property name="dialect">org.hibernate.dialect.PostgreSQLDialect</property>
<property name="hbm2ddl.auto">update</property>
<!-- mappings for annotated classes -->
<mapping class="com.sample.app.entity.DoubleFloatDemo" />
</session-factory>
</hibernate-configuration>
Step 5: Define main application class.
App.java
package com.sample.app;
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.DoubleFloatDemo;
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);
}
}
public static void main(final String args[]) {
DoubleFloatDemo p1 = new DoubleFloatDemo(1, 2.2, 3.3f);
try (final Session session = SESSION_FACTORY.openSession()) {
session.beginTransaction();
session.persist(p1);
session.getTransaction().commit();
}
}
}
Total project structure looks like below.
Run App.java, you will see below messages in the console.
Aug 16, 2022 11:27:32 AM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate ORM core version 6.1.2.Final
Aug 16, 2022 11:27:33 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH10001002: Using built-in connection pool (not intended for production use)
Aug 16, 2022 11:27:33 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001005: Loaded JDBC driver class: org.postgresql.Driver
Aug 16, 2022 11:27:33 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001012: Connecting with JDBC URL [jdbc:postgresql://127.0.0.1:5432/test]
Aug 16, 2022 11:27:33 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {password=****, user=postgres}
Aug 16, 2022 11:27:33 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
Aug 16, 2022 11:27:33 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl$PooledConnections <init>
INFO: HHH10001115: Connection pool size: 20 (min=1)
Aug 16, 2022 11:27:33 AM org.hibernate.engine.jdbc.dialect.internal.DialectFactoryImpl logSelectedDialect
INFO: HHH000400: Using dialect: org.hibernate.dialect.PostgreSQLDialect
Aug 16, 2022 11:27:33 AM org.hibernate.metamodel.internal.EntityInstantiatorPojoStandard resolveConstructor
INFO: HHH000182: No default (no-argument) constructor for class: com.sample.app.entity.DoubleFloatDemo (class must be instantiated by Interceptor)
Aug 16, 2022 11:27:33 AM org.hibernate.resource.transaction.backend.jdbc.internal.DdlTransactionIsolatorNonJtaImpl getIsolatedConnection
INFO: HHH10001501: Connection obtained from JdbcConnectionAccess [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess@26fb4d06] 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 double_float_demo (
id integer not null,
d float(53),
f float4,
primary key (id)
)
Aug 16, 2022 11:27:33 AM org.hibernate.engine.transaction.jta.platform.internal.JtaPlatformInitiator initiateService
INFO: HHH000490: Using JtaPlatform implementation: [org.hibernate.engine.transaction.jta.platform.internal.NoJtaPlatform]
Hibernate:
insert
into
double_float_demo
(d, f, id)
values
(?, ?, ?)
Query PostgreSQL to confirm the table ddl and content.
test=# \d+ double_float_demo
Table "public.double_float_demo"
Column | Type | Collation | Nullable | Default | Storage | Compression | Stats target | Description
--------+------------------+-----------+----------+---------+---------+-------------+--------------+-------------
id | integer | | not null | | plain | | |
d | double precision | | | | plain | | |
f | real | | | | plain | | |
Indexes:
"double_float_demo_pkey" PRIMARY KEY, btree (id)
Access method: heap
test=#
test=#
test=# SELECT * FROM double_float_demo;
id | d | f
----+-----+-----
1 | 2.2 | 3.3
(1 row)
You can download the complete working application from this link.
Previous Next Home
No comments:
Post a Comment