Hibernate – One-to-Many example (XML Mapping)

A one-to-many relationship occurs when one entity is related to many occurrences in another entity.

In this tutorial, we show you how to works with one-to-many table relationship in Hibernate, via XML mapping file (hbm).

Tools and technologies used in this tutorials :

Hibernate 3.6.3.Final

MySQL 5.1.15

Maven 3.0.3

Eclipse 3.6

Project Structure

Project structure of this tutorial.

Project Dependency

Get

hibernate.jar

from JBoss repository, Maven will take care all the related dependencies for you

File :

pom.xml

<project ...>

<repositories>
<repository>
<id>JBoss repository</id>
<url>http://repository.jboss.org/nexus/content/groups/public/</url>
</repository>
</repositories>

<dependencies>

<!-- MySQL database driver -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.15</version>
</dependency>

<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>3.6.3.Final</version>
</dependency>

<dependency>
<groupId>javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.12.1.GA</version>
</dependency>

</dependencies>
</project>

1. “One-to-many” example

This is a one-to-many relationship table design, a

STOCK

table has many occurrences

STOCK_DAILY_RECORD

table.



See MySQL table scripts

DROP TABLE IF EXISTS `stock`;
CREATE TABLE `stock` (
`STOCK_ID` int(10) unsigned NOT NULL AUTO_INCREMENT,
`STOCK_CODE` varchar(10) NOT NULL,
`STOCK_NAME` varchar(20) NOT NULL,
PRIMARY KEY (`STOCK_ID`) USING BTREE,
UNIQUE KEY `UNI_STOCK_NAME` (`STOCK_NAME`),
UNIQUE KEY `UNI_STOCK_ID` (`STOCK_CODE`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=34 DEFAULT CHARSET=utf8;

DROP TABLE IF EXISTS `mkyongdb`.`stock_daily_record`;
CREATE TABLE  `mkyongdb`.`stock_daily_record` (
`RECORD_ID` int(10) unsigned NOT NULL AUTO_INCREMENT,
`PRICE_OPEN` float(6,2) DEFAULT NULL,
`PRICE_CLOSE` float(6,2) DEFAULT NULL,
`PRICE_CHANGE` float(6,2) DEFAULT NULL,
`VOLUME` bigint(20) unsigned DEFAULT NULL,
`DATE` date NOT NULL,
`STOCK_ID` int(10) unsigned NOT NULL,
PRIMARY KEY (`RECORD_ID`) USING BTREE,
UNIQUE KEY `UNI_STOCK_DAILY_DATE` (`DATE`),
KEY `FK_STOCK_TRANSACTION_STOCK_ID` (`STOCK_ID`),
CONSTRAINT `FK_STOCK_TRANSACTION_STOCK_ID` FOREIGN KEY (`STOCK_ID`)
REFERENCES `stock` (`STOCK_ID`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=36 DEFAULT CHARSET=utf8;

2. Hibernate Model Class

Create two model classes –

Stock.java

and

StockDailyRecord.java

, to represent the above tables.

File :

Stock.java

package com.mkyong.stock;

import java.util.HashSet;
import java.util.Set;

public class Stock implements java.io.Serializable {

private Integer stockId;
private
effe
String stockCode;
private String stockName;
private Set<StockDailyRecord> stockDailyRecords =
new HashSet<StockDailyRecord>(0);

//getter, setter and constructor
}

File :

StockDailyRecord.java

package com.mkyong.stock;

import java.util.Date;

public class StockDailyRecord implements java.io.Serializable {

private Integer recordId;
private Stock stock;
private Float priceOpen;
private Float priceClose;
private Float priceChange;
private Long volume;
private Date date;

//getter, setter and constructor
}

3. Hibernate XML Mapping

Now, create two Hibernate mapping files (hbm) –

Stock.hbm.xml

and

StockDailyRecord.hbm.xml

.

File :

Stock.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.mkyong.stock.Stock" table="stock" catalog="mkyongdb">
<id name="stockId" type="java.lang.Integer">
<column name="STOCK_ID" />
<generator class="identity" />
</id>
<property name="stockCode" type="string">
<column name="STOCK_CODE" length="10" not-null="true" unique="true" />
</property>
<property name="stockName" type="string">
<column name="STOCK_NAME" length="20" not-null="true" unique="true" />
</property>
<set name="stockDailyRecords" table="stock_daily_record"
inverse="true" lazy="true" fetch="select">
<key>
<column name="STOCK_ID" not-null="true" />
</key>
<one-to-many class="com.mkyong.stock.StockDailyRecord" />
</set>
</class>
</hibernate-mapping>

File :

StockDailyRecord.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.mkyong.stock.StockDailyRecord" table="stock_daily_record"
catalog="mkyongdb">
<id name="recordId" type="java.lang.Integer">
<column name="RECORD_ID" />
<generator class="identity" />
</id>
<many-to-one name="stock" class="com.mkyong.stock.Stock" fetch="select">
<column name="STOCK_ID" not-null="true" />
</many-to-one>
<property name="priceOpen" type="java.lang.Float">
<column name="PRICE_OPEN" precision="6" />
</property>
<property name="priceClose" type="java.lang.Float">
<column name="PRICE_CLOSE" precision="6" />
</property>
<property name="priceChange" type="java.lang.Float">
<column name="PRICE_CHANGE" precision="6" />
</property>
<property name="volume" type="java.lang.Long">
<column name="VOLUME" />
</property>
<property name="date" type="date">
<column name="DATE" length="10" not-null="true" unique="true" />
</property>
</class>
</hibernate-mapping>

4. Hibernate Configuration File

Puts

Stock.hbm.xml

and

StockDailyRecord.hbm.xml

in your Hibernate configuration file, and also MySQL connection details.

File : 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>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/mkyongdb</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">password</property>
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="show_sql">true</property>
<property name="format_sql">true</property>
<mapping resource="com/mkyong/stock/Stock.hbm.xml" />
<mapping resource="com/mkyong/stock/StockDailyRecord.hbm.xml" />
</session-factory>
</hibernate-configuration>

5. Run It

Run it, Hibernate will insert a row into the

STOCK

table and a row into the

STOCK_DAILY_RECORD

table.

File :

App.java

package com.mkyong;

import java.util.Date;

import org.hibernate.Session;

import com.mkyong.stock.Stock;
import com.mkyong.stock.StockDailyRecord;
import com.mkyong.util.HibernateUtil;

public class App {
public static void main(String[] args) {

System.out.println("Hibernate one to many (XML Mapping)");
Session session = HibernateUtil.getSessionFactory().openSession();

session.beginTransaction();

Stock stock = new Stock();
stock.setStockCode("7052");
stock.setStockName("PADINI");
session.save(stock);

StockDailyRecord stockDailyRecords = new StockDailyRecord();
stockDailyRecords.setPriceOpen(new Float("1.2"));
stockDailyRecords.setPriceClose(new Float("1.1"));
stockDailyRecords.setPriceChange(new Float("10.0"));
stockDailyRecords.setVolume(3000000L);
stockDailyRecords.setDate(new Date());

stockDailyRecords.setStock(stock);
stock.getStockDailyRecords().add(stockDailyRecords);

session.save(stockDailyRecords);

session.getTransaction().commit();
System.out.println("Done");
}
}

Output …

Hibernate one to many (XML Mapping)
Hibernate:
insert
into
mkyongdb.stock
(STOCK_CODE, STOCK_NAME)
values
(?, ?)
Hibernate:
insert
into
mkyongdb.stock_daily_record
(STOCK_ID, PRICE_OPEN, PRICE_CLOSE, PRICE_CHANGE, VOLUME, DATE)
values
(?, ?, ?, ?, ?, ?)