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 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        (?, ?, ?, ?, ?, ?)