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

Hibernate Annotation
For one-to-many in Hibernate annotation, please refer to this example.

Download it – Hibernate-one-to-many-xml-mapping.zip (10KB)

Reference

Hibernate Documentation – one to many relationship.

Any Java questions or problems? please post at this JavaNullPointer.com forum, see you there ~

[ Read More ] You can find more similar articles at Hibernate Tutorials

31 Comments

hjc says:
January 17, 2012 at 8:38 am
Hi mkyong,
Nice article.
I am a noob to hibernate. Your tutorials are very helpful in understanding the core concepts since examples are provided. Appreciate it.
I had a question. If I try to run the above program for first time, the parameters are all inserted into stock and stock_daily_record tables correctly. However when I try to run this again, I get the exception below. I may be wrong, but I thought hibernate would detect if there was a duplicate insertion and not insert the values.
Caused by: java.sql.SQLException: Duplicate key or integrity constraint violation message from server: “Duplicate entry ’7052′ for key ‘STOCK_CODE’”
How to handle the exception gracefully?
Thanks
- mkyong says:
  January 18, 2012 at 8:00 am
  Because STOCK_CODE need to be unique. Hibernate is prompts exception is expected.
  You need to add your own checking like this
  find if key exists = true
  ignore and prompt key is duplicated.
  else
  insert record
Jaya says:
November 29, 2011 at 2:15 am
In One to Many Example
why you have to specify (StockDailyRecord.hbm.xml)
I don’t understand , Please can you explain
Ayesha says:
November 15, 2011 at 1:42 pm
can u give a similar example for many to many mapping?
Prateek says:
September 12, 2011 at 5:06 pm
```
very nice way to submit this article
```

Neliel says:

August 8, 2011 at 11:41 am

Hi Mkyong,

Can you help me with my mapping? I am in doubt on whats the best approach?

I have an insurance table and user could change the rate plan associated with it.

Table Insurance:
    id long;
    accountHolder varchar;
    ratePlanId int;  --&gt;Rate Plan Id is Foreign Key to the RatePlanTable
 
Table RatePlan:
    ratePlanId int;
    ratePlanDesc varchar;
    discountRate double;

I have a class structure like this:

public class Insurance{
	private long id;
    private String accountHolder;
    private int ratePlanId;
}
public class RatePlan{
	private int ratePlanId;
    private String ratePlanDesc;
    private double discountRate;
}

Is my table-class hierarchy correct?
or should I change my Insurance class to this?

public class Insurance{
	private long id;
    private String accountHolder;
    private RatePlan plan;
}

What should be the proper mapping? Is this a one-to-many mapping also?

mkyong says:
August 9, 2011 at 1:20 pm
Try Hibernate tool – http://www.mkyong.com/hibernate/how-to-generate-code-with-hibernate-tools/ , it will generate Hibernate mapping automatically, and customize it if require.

Hibernate – One-to-many relationship example (Annotation) says:
April 26, 2011 at 3:27 pm
[...] this tutorial, it will reuse the entire infrastructure of the previous “Hibernate one to many relationship example – XML mapping” tutorial, enhance it to support [...]
toton says:
April 12, 2011 at 12:53 pm
Hi..
in hibernate there is association mapping,collection mapping…component mapping and then one to many vice versa and also uni/bi directional..a bit confusing sometimes..can u provide some light on this
- mkyong says:
  April 12, 2011 at 10:27 pm
  thanks for the suggestion, i’m seeing a lot missing chapters in the current Hibernate tutorials as well, will create more examples in future.
ahdiblack says:
April 5, 2011 at 5:58 am
Hi,
I need help. I have entities like in your tutorial, but in my project, I need to retrieve an entity (like “stock” in your tutorial) as list and in that list I should reach the related entity (like “stock_daily_record” in the tutorial) in a loop and get the values in that entity. But I got lazy initialization erro when I do that. What may be the reason, could you help please??
- mkyong says:
  April 5, 2011 at 8:35 am
  What’s your error stacks?
  - ahdiblack says:
    April 5, 2011 at 9:03 pm
    Here is my error stack
    Caused by: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role:
    - mkyong says:
      April 5, 2011 at 10:27 pm
      Send your full error stack and source code to my mail.
Gregg says:
March 30, 2011 at 2:05 am
In your test code posted above, you do:
session.save(stockDailyRecords);
session.save(stock);
However, this generates an error (for me at least). I believe it should be:
session.save(stock);
session.save(stockDailyRecords);
(It is this way in the zip file, so that doesn’t need corrected.)
- mkyong says:
  March 30, 2011 at 2:39 pm
  Er…Do you means that the code sequence in Zip file is correct, but the code in above posted article is wrong?
  - Muthu krishnan says:
    June 23, 2011 at 10:34 pm
    Hi i am just learner of hibernate,
    we deals with one to many relationship, stock object we create, it contains stockdetailrecord set . you creating instance for stock through which you adding a record for stockdetailrecord. but while saving you calling session.save(stockdetailrecord) then how it will update stock table. because stock table haveing forginekey column in stock_detail_record table. hope it will be like session.save(stock) which interns update stock_detail_record, stock is parent and stock_detail_record is child rite… If i am wrong pl correct me.
    - mkyong says:
      June 24, 2011 at 8:32 am
      Assign parent to his child, configure inverse = true in parent.
      As long as you are assigning the correct nested parent or child, Hibernate will take care of the relationship automatically.
      stockDailyRecords.setStock(stock); session.save(stockdetailrecord)
AG says:
January 29, 2011 at 9:53 pm
Thanks a lot
Very concise & straightforward articles… really helpful.
Keep it up !
AG
PS : One small issue is with the link ‘read more about it…’.
- mkyong says:
  January 31, 2011 at 8:19 am
  Thank for your link check, now the link is updated and working fine.
puri jagan says:
January 8, 2011 at 1:38 pm
how many files needed to create a hibernate & which folder we have to placed tell me plz……….
- mkyong says:
  January 8, 2011 at 10:17 pm
  Just download this project and find it out yourself
Janel Rulpo says:
December 20, 2010 at 10:44 pm
Thanks for putting this out. Helpful info indeed
Hibernate – Cascade example (save, update, delete and delete-orphan) says:
November 14, 2010 at 1:09 am
[...] the collection mapping to manage the state of the collection automatically. In this tutorials, this one-to-many example will be used to demonstrate the cascade [...]
Hibernate Tutorials | Tutorials says:
May 1, 2010 at 1:18 pm
[...] One-to-many relationship example A one-to-many relationship project demonstration. [...]
Amit says:
March 6, 2010 at 10:44 am
Nice article !. One question : Is it necessary to have a many-to-one relationship always on the other side of the one-to-many relationship (like the one you mentioned above) or it’s needed only in specific cases (if yes what are they) ?
- mkyong says:
  March 7, 2010 at 3:29 pm
  yes, configure the relationship in both sides are always recommended, else the other site (many-to-one) or stock_daily_record can not retrieve the data from stock table directly, you may need some workaround for it.
  If you really sure the other site (many-to-one) should not have the relationship, you can just disable it, the Hibernate will still work. But you have to manage both relationship manually. In most cases, it just doesn’t make sense.
  - Amit says:
    March 9, 2010 at 6:44 am
    ok great…thanks for the reply
  - Shikhar says:
    March 21, 2011 at 8:58 pm
    Hey yong…thanks for posting such a nice article….but i’m facing some issues with the one-to-many mapping…actually instead of Set i’m using a List..can you please provide any example with on-to-many relationship involving List??
Hibernate mutable example (class and collection) | Hibernate says:
February 18, 2010 at 10:15 am
[...] will take this one-to-many example for the mutable demonstration. In this mapping file, a Stock is belong to many StockDailyRecord. [...]
Cascade – JPA & Hibernate annotation common mistake | Hibernate says:
February 6, 2010 at 1:35 am
[...] the program failed to execute the cascade operation to the related entities. I will take this one-to-many hibernate example for the [...]

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

Project Structure

Project Dependency

1. “One-to-many” example

2. Hibernate Model Class

3. Hibernate XML Mapping

4. Hibernate Configuration File

5. Run It

Reference

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