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Today, we are going to show you insert multiple records/objects in a database table, using Hibernate Query Language(HQL). To do this, Hibernate doesn't provide a direct insert into values SQL command, but we rather have to retrieve a record from an existing database table(representing an Entity class) and insert this record into another database table(representing another Entity class).

Note : Both Entity classes need to have the same properties, for insert operation to take place successfully.

Note :

• In the upcoming example, We are going to create a Java class which will be mapped to a table in our database(Oracle Express Edition 10g). We are going to use some Hibernate Annotations, hence, there will be no need to create the mapping-resource with extension hbm.xml . For those who are not aware of Hibernate Annotations, please read Hibernate Annotations for reference.


• And yes, one more thing, we are going to create this program in an Integrated Development Environment (IDE), so you may use any IDE of your choice.







Creating an Entity class



We are going to create a general parent class that will contain all the Java code files representing our Model class(whose objects needs to be persisted).

This is a simple Java class whose objects needs to be persisted/saved, these objects are also known as Plain Old Java Objects(POJO) or Entity class. Some may even refer to such class whose objects needs to be persisted as the Model class. This class is an entity class, hence it will be preceded with the @Entity annotation plus a few other annotations described below.

UserInfo.java

package decodejava;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table (name ="USER_INFO")
public class UserInfo {
@Id
@GeneratedValue
@Column (name = "ID")
private int id;
	
@Column (name = "First_Name")
private String firstName;
	
@Column (name = "Last_Name")
private String lastName;	
	


public int getId() 
{
	return id;
}
	


public void setId(int id) 
{
	this.id = id;
}
	

public String getFirstName() 
{
	return firstName;
}


public void setFirstName(String firstName) 
{
	this.firstName = firstName;
}


public String getLastName() 
{
	return lastName;
}


public void setLastName(String lastName) 
{
	this.lastName = lastName;
}
}








Creating a second Entity class



We are going to create another Entity class which contains the backup user data and its objects need to be persisted/saved using Hibernate. Using the object of this class we will perform the insert operation with the database, which will insert the object of this class in a database table containing the object of first Entity class.

Note :
• Both Entity classes need to have the same properties for the insert operation to take place successfully.


• We are going to use a different id generator(@SequenceGenetator) for this entity class as compared to id generator used for the first entity class, in order to have a default value of 1 for the id property of the first element of this class, otherwise if both the classes are using the same id generator then the value of id is carry forwarded for the elements of one class to another.



BackupDatabase.java

package decodejava;

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Transient;

@Entity
@Table (name ="Backup_Database")
public class BackupDatabase 
{
@Id
@Column(name="ID")
@SequenceGenerator(name = "id_generator", sequenceName = "id_seq")
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "id_generator")
private int id;
	
@Column (name = "First_Name")
private String firstName;
	
@Column (name = "Last_Name")
private String lastName;	
	


public int getId() 
{
	return id;
}
	


public void setId(int id) 
{
	this.id = id;
}
	

public String getFirstName() 
{
	return firstName;
}


public void setFirstName(String firstName) 
{
	this.firstName = firstName;
}


public String getLastName() 
{
	return lastName;
}


public void setLastName(String lastName) 
{
	this.lastName = lastName;
}
}






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Creating the class that calls the Hibernate API


The Hiber class creates a Configuration object, used to configure the Hibernate. This is the first object we use when using the Hibernate. This object is used to specify the location of a configuration file and mapping document used by Hibernate. Using Configuration object we can create a SessionFactory object, which is eventually used to create a Session object to perform the object persistence operations.


This class will perform a few operations -


• It creates the objects of UserInfo class, which will be persisted in a database table User_Info using the Hibernate


• It also creates objects of BackupDatabase class, which will be also persisted in a separate database table Backup_Database using Hibernate


• Finally, particular records of Backup_Database between id = 3 and 4 are accessed and inserted into User_Info table by an insert operation using Hibernate Query Language.


Note : To begin using Hibernate Query Language, we need to create a Query object, using the Session object.


Hiber.java

package decodejava;

import java.util.List;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.query.Query;


public class Hiber 
{

	public static void main(String[] args) 
	{

	SessionFactory sf=  new Configuration().configure().buildSessionFactory();  
	Session session = sf.openSession();
	

	//Creating the backup database for the first user
	BackupDatabase backupUser1 = new BackupDatabase();
	backupUser1.setFirstName("Fist");
	backupUser1.setLastName("User");
	
	//Creating the backup database for the second user
	BackupDatabase backupUser2 = new BackupDatabase();
	backupUser2.setFirstName("Second");
	backupUser2.setLastName("User");
	
	//Creating the backup database for the third user
	BackupDatabase backupUser3 = new BackupDatabase();
	backupUser3.setFirstName("Third");
	backupUser3.setLastName("User");

	//Creating the backup database for the fourth user
	BackupDatabase backupUser4 = new BackupDatabase();
	backupUser2.setFirstName("Fourth");
	backupUser2.setLastName("User");
	
	//Creating the first object of UserInfo
	UserInfo ob1 = new UserInfo();
	ob1.setFirstName("First");
	ob1.setLastName("User");

	
	//Creating the second object of UserInfo
	UserInfo ob2 = new UserInfo();
	ob2.setFirstName("Second");
	ob2.setLastName("User");
	
	
	session.beginTransaction();
	session.save(backupUser1); //Saving the first BackupDatabase object
	session.save(backupUser2); //Saving the second BackupDatabase object
	session.save(backupUser3); //Saving the third BackupDatabase object
	session.save(backupUser4); //Saving the fourth BackupDatabase object
	session.save(ob1); //Saving the first UserInfoobject
	session.save(ob2); //Saving the second UserInfoobject
	session.getTransaction().commit();
	
	
	
	
	//Retrieving all the records of UserInfo
	Query query1 = session.createQuery("from UserInfo");
	List<UserInfo> collection1 = query1.getResultList();
	System.out.println("Retrieving and displaying details of all the users");
	for(UserInfo object : collection1)
	{
		System.out.println("Id : " + object.getId());
		System.out.println("First Name : " + object.getFirstName());
		System.out.println("Last Name : " + object.getLastName());	
		System.out.println();
	}

	
		
	//Inserting multiple user record of BackupDatabase, between 'id' 3 and 4, into the UserInfo mapped database table.
	session = sf.openSession();
	session.beginTransaction();
	Query query2 = session.createQuery("insert into UserInfo(id, firstName, lastName) select id, firstName, lastName from BackupDatabase where id between 3 and 4");
	System.out.println("Inserting a new record");
	query2.executeUpdate();
	session.getTransaction().commit();

	
	
	//Retrieve and displaying all the updated records of UserInfo
	session = sf.openSession();
	session.beginTransaction();
	Query query2 = session.createQuery("from UserInfo");
	List<UserInfo> collection2 = query2.getResultList();
	System.out.println("Retrieving and displaying the updated details of users");
	for(UserInfo object : collection2)
	{
		System.out.println("Id : " + object.getId());
		System.out.println("First Name : " + object.getFirstName());
		System.out.println("Last Name : " + object.getLastName());	
		System.out.println();
	}
	session.getTransaction().commit();
		
	//closing the session
	session.close();
	}
}








Adding JARs



• We are going to add some JARs files to the build path of our Java project. These JARs make the Hibernate work with our database using a specific JDBC Driver for our particular database.
  
  All these JARs are included in the folder named required(within our Hibernate installation folder). So, we need to add all the JARs in the required to our build path of our Java project.
  
  
• Finally, we are going to add one more JAR file. This is a specific JDBC JAR file(ojdbc14.jar) required by Hibernate to connect to our database(Oracle Express Edition 10g) and perform object-relational mapping and object persistence.


Note : Those who don't know how to add JARs to the build path of your Java project in Eclipse IDE, please refer to our section Adding JARs to your Hibernate project in Eclipse.







Adding a configuration file



• Next, we are going to add a configuration file to our project.
  
  This configuration document ends with an extension .cfg.xml, and it is named as hibernate.cfg.xml.
  
  
  This configuration file is an xml file and it allows us to specify the following features -
  • A database to which Hibernate connects to perform object-relational mapping and object persistence.
  • The JDBC driver class for our specific database, used by the Hibernate to connect to the database.
  • The username and password of database, using which the Hibernate connects to the database.
  • An SQL Dialect, used by the Hibernate to instruct the database.
  • A Entity/POJO class which will be mapped to a database table by Hibernate.
  • A command to echo all the SQL commands which are executed by the Hibernate on stdout.
  • The mapping entity class, used by Hibernate to correctly map the classes(UserInfo and BackupDatabase) to a database table.
  
  
  
  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">oracle.jdbc.driver.OracleDriver</property>
<property name="connection.url">jdbc:oracle:thin:@localhost:1521:XE</property>
<property name="connection.username">system</property>
<property name="connection.password">promila21</property>


<!-- JDBC connection pool (use the built-in) -->
<property name="connection.pool_size">1</property>


<!-- SQL dialect -->
<property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>


<!-- Disable the second-level cache  -->
<property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>
        
        
<!-- Echo all executed SQL to stdout -->
<property name="show_sql">true</property>


<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">create</property>


<!-- Names the mapping entity class -->
<mapping class ="decodejava.UserInfo"/>
<mapping class ="decodejava.BackupDatabase"/>

</session-factory>

</hibernate-configuration>








Directory Structure of Hibernate Project






The picture above depicts how and where to arrange POJO/Entity(.java) file and the class(that calls the hibernate into action) in a specific directory structure.

Project Folder - HQLInsertingMultiplerecords is the name of our Project and it is a top-level directory.


• This project folder contains the main package of our project i.e. decodejava, which contains POJO/Entity class file i.e. UserInfo.java and the class that calls the hibernate into action i.e. Hiber.java.



• Besides this, the project folder also contains the hibernate configuration file i.e. hibernate.cfg.xml, and as we have used some Hibernate Annotations in this project, hence, there will be no need to create the mapping-resource with extension hbm.xml .



• The project folder also contains all the needed Hibernate JARs present in the required folder of Hibernate installation and the JDBC JAR file(ojdbc14.jar) required by Hibernate to connect to our database.







Execution


When you execute the Hiber.java class, creates two tables -
• User_Info, containing the persisted objects of UserInfo class.
• Backup_Database, containing the persisted objects of BackupDatabase class.

And finally, a particular record of Backup_Database is accessed and inserted into User_Info table by an insert operation using Hibernate Query Language.

See the following output on execution of Hiber.java class-



Hibernate: create sequence hibernate_sequence start with 1 increment by 1
Hibernate: create sequence id_seq start with 1 increment by 50
Hibernate: create table Backup_Database (ID number(10,0) not null, First_Name varchar2(255 char), Last_Name varchar2(255 char), primary key (ID))
Hibernate: create table USER_INFO (ID number(10,0) not null, First_Name varchar2(255 char), Last_Name varchar2(255 char), primary key (ID))
Hibernate: select hibernate_sequence.nextval from dual
Hibernate: select hibernate_sequence.nextval from dual
Hibernate: select id_seq.nextval from dual
Hibernate: select id_seq.nextval from dual
Hibernate: insert into USER_INFO (First_Name, Last_Name, ID) values (?, ?, ?)
Hibernate: insert into USER_INFO (First_Name, Last_Name, ID) values (?, ?, ?)
Hibernate: insert into Backup_Database (First_Name, Last_Name, ID) values (?, ?, ?)
Hibernate: insert into Backup_Database (First_Name, Last_Name, ID) values (?, ?, ?)
Hibernate: insert into Backup_Database (First_Name, Last_Name, ID) values (?, ?, ?)
Hibernate: insert into Backup_Database (First_Name, Last_Name, ID) values (?, ?, ?)
Hibernate: select userinfo0_.ID as ID1_1_, userinfo0_.First_Name as First_Name2_1_, userinfo0_.Last_Name as Last_Name3_1_ from USER_INFO userinfo0_
Retrieving and displaying details of all the users in User_Details
Id : 1
First Name : First
Last Name : User

Id : 2
First Name : Second
Last Name : User

Inserting a new record in User_Details from Backup_Database
Hibernate: insert into USER_INFO ( ID, First_Name, Last_Name ) select backupdata0_.ID as col_0_0_, backupdata0_.First_Name as col_1_0_, backupdata0_.Last_Name as col_2_0_ from Backup_Database backupdata0_ where backupdata0_.ID between 3 and 4
Hibernate: select userinfo0_.ID as ID1_1_, userinfo0_.First_Name as First_Name2_1_, userinfo0_.Last_Name as Last_Name3_1_ from USER_INFO userinfo0_
Retrieving and displaying the updated content User_Details
Id : 1
First Name : First
Last Name : User

Id : 2
First Name : Second
Last Name : User

Id : 3
First Name : Third
Last Name : User

Id : 4
First Name : Fourth
Last Name : User


This output shows you all the SQL commands executed by the Hibernate within the database to create the two tables and save the objects and finally inserting multiple records/objects from Backup_Database table to User_Info table, using Hibernate Query Language command, which also gets translated to an SQL command as you can see in the output above.



You can additionally query the database and see what are the contents of these tables.



• select * from User_Info;








This table shows you the objects of class UserInfo class mapped by Hibernate to a table named User_Info in the database containing the newly inserted multiple records.




• select * from Backup_Database; 








This table shows you the objects of class BackupDatabase class mapped by Hibernate to a table named Backup_Database in the database.






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