Hibernate Session Methods: get() vs load()
Hibernate Session provides different methods to fetch data from the database. Two of them are – get() and load(). There are also a lot of overloaded methods for these, that we can use in different circumstances. At first look both get() and load() seem similar because both of them fetch the data from the database; however, there are few differences between them. Let’s look at them with a simple example.
Code Example
package com.journaldev.hibernate.main;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import com.journaldev.hibernate.model.Employee;
import com.journaldev.hibernate.util.HibernateUtil;
public class HibernateGetVsLoad {
public static void main(String[] args) {
//Prep Work
SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();
//Get Example
Employee emp = (Employee) session.get(Employee.class, new Long(2));
System.out.println("Employee get called");
System.out.println("Employee ID= " + emp.getId());
System.out.println("Employee Get Details:: " + emp + "\n");
//load Example
Employee emp1 = (Employee) session.load(Employee.class, new Long(1));
System.out.println("Employee load called");
System.out.println("Employee ID= " + emp1.getId());
System.out.println("Employee load Details:: " + emp1 + "\n");
//Close resources
tx.commit();
sessionFactory.close();
}
}
Output
Hibernate: select employee0_.emp_id as emp_id1_1_0_, employee0_.emp_name as emp_name2_1_0_, employee0_.emp_salary as emp_sala3_1_0_, address1_.emp_id as emp_id1_0_1_, address1_.address_line1 as address_2_0_1_, address1_.city as city3_0_1_, address1_.zipcode as zipcode4_0_1_ from EMPLOYEE employee0_ left outer join ADDRESS address1_ on employee0_.emp_id=address1_.emp_id where employee0_.emp_id=?
Employee get called
Employee ID= 2
Employee Get Details:: Id= 2, Name= David, Salary= 200.0, {Address= AddressLine1= Arques Ave, City=Santa Clara, Zipcode=95051}
Employee load called
Employee ID= 1
Hibernate: select employee0_.emp_id as emp_id1_1_0_, employee0_.emp_name as emp_name2_1_0_, employee0_.emp_salary as emp_sala3_1_0_, address1_.emp_id as emp_id1_0_1_, address1_.address_line1 as address_2_0_1_, address1_.city as city3_0_1_, address1_.zipcode as zipcode4_0_1_ from EMPLOYEE employee0_ left outer join ADDRESS address1_ on employee0_.emp_id=address1_.emp_id where employee0_.emp_id=?
Employee load Details:: Id= 1, Name= Pankaj, Salary= 100.0, {Address= AddressLine1= Albany Dr, City=San Jose, Zipcode=95129}
Behavior When Data Does Not Exist
From the output, it’s clear that get() returns the object by fetching it from the database or from Hibernate cache, whereas load() just returns the reference of an object that might not actually exist. It loads the data from the database or cache only when you access other properties of the object. Now let’s try to fetch data that doesn’t exist in the database.
Code Example
//Get Example
try {
Employee emp = (Employee) session.get(Employee.class, new Long(200));
System.out.println("Employee get called");
if (emp != null) {
System.out.println("Employee GET ID= " + emp.getId());
System.out.println("Employee Get Details:: " + emp + "\n");
}
} catch (Exception e) {
e.printStackTrace();
}
//load Example
try {
Employee emp1 = (Employee) session.load(Employee.class, new Long(100));
System.out.println("Employee load called");
System.out.println("Employee LOAD ID= " + emp1.getId());
System.out.println("Employee load Details:: " + emp1 + "\n");
} catch (Exception e) {
e.printStackTrace();
}
Output
Hibernate: select employee0_.emp_id as emp_id1_1_0_, employee0_.emp_name as emp_name2_1_0_, employee0_.emp_salary as emp_sala3_1_0_, address1_.emp_id as emp_id1_0_1_, address1_.address_line1 as address_2_0_1_, address1_.city as city3_0_1_, address1_.zipcode as zipcode4_0_1_ from EMPLOYEE employee0_ left outer join ADDRESS address1_ on employee0_.emp_id=address1_.emp_id where employee0_.emp_id=?
Employee get called
Employee load called
Employee LOAD ID= 100
Hibernate: select employee0_.emp_id as emp_id1_1_0_, employee0_.emp_name as emp_name2_1_0_, employee0_.emp_salary as emp_sala3_1_0_, address1_.emp_id as emp_id1_0_1_, address1_.address_line1 as address_2_0_1_, address1_.city as city3_0_1_, address1_.zipcode as zipcode4_0_1_ from EMPLOYEE employee0_ left outer join ADDRESS address1_ on employee0_.emp_id=address1_.emp_id where employee0_.emp_id=?
org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [com.journaldev.hibernate.model.Employee#100]
at org.hibernate.internal.SessionFactoryImpl$1$1.handleEntityNotFound(SessionFactoryImpl.java:253)
at org.hibernate.proxy.AbstractLazyInitializer.checkTargetState(AbstractLazyInitializer.java:262)
at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:176)
at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:286)
at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185)
at com.journaldev.hibernate.model.Employee_$$_jvst407_1.toString(Employee_$$_jvst407_1.java)
at java.lang.String.valueOf(String.java:2847)
at java.lang.StringBuilder.append(StringBuilder.java:128)
at com.journaldev.hibernate.main.HibernateExample.main(HibernateExample.java:36)
Look at the output closely, when we use get() to retrieve data that doesn’t exists, it returns null. That makes sense because it try to load the data as soon as it’s called. With load(), we are able to print the id but as soon as we try to access other fields, it fires database query and throws org.hibernate.ObjectNotFoundException if there is no record found with the given identifier. It’s hibernate specific Runtime Exception, so we don’t need to catch it explicitly. Let’s look at some of the overloaded methods too. Above get() and load() methods could have been written as below too.
Employee emp = (Employee) session.get("com.journaldev.hibernate.model.Employee", new Long(2));
Employee emp1 = (Employee) session.load("com.journaldev.hibernate.model.Employee", new Long(1));
Employee emp2 = new Employee();
session.load(emp1, new Long(1));
Summary of Hibernate Session get() vs load()
get()loads the data as soon as it’s called whereasload()returns a proxy object and loads data only when it’s actually required, soload()is better because it supports lazy loading.- Since
load()throws an exception when data is not found, we should use it only when we know the data exists. - We should use
get()when we want to make sure the data exists in the database.
That’s all for Hibernate get and load methods. I hope it will clear some doubts and help you in deciding which one to use in different scenarios.
