Difference Between Hibernate get() and load() Methods ?

What is the difference between hibernate get() and load() methods ? this is one of the famous hibernate interview questions,  most of us will use hibernate get and load methods irrespective of knowing their exact behavior 🙂 will you accept that ? of course even myself too in the initial stages 🙂 Today i will try to clear that confusion.

Few Points About Hibernate get() & load()

• Both are from Session interface, and we will call them as session.get() & session.load()
• Both will be use for retrieving the object (a row) from the database

Then what’s the difference them ? lets start with load() and then get() method.

Consider a Student class having 3 properties stdId, stdName, stdCountry

1. session.load()

• When you call session.load() method, it will always return a “proxy” object,  whats the meaning of proxy object ?
• Proxy means, hibernate will prepare some fake object with given identifier value in the memory without hitting the database, for example if we call session.load(Student.class,new Integer(107));  > hibernate will create one fake Student object [row] in the memory with id 107, but remaining properties of Student class will not even be initialized, observe this graphical representation…
  
• It will hit the database only when we try to retrieve the other properties of Student object i mean stdName, stdCountry.  If we call s2.getStdName() then hibernate will hit the database and search the row with student id 107 and retrieve the values, if object [row] not found in the database it will throws ObjectNotFoundException.,

Let me explain each point by taking an example

Example of session.load()

index.jsp:

System.out.println("Student is calling with load()");        
s2 =(Student) session.load(Student.class,new Integer(107));    
System.out.println("Student called with load()");
System.out.println("Printing Student Name___"+s2.getStdtId());        
System.out.println("Printing Student Name___"+s2.getStdName());

Output

Explanation:

In index.jsp > line number 4,  i have called s2.getStdtId() and hibernate simply printed 107 [at Output > line number 3] without creating any database query why ? because as i have explained hibernate will prepare some fake object with given identifier value in the memory without hitting the database.  So when we call load() method (at index.jsp > line number 2 ) with 107 value, hibernate will create a fake object with 107 as identifier value, i mean temporarily it will consider the student id as 107.  If you observe the output, hibernate was generated the database query (at Output > line number 4 )  when we called s2.getStdName(); ( index.jsp > line number 5 ).

That’s it, so finally we came to know that session.load() will hit the database only when we start retrieving the object (row) values.

2. session.get()

• When you call session.get() method, it will hit the database immediately and returns the original object
  
• If the row is not available in the database, it returns null

Example of session.get()

System.out.println("Student is calling with get()");        
s1 = (Student) session.get(Student.class,new Integer(107));    
System.out.println("Student called with get()");
System.out.println("Printing Student Name___"+s1.getStdtId());        
System.out.println("Printing Student Name___"+s1.getStdName());

Output

Explanation:

• Nothing to explain here 🙂 as i told, when we call session.get() method hibernate will hit the database and returns the original object [ row ], that’s the reason it was generated a query [ check line number 2 in the output screen]

Hmm…, so which is the best method to use, hibernate load() or get() ? its completely your choice 😉

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::. About the Author .::
		Sivateja Kandula - Java/J2EE Full Stack Developer Founder of Java4s - Get It Yourself, A popular Java/J2EE Programming Blog, Love Java and UI frameworks. You can sign-up for the Email Newsletter for your daily dose of Java tutorials.