50+ Top Hibernate Interview Questions and Answers (2023)

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Intermediate / 1 to 5 years experienced level questions & answers

Ques 1. What are Callback interfaces?

These interfaces are used in the application to receive a notification when some object events occur. Like when an object is loaded, saved or deleted. There is no need to implement callbacks in hibernate applications, but they're useful for implementing certain kinds of generic functionality.

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Ques 2. Define cascade and inverse option in one-many mapping?

cascade enable operations to cascade to child entities.
cascade="all|none|save-update|delete|all-delete-orphan"
inverse mark this collection as the "inverse" end of a bidirectional association. inverse="true|false" Essentially "inverse" indicates which end of a relationship should be ignored, so when persisting a parent who has a collection of children, should you ask the parent for its list of children, or ask the children who the parents are?

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Ques 3. What does it mean to be inverse?

It informs hibernate to ignore that end of the relationship. If the one-to-many was marked as inverse, hibernate would create a child->parent relationship (child.getParent). If the one-to-many was marked as non-inverse then a child->parent relationship would be created.

In Hibernate, only the �relationship owner� should maintain the relationship, and the �inverse� keyword is created to defines which side is the owner to maintain the relationship. However the �inverse� keyword itself is not verbose enough, I would suggest change the keyword to �relationship_owner�.

In short, inverse=�true� means this is the relationship owner, and inverse=�false� (default) means it�s not.

Suppose Stock is parent and StockDailyRecords is Child object.

Inverse keyword is applied in one to many relationship. Here�s the question, if save or update operation perform in �Stock� object, should it update the �stockDailyRecords� relationship?

1. inverse=�true�

If inverse=�true� in the set variable, it means �stock_daily_record� is the relationship owner, so Stock will NOT UPDATE the relationship.

2. inverse=�false�

If inverse=�false� (default) in the set variable, it means �stock� is the relationship owner, and Stock will UPDATE the relationship.

If keyword �inverse� is not define, the inverse = �false� will be used, which is

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Ques 4. How do you invoke Stored Procedures?

<sql-query name="selectAllEmployees_SP" callable="true">
<return alias="emp" class="employee">
<return-property name="empid" column="EMP_ID"/>
<return-property name="name" column="EMP_NAME"/>
<return-property name="address" column="EMP_ADDRESS"/> { ? = call selectAllEmployees() }
</return>
</sql-query>

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Ques 5. What is a Session? Can you share a session object between different threads?

Session is a light weight and a non-threadsafe object (No, you cannot share it between threads) that represents a single unit-of-work with the database. Sessions are opened by a SessionFactory and then are closed when all work is complete. Session is the primary interface for the persistence service. A session obtains a database connection lazily (i.e. only when required). To avoid creating too many sessions ThreadLocal class can be used as shown below to get the current session no matter how many times you make call to the currentSession() method.

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Ques 6. What are the benefits of detached objects?

Detached objects can be passed across layers all the way up to the presentation layer without having to use any DTOs (Data Transfer Objects). You can later on re-attach the detached objects to another session.

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Ques 7. What are the pros and cons of detached objects?

Pros:
" When long transactions are required due to user think-time, it is the best practice to break the long transaction up into two or more transactions. You can use detached objects from the first transaction to carry data all the way up to the presentation layer. These detached objects get modified outside a transaction and later on re-attached to a new transaction via another session.

Cons
" In general, working with detached objects is quite cumbersome, and better to not clutter up the session with them if possible. It is better to discard them and re-fetch them on subsequent requests. This approach is not only more portable but also more efficient because - the objects hang around in Hibernate's cache anyway.

" Also from pure rich domain driven design perspective it is recommended to use DTOs (DataTransferObjects) and DOs (DomainObjects) to maintain the separation between Service and UI tiers.

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Ques 8. What is the difference between the session.get() method and the session.load() method?

Both the session.get(..) and session.load() methods create a persistent object by loading the required object from the database. But if there was not such object in the database then the method session.load(..) throws an exception whereas session.get(&) returns null.

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Ques 9. How would you reatach detached objects to a session when the same object has already been loaded into the session?

You can use the session.merge() method call.

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Hibernate Interview Questions and Answers

Intermediate / 1 to 5 years experienced level questions & answers

Ques 1. What are Callback interfaces?

Ques 2. Define cascade and inverse option in one-many mapping?

Ques 3. What does it mean to be inverse?

Ques 4. How do you invoke Stored Procedures?

Ques 5. What is a Session? Can you share a session object between different threads?

Ques 6. What are the benefits of detached objects?

Ques 7. What are the pros and cons of detached objects?

Ques 8. What is the difference between the session.get() method and the session.load() method?

Ques 9. How would you reatach detached objects to a session when the same object has already been loaded into the session?

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