Enterprise Java Beans (EJBs) Interview Questions blogis integral to the Java EE platform for building complex, distributed applications at scale.

EJB is especially vital to component-based designs, facilitating easy reuse, maintainability, and system integration.

Thus, Java developers working on corporate apps must possess an in-depth knowledge of EJB fundamentals to answer interview questions confidently.

This blog article covers some key EJB topics with interview questions and their answers.

These questions assess your knowledge of EJB technology, its components and architectural patterns for business applications using Java Beans (EJB).

You’ll come out ahead by answering them carefully before an interview and reviewing this material. Plus, you will gain more insights into the applications of EJB technology!

1. What is an Enterprise Java Bean (EJB)?
An EJB is an Enterprise Java Bean that handles business logic and data transformation.

2. How are staple beans created, and what are they used for?

Staple beans are created every time a JDI lookup or dependency injection is performed.

They ensure that the same bean instance is provided throughout the application.

3. How are Singleton beans generally created, and what loading strategies can the container adopt?

Singleton beans are generally created by the container at application load.

The container can adopt an eager or lazy load strategy for singleton beans.

4. What happens when the container destroys a bean, and why is this process necessary?

When a bean is destroyed, the container will create a new instance from scratch.

This is important because developers should clean up after themselves, even though there is a garbage collection mechanism behind the scenes.

5. How do stateless and stateful beans differ regarding lifecycle and mapping?

Stateless beans do not maintain a state between method calls and are shared across multiple sites.

Stateful beans maintain a condition between method calls and always have a one-to-one mapping, with one bean per instance.

6. What are the two primary lifecycle transitions a stateful bean goes through, and why are they important?

A stateful bean goes through two primary lifecycle transitions: post-construct and destroy.

They are essential because they allow the bean to perform necessary actions before and after executing the business methods.

7. When is the post-construct method invoked in the lifecycle of a stateful bean, and why is it important?

The post-construct method is invoked after the constructor completes, assuming no exceptions were generated.

It is essential because it allows the bean to perform necessary actions before executing business methods, such as initialising resources and dependencies.

8. What is the purpose of the specific method created in the EJB2.x world?

The specific method created in the EJB2.x world was to implement a naming convention starting with the three letters EJB, all lowercase letters and then the fourth letter uppercase.

However, this made the model brittle as there was no interface to implement for compile-time checks physically.

9. What is the purpose of the idea in EJB3.0?

The idea in EJB3.0 was to move everything to annotations or as much as possible to annotations.

Method signatures could be public, private, or protected.

10. What is the purpose of creating a public method?

Creating a public method is a dual-purpose method.

The container can use the method as a callback and perform business operations.

For example, the singleton beam has two methods that function as lifecycle callbacks.

11. What are the names of the two methods that function as lifecycle callbacks in the singleton beam?

The two methods that function as lifecycle callbacks in the singleton beam are Post-construct.

12. What is the access modifier of these two methods?

The access modifier of these two methods is denoted as private.

13. What is the purpose of the pre-destroy annotation?

The container notifies the shaft before an application is unloaded through the destroy annotation.

It is essential to ensure the code is robust enough not to throw an exception, as having both would make no sense.

Instead, define a local interface and tag an interface with local when implementing the bean.

Some inheriting, some remote, some local, all inherit the same interface.

14. What is the purpose of defining a local interface and tagging an interface with local when implementing the bean?

Defining a local interface and tagging an interface with local when implementing the bean is essential to ensure the code is robust enough not to throw an exception.

This approach allows developers to define a set of methods the bean must implement, providing consistency across all beans that implement the same interface.

15. What is the purpose of the lifecycle in EJB beans?

The lifecycle in EJB beans involves understanding how a bean transitions from its existence through the destruction phase and how developers can get notifications from the container as it goes through those transitions.

16. What are the three types of beans in the EJB world?

The three types of beans in the EJB world are stateless, stateful, and singleton.

17. What is the difference between an eager and lazy load strategy for singleton beans?

An eager load strategy creates the singletons directly on application initialisation, while a lazy load strategy determines when to build the singleton based on run time.

18. What should developers do during the initialisation process before demolition?

Developers should de-initialize their initialisations during the initialisation process before demolition.

19. What are the two primary lifecycle transitions for the stateless bean?

The two primary lifecycle transitions for the stateless bean are post-construct and destroy.

20. What is the purpose of the destroy method in the stateless bean?

The destroy method is invoked before the object is destroyed or the finalised plan is executed.

21. What is the purpose of the pre-passivate and step methods in the stateless bean?

The steps methods are used to support load by reusing things.

22. How can developers physically tell the container when to remove an instance of a stateless bean?

Developers can physically tell the container when to remove an instance of a stateless bean by annotating a method with the remove annotation.

23. What are the three types of state charts in the EJB world?

The EJB world’s three types of state charts are stateful, stateless, and singleton.

24. What was the issue with the naming convention used in the EJB2.x world?

In the EJB2.x world, a specific method was created with a naming convention that started with the three letters EJB, all lowercase, and then the fourth letter uppercase.

However, this made the model brittle as there was no interface to implement for compile-time checks physically.

25. How was the idea implemented in EJB3.0?

In EJB3.0, the idea was to move everything to annotations or as much as possible.

This allowed for using any method signature and name, whether public, private, or protected.

26. What is the purpose of the post-construct method in the singleton bean?

The post-construct method creates an instance variable, and calls add through the divide.

27. What is the purpose of the destroy method in the singleton bean?

The destroy method is invoked before the application is unloaded.

28. What is the purpose of stacking multiple annotations?

Stacking multiple annotations allows for adding various lifecycle callback annotations to a single method without requiring a one-to-one relationship.

29. What are message-driven beans?

Message-driven beans are used to create reusable workflows in programming.

30. How are EJB Stateless Beans managed and shared across multiple sites?

EJB Stateless beans are shared across multiple sites, and the container will create a stateless bean if it doesn’t exist.

The container may create a secondary bean if threaded access is an issue.

31. How do business rules fit into an n-layer architecture?

Business rules are implemented in the orange layer of an n-layer architecture, which is responsible for handling and executing business logic or rules.

32. What are design-by-contract technologies?

Design-by-contract technologies are used in the orange layer of an n-layer architecture to execute business logic or rules.

They involve using interfaces to define the behaviour of the business logic.

33. What is a business object?

A business object is a Java Bean with properties and methods, such as adding an item to a cart or discussing the capacity and price of the cart, and is used in the business area.

34. How do Java Beans help businesses handle and execute business logic and rules?

Java Beans helps businesses handle and execute business logic and rules by incorporating design-by-contract technologies and interfaces, which create a consistent decision-making process and adhere to legal requirements and capacities.

35. What is the Enterprise Java Bean’s EJBs Purpose? 

The EJB is the business logic of an application, which fulfils the purpose of the application and does not perform any data display or direct communication with the database.

36. What is the role of the container in an EJB?

The container is responsible for registering the object, providing remote interfaces, creating and destroying it as necessary, checking for security, and managing its state.

37. Which role of interfaces in Java?

Interfaces work in Java by providing a list of properties and methodsan object must implement.

38. What is the difference between a stateful, entity, and message-driven EJB?

Stateful beans maintain the state or information about the client across multiple requests, and entity beans represent the state of an object.

They can be persisted in a database, and message-driven beans are triggered by messages and perform specific tasks.

Let us get into the important Multiple-choice questions on this platform!!!

1. What happens when the EJB Stateless beans are shared across multiple sites?

Creates a new stateless bean every time it is accessed✔️
Reuses an existing stateless bean
Creates a secondary stateless bean if it can’t reuse the pre-existing bean
Destroys the stateless bean after it is accessed

2. What happens to Staple beans?

They are created every time a JDI lookup or dependency injection is performed ✔️
Ended after they are created
They go through post-construct and destroy lifecycle transitions
The container reuses them

3. What does EJB stand for?

Enterprise Java Bean ✔️
Enterprise Java Book
Enterprise Java Basic
Enterprise Java Byte

4. What is an Enterprise Java Bean?

A means of dividing EJB components into categories
A type of EJB that maintains the state for one client
A component used in enterprise applications ✔️
A type of EJB that does not maintain a conversational state with the client

5. What is the only bean that goes through all five life cycle transitions?

Stateless
Staple
Singleton
Stateful ✔️

6. When is the post-construct method invoked?

After the constructor completes ✔️
After the bean is destroyed
Before the constructor is called
After the business methods are executed

7. Where is Enterprise Java Bean commonly used?

In web applications
In desktop applications
In enterprise applications ✔️
In mobile applications

8. Which of the following is an example of an Enterprise Java Bean?

JSP
Servlet
Entity Bean
JDBC ✔️

9. What is the purpose of Enterprise Java Bean?

To create, retrieve, update, and delete records in a database
To maintain the state or information about the client across multiple requests
To represent a single database table
To encapsulate the business logic of an application ✔️

10. What is the purpose of the access modifier denoted as private in the text?

Make the methods visible to the caller
Allow the container to perform business operations on the methods
To make the methods hidden from the caller but still available to the container ✔️
Prevent the methods from being called by the container

The EJB Interview Questions blog offers an all-inclusive solution to successful discussions focusing on EJB containers, enterprise beans and component-based design.

Java developers building corporate apps must understand these ideas to use EJB effectively, as this knowledge will assist with developing large-scale, distributed applications with scalability features.

Our interview questions for EJB may help you learn this technology and navigate obstacles when developing such large apps.

Thanks again, and have a fantastic day!!!!!