7 Spring AOP Interview Questions (With Example Answers)

Updated 13 October 2022

Aspect-oriented programming (AOP) is a programming paradigm that complements object-oriented programming (OOP). Spring AOP is a popular Java framework that helps programmers build aspect-oriented, flexible web applications in Java. Preparing for questions on aspect-oriented programming and the Spring AOP framework can help you perform well in interviews and build a successful career as a Java developer. In this article, we list a few Spring AOP interview questions, discuss why interviewers ask these, share sample responses and tips to help you prepare for an upcoming Java technical interview.

Spring AOP Interview Questions With Sample Answers

Here are a few Spring AOP interview questions and sample responses that you can use as inspiration while preparing for an interview:

1. How would you explain object-oriented and aspect-oriented programming to a five-year-old?

Hiring managers usually begin the interview with explanatory questions like these to test your knowledge of the foundational principles of the Spring AOP framework. When the interviewer asks you to explain a concept or feature to a child, they would like you to explain it in basic terms so that even non-technical people can understand it. The easiest way to explain programming concepts like AOP and OOP in simple terms is by using real-life examples. This question is an excellent opportunity to showcase your clear and concise communication skills to the employer.

Example: 'Let us consider a car. Each car has a unique model name, manufacturing year, engine size and other distinct features. In OOP, we define a class for a car. All cars would use this class but with varying attributes. For example, a blue car has the colour attribute blue, while a red car has the colour attribute red. In aspect-oriented programming, we organise code around behaviours instead of attributes and classes. Known as aspects or concerns, these behaviours are separate from one another and help increase modularity by crosscutting concerns.'

2. What are the benefits and limitations of working with Spring AOP?

The interviewer might ask this question to make sure you can clearly describe the benefits of the Spring AOP framework and are aware of its limitations. In your response, you can provide a few advantages of using Spring AOP and complete it by explaining any difficulties you have experienced with the framework in your previous roles.

Example: 'I think the biggest benefit of using the Spring AOP framework is that it is easy to configure. As it runs pure Java, we do not require a separate compilation unit or separate class loader. It offers other benefits, like integrating crosscutting concerns into the classes and creating aspects using @aspetJ or XML annotations. Coming to the limitations, I have noticed that debugging code in the AOP framework is time-consuming. Also, aspects cannot advise other aspects. This is because, once we mark a class as an aspect, the Spring framework prevents it from getting auto-proxied.'

3. What are the differences between pointcut and join point in Spring AOP?

Pointcut and joint point are two core terminologies in the Spring AOP framework. The interviewer might ask this question to ensure that you know what each does and how they are different. To answer this question, you can begin by defining pointcut and join point and then explain their differences using examples.

Example: 'A join point is a step in the program or application where you apply the AOP aspect. It can also be a specific advice execution instance. For example, it can be an execution handling, method execution or a change in the object variable's value. In the Spring framework, a join point always denotes a method execution. A pointcut is an expression that uses one or more join points to give advice. You can define a pointcut using patterns or expressions. For example, if a point cut chooses two join points, it has two expressions.'

4. What type of weaving does Spring AOP use?

The interviewer asks this two-part question to test your knowledge about weaving in AOP and evaluate if you know the specific weaving feature used in Spring AOP. In the first section of your answer, you can provide a brief overview of the three types of weaving in AOP. In the next section, you can explain the weaving type in Spring AOP and its working.

Example: 'There are three types of weaving in AOP, including compile-time, post-compile and load-time weaving. Spring AOP makes use of runtime weaving, also known as load-time weaving. In runtime weaving, the proxies of the targeted object weave the aspects during the application's execution using dynamic, JDK or CGLIB proxies.'

5. How to enable advice in Spring AOP?

Advice is the action an aspect takes at a particular join point. There are different types of advice in Spring AOP, including around, before and after. The interviewer might ask questions like these to evaluate your practical knowledge in Spring AOP. You can frame your answer by explaining the steps to enable an advice.

Example: 'To enable advice in Spring, you can use the annotations available in AspectJ. Before executing this step, ensure that you implement the @EnableAspectJAutoProxy annotation to the configuration class. This ensures that Spring AOP can handle components denoted with AspectJ's annotations.'

6. Which do you prefer: AspectJ or Spring AOP?

AspectJ and Spring are the two popular frameworks for implementing aspect-oriented programming. The interviewer might ask this question to evaluate if you understand the pros and cons of both these frameworks so that you can choose the right one to work with, depending on the requirements. In your response, you can take a balanced approach by highlighting the benefits of both frameworks and sharing use cases for each.

Example: 'I prefer Spring AOP, as it is easier to use than AspectJ. In Spring AOP, we do not consider the intricacies of weaving. Also, a programmer familiar with AspectJ can easily migrate to Spring since the latter supports the annotations available in AspectJ. A limitation of Spring AOP is that it applies only to the beans created in the Spring framework. Spring supports only proxy-based AOP, while AspectJ supports all pointcuts. By analysing all the pros and cons, we can understand that both frameworks have their benefits and the right choice depends on the project requirements.'

7. What are the types of advice supported in Spring AOP?

Advice is the implementation of crosscutting concerns. To answer this question, you can explain the five types of advice in Spring AOP with a brief description of each. Revising the basic concepts of AOP can help you answer similar theoretical questions confidently.

Example: 'There are five types of advice in the Spring AOP framework. They are before, after returning, after throwing, after and around advice. The before advice executes before a join point, but it cannot prevent execution flow unless it throws an exception. The after-returning advice executes after a joint point finishes normally. The after-throwing advice executes if a method exits by throwing an exception. The after advice executes irrespective of how the join point exits. The around is the most powerful advice and surrounds a join point using a method invocation.'

Tips To Prepare For A Spring AOP Interview

Preparing for the interview can help showcase your professionalism and technological savvy. Here are a few tips to help you do well in an upcoming technical interview:

Research the job and company. Read the job description carefully to identify the role's responsibilities and prepare to showcase your relevant skills and experiences. Understand the company culture and organisational structure to get an idea of what they are looking for in an employee.
Demonstrate your coding skills. Sometimes the hiring panel might ask you to write algorithms or code snippets during the interview. Reviewing common coding questions and being prepared for them can help you remain confident and at ease during the hiring process.
Do not memorise answers. Remember to showcase your personality and experiences in your answers. Avoid rote learning answers, as it can make your responses feel robotic and disinterested.
Revise the basics. While the interviewer does not expect you to know everything about Spring AOP, it is essential to revise the basics and foundational principles so that you can use them to answer challenging questions.
Showcase your previous experiences. This helps to distinguish your profile from other candidates, establishing you as a knowledgeable and experienced professional. You can use the STAR interview response technique to make your answers relevant while highlighting your skills and experiences.

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