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AspectJ is a computer programming language that extends Java to provide aspect-oriented programming capabilities. Developed by Xerox Palo Alto Research Center (PARC) in the late 1990s, it introduces new constructs such as pointcuts, advice, and aspects to modularize cross-cutting concerns in software development. The Eclipse Foundation later took over its management and continues its development today. AspectJ has been influential in the field of software engineering, inspiring similar features in other languages like Spring AOP for Java. Its design principles and implementation are well-documented through numerous academic papers and technical reports from PARC.

Ask the right questions secure the right AspectJ talent among an increasingly shrinking pool of talent.

First 20 minutes

General AspectJ app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in AspectJ application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you explain the concept of crosscutting concerns in AspectJ?

Crosscutting concerns are parts of a program that affect other parts. They occur when a single change affects multiple classes. AspectJ handles these concerns by modularizing them.

What are the main components of AspectJ?

The main components of AspectJ are aspects, join points, pointcuts, and advice. Aspects are classes that encapsulate crosscutting concerns. Join points are points in the program flow where crosscutting concerns intersect with base code. Pointcuts define collections of join points, and advice are actions taken by aspects at a particular join point.

Describe the difference between before advice and after advice in AspectJ.

Before advice in AspectJ is executed before the join point method, whereas after advice is executed after the join point method. The after advice can be further divided into after returning advice, after throwing advice, and after (finally) advice.

How would you use pointcuts to specify when to execute an aspect?

Pointcuts are used in AspectJ to define a collection of join points. You can use pointcut expressions to specify when an aspect should be executed. For example, 'execution(* com.example..*(..))' specifies that the aspect should be executed for any method in the 'com.example' package.

What is the role of the AspectJ weaver?

The AspectJ weaver is responsible for weaving aspects into the Java bytecode. It modifies the bytecode of the classes to include the aspect code at the appropriate join points.

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What you’re looking for early on

Does the candidate have a solid understanding of AspectJ language?

Has the candidate demonstrated ability to solve complex problems?

Does the candidate have experience with Java and other relevant technologies?

Is the candidate able to articulate their thought process clearly?

Next 20 minutes

Specific AspectJ development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

How would you handle exceptions in AspectJ?

Exceptions in AspectJ can be handled using the after throwing advice. This advice is executed when a join point throws an exception. You can specify the type of exception to catch in the pointcut expression.

What are the differences between AspectJ and Spring AOP?

AspectJ is a full-featured aspect-oriented programming framework, whereas Spring AOP is a lighter version that integrates with the Spring framework. AspectJ supports all AOP concepts, while Spring AOP only supports method execution join points. AspectJ weaves aspects at compile time, while Spring AOP does it at runtime.

How would you use AspectJ to log method execution times?

You can use AspectJ to log method execution times by creating an aspect with around advice. The around advice can measure the time before and after the method execution, and then log the difference.

What are the limitations of AspectJ?

Some limitations of AspectJ include the complexity of pointcut expressions, the difficulty in debugging aspect code, and the potential for unexpected side effects due to the modification of bytecode.

How would you use AspectJ for transaction management?

You can use AspectJ for transaction management by creating an aspect with around advice. The around advice can start a transaction before the method execution, commit the transaction if the method completes successfully, or roll back the transaction if an exception is thrown.

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At this point, a skilled AspectJ engineer should demonstrate strong problem-solving abilities, proficiency in AspectJ programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with AspectJ.

What does the following AspectJ code do?
before(): call(* set*(..)) {
  System.out.println("A setter method was called.");
}
This is an AspectJ advice. It intercepts all calls to any setter methods (methods starting with 'set') and prints 'A setter method was called.' before the actual method execution.
What will be the output of the following AspectJ code?
before(): execution(* com.example..*(..)) {
  System.out.println(thisJoinPoint);
}
This is an AspectJ advice that intercepts all method executions within the 'com.example' package and its sub-packages. It prints the join point's details, which includes the method signature and the type of the join point.
What does the following AspectJ code do?
pointcut update(): call(* java.util.List+.add*(..));
after() returning: update() {
  System.out.println("An element was added to the list.");
}
This AspectJ code defines a pointcut named 'update' which captures calls to any 'add' methods of List interface and its subclasses. It then defines an advice that gets executed after the 'add' method returns successfully, printing 'An element was added to the list.'
What does the following AspectJ code do?
void around(): call(* *.run()) {
  System.out.println("Before running.");
  proceed();
  System.out.println("After running.");
}
This AspectJ code defines an around advice for the 'run' method of any class. It prints 'Before running.' before the 'run' method is executed, executes the 'run' method, and then prints 'After running.' after the 'run' method has finished.

Wrap-up questions

Final candidate for AspectJ Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle AspectJ application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the differences between static and dynamic crosscutting in AspectJ?

Static crosscutting in AspectJ involves modifying the static structure of a program, such as adding fields or methods to a class. Dynamic crosscutting involves modifying the behavior of a program, such as changing the execution of a method.

How would you test aspect code in AspectJ?

Testing aspect code in AspectJ can be challenging because aspects affect the behavior of the base code. One approach is to use a testing framework that supports AspectJ, such as AspectJ Testing Framework (ajtf). Another approach is to design the aspects to be as decoupled as possible from the base code, and then test them independently.

What are the differences between compile-time and load-time weaving in AspectJ?

Compile-time weaving in AspectJ involves weaving aspects into the bytecode at compile time. This requires the AspectJ compiler. Load-time weaving involves weaving aspects into the bytecode when the classes are loaded into the JVM. This requires the AspectJ weaver and a special class loader.

AspectJ application related

Product Perfect's AspectJ development capabilities

Beyond hiring for your AspectJ engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in AspectJ projects, and can engage in multiple capacities.

AspectJ Consultive assessments

AspectJ Application Conversion Assessment AspectJ Application Integration Assessment AspectJ Data & Database Integration Assessment

Custom AspectJ development projects

Custom AspectJ App Conversion AspectJ Custom App Development Process App UI Design for AspectJ Facelifts

Hiring guide for AspectJ Engineers

AspectJ Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the AspectJ engineer at this point.

AspectJ Consultive assessments

Custom AspectJ development projects