before(): call(* set*(..)) {
System.out.println("A setter method was called.");
}.webp){kind=logo}
Ask the right questions to secure the right AspectJ talent among an increasingly shrinking pool of talent.
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.
The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.
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.
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.
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.
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.
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.
A candidate's technical skills are important, but so is their ability to fit into the existing team culture. They should be able to work well with others and contribute positively to the team dynamic.
AspectJ is used for AOP, so they should understand the concepts and principles of AOP, and how to apply them effectively in development.
Communication is key in a team-based development environment. They need to be able to explain their ideas and solutions clearly to both technical and non-technical team members.
AspectJ is an extension of Java, so understanding Java and related technologies is important. This will ensure they can work effectively within the technology stack.
Problem-solving skills are critical in any development role. The candidate should be able to explain their thought process when tackling complex problems.
This is crucial as AspectJ is the main language they will be using for development. They should be able to demonstrate their knowledge and understanding of the language.
The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.
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.
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.
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.
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.
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.
At this point, the candidate should demonstrate a deep understanding of AspectJ programming language. They should be proficient in coding, debugging, and integrating AspectJ into Java applications. They should also show strong problem solving skills. Red flags include lack of practical experience or inability to apply theoretical knowledge.
before(): call(* set*(..)) {
System.out.println("A setter method was called.");
}before(): execution(* com.example..*(..)) {
System.out.println(thisJoinPoint);
}pointcut update(): call(* java.util.List+.add*(..));
after() returning: update() {
System.out.println("An element was added to the list.");
}void around(): call(* *.run()) {
System.out.println("Before running.");
proceed();
System.out.println("After running.");
}declare parents: com.example.MyClass implements java.io.Serializable;pointcut singleton(): within(com.example.Singleton+);
before(): singleton() && !cflowbelow(execution(* com.example.Singleton+.new(..))) {
throw new RuntimeException("Singleton violation");
}The final few interview questions for a AspectJ candidate should typically focus on a combination of technical skills, personal goals, growth potential, team dynamics, and company culture.
Best practices for using AspectJ in large-scale projects include keeping aspects as small and focused as possible, using a consistent naming convention for aspects and pointcuts, thoroughly testing aspect code, and documenting the purpose and behavior of each aspect.
Performance of AspectJ applications can be optimized by minimizing the number of join points, using compile-time weaving instead of load-time weaving, and avoiding complex pointcut expressions. It's also important to measure the performance impact of aspects and optimize them as necessary.
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.
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.
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.
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