Cross-cutting concerns concept in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Cross-cutting Concerns in Spring Boot

Which of the following best describes a cross-cutting concern in a Spring Boot application?

A A UI component that handles user input.

B A feature that affects multiple parts of the application, like logging or security, implemented separately from business logic.

C A database entity that stores user information.

D A specific business rule applied only in one service class.

💡 Hint

Think about features that are needed across many parts of the app, not just one place.

Cross-cutting concerns are aspects like logging, security, or transaction management that affect many parts of an application. Spring Boot uses AOP to separate these from core business logic.

❓ component_behavior

intermediate

Behavior of Aspect in Spring Boot

Given a Spring Boot aspect that logs method execution time, what will happen when a method annotated with @LogExecutionTime is called?

Spring Boot

@Aspect
@Component
public class LoggingAspect {
    @Around("@annotation(com.example.LogExecutionTime)")
    public Object logTime(ProceedingJoinPoint joinPoint) throws Throwable {
        long start = System.currentTimeMillis();
        Object proceed = joinPoint.proceed();
        long executionTime = System.currentTimeMillis() - start;
        System.out.println(joinPoint.getSignature() + " executed in " + executionTime + "ms");
        return proceed;
    }
}

A The method runs twice because of the aspect.

B The method is skipped and only the execution time is printed.

C The method throws a runtime exception due to missing annotation.

D The method runs normally and its execution time is printed to the console.

💡 Hint

The aspect wraps the method to measure time but does not prevent execution.

The @Around advice runs code before and after the method. It calls proceed() to run the method and then logs the time.

📝 Syntax

advanced

Correct Syntax for Defining a Pointcut

Which option correctly defines a pointcut that matches all methods in the package com.example.service and its subpackages?

A @Pointcut("execution(* com.example.service..*(..))")

B @Pointcut("execution(* com.example.service.*(..))")

C @Pointcut("execution(* com.example..service.*(..))")

D @Pointcut("execution(* com.example.service.*.*(..))")

💡 Hint

Use '..' to include subpackages in pointcut expressions.

The '..' in the expression means any subpackage depth. Option A matches all methods in com.example.service and its subpackages.

🔧 Debug

advanced

Identifying the Cause of Aspect Not Triggering

A developer created an aspect to log method calls but notices it never runs. Which of the following is the most likely cause?

A The aspect class is not annotated with @Component or not scanned by Spring.

B The application is missing a database connection.

C The method being called is private.

D The method has no parameters.

💡 Hint

Spring needs to know about the aspect bean to apply it.

For Spring AOP to work, the aspect must be a Spring bean, typically annotated with @Component and scanned by Spring. Otherwise, it won't be applied.

❓ state_output

expert

Output of Logging Aspect with Multiple Method Calls

Given the following Spring Boot aspect and service, what will be printed to the console when main() calls service.process() twice?

Spring Boot

public class Service {
    @LogExecutionTime
    public void process() throws InterruptedException {
        Thread.sleep(100);
    }
}

public class Main {
    public static void main(String[] args) throws InterruptedException {
        Service service = new Service();
        service.process();
        service.process();
    }
}

@Aspect
@Component
public class LoggingAspect {
    @Around("@annotation(com.example.LogExecutionTime)")
    public Object logTime(ProceedingJoinPoint joinPoint) throws Throwable {
        long start = System.currentTimeMillis();
        Object proceed = joinPoint.proceed();
        long time = System.currentTimeMillis() - start;
        System.out.println(joinPoint.getSignature() + " executed in " + time + "ms");
        return proceed;
    }
}

A Compilation error due to missing annotations on Service class.

B Two lines printed showing execution time for each process() call.

C No output because the aspect is not applied to the service instance created with new.

D One line printed showing execution time for the first call only.

💡 Hint

Spring AOP works only on Spring-managed beans, not on objects created with new.

The service instance is created manually with new, so Spring does not manage it and the aspect is not applied. No logging output appears.