@Aspect annotation in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output when an @Aspect logs method execution time?

Consider an @Aspect that logs the execution time of a method annotated with @Timed. What will be printed when the method runs?

Spring Boot

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class TimingAspect {
    @Around("@annotation(Timed)")
    public Object logExecutionTime(ProceedingJoinPoint joinPoint) throws Throwable {
        long start = System.currentTimeMillis();
        Object proceed = joinPoint.proceed();
        long duration = System.currentTimeMillis() - start;
        System.out.println("Execution time: " + duration + "ms");
        return proceed;
    }
}

// Assume a method annotated with @Timed is called and takes 50ms to execute.

A Execution time: 50ms

B No output printed

C Execution time: 0ms

D Compilation error due to missing @Timed annotation definition

💡 Hint

Think about what the @Around advice does and when the print statement runs.

The @Around advice wraps the method call, measuring time before and after execution. It prints the actual duration, so if the method takes 50ms, it prints 'Execution time: 50ms'.

📝 Syntax

intermediate

Which @Aspect syntax correctly matches all methods in a package?

You want an @Aspect to intercept all methods in the package com.example.service. Which pointcut expression is correct?

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

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

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

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

💡 Hint

Remember '..' means recursive subpackages and '*' means any class or method name.

The expression 'execution(* com.example.service..*(..))' matches any method in com.example.service and its subpackages. Option C matches only methods in classes directly in com.example.service package, not subpackages. Option C ('within(com.example.service.*)') matches method executions in classes directly in the package using within, not subpackages. Option C is incorrect because the declaring type pattern 'com.example.service.*.*' is invalid syntax.

❓ lifecycle

advanced

When is an @Aspect bean initialized in Spring Boot lifecycle?

At what point in the Spring Boot application lifecycle is an @Aspect bean created and ready to intercept method calls?

A During Spring context startup, alongside other singleton beans before application runs

B After all singleton beans are created and the context is fully initialized

C During Spring context startup, before any other beans are created

D Only when the first advised method is called at runtime

💡 Hint

Think about when Spring creates singleton beans and how proxies are applied.

Spring creates @Aspect beans as singleton beans during context startup, alongside other singleton beans. The proxies for advised beans are created then, so aspects are ready before application logic runs.

🔧 Debug

advanced

Why does this @Aspect advice not run for a self-invoked method?

Given this code, why does the @Aspect advice not trigger when methodA calls methodB inside the same class? public class MyService { @MyAdvice public void methodA() { methodB(); } @MyAdvice public void methodB() { // do something } }

A The @MyAdvice annotation is not recognized by Spring AOP

B The aspect is not registered as a Spring bean

C methodB is private and cannot be proxied

D Spring AOP proxies only intercept external method calls, not self-invocations

💡 Hint

Think about how Spring AOP creates proxies and what calls they intercept.

Spring AOP uses proxies that intercept calls from outside the bean. Internal calls like methodA calling methodB directly do not go through the proxy, so advice on methodB is not triggered.

🧠 Conceptual

expert

What is the effect of @Aspect precedence with @Order annotation?

You have two @Aspect classes with @Order(1) and @Order(2). Which advice runs first when both apply to the same method?

A The aspect with @Order(2) runs before the one with @Order(1)

B The aspect with @Order(1) runs before the one with @Order(2)

C Order does not affect execution sequence of aspects

D Both aspects run simultaneously in no guaranteed order

💡 Hint

Lower @Order values have higher precedence in Spring AOP.

In Spring AOP, aspects with lower @Order values have higher precedence and their advice runs first. So @Order(1) runs before @Order(2).