AOP for logging in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding AOP Pointcut Expressions

Which pointcut expression correctly matches all methods in classes within the package com.example.service and its subpackages?

A within(com.example.service.*)

B execution(* com.example.service.*(..))

C execution(* com.example.service..*(..))

D execution(* com.example.service..*.*(..))

💡 Hint

Remember that .. matches subpackages and any number of arguments.

The expression execution(* com.example.service..*(..)) matches all methods in com.example.service and any subpackage. Option C matches only classes directly in service package, not subpackages. Option C matches only classes directly in service package but not methods. Option C uses invalid syntax **.

💻 Command Output

intermediate

Output of Logging Aspect Around Advice

Given the following Spring AOP around advice, what will be printed when the method processOrder() is called?

Spring Boot

public Object logAround(ProceedingJoinPoint joinPoint) throws Throwable {
    System.out.println("Start: " + joinPoint.getSignature().getName());
    Object result = joinPoint.proceed();
    System.out.println("End: " + joinPoint.getSignature().getName());
    return result;
}

A Start: processOrder\nEnd: processOrder

B Start: processOrder

C End: processOrder\nStart: processOrder

D End: processOrder

💡 Hint

Think about the order of statements before and after proceed().

The advice prints "Start" before calling the actual method with proceed(), then prints "End" after the method completes. So the output is "Start: processOrder" followed by "End: processOrder".

❓ Configuration

advanced

Correct Aspect Configuration for Logging

Which of the following Spring configuration snippets correctly enables AspectJ auto-proxying and declares a logging aspect bean?

A @Configuration\n@ComponentScan(basePackages = "com.example")\npublic class AppConfig {\n}

B @Configuration\n@EnableAspectJAutoProxy\npublic class AppConfig {\n @Bean\n public LoggingAspect loggingAspect() {\n return new LoggingAspect();\n }\n}

C @EnableAspectJAutoProxy\n@Component\npublic class LoggingAspect {}

D @Configuration\n@EnableTransactionManagement\npublic class AppConfig {\n @Bean\n public LoggingAspect loggingAspect() {\n return new LoggingAspect();\n }\n}

💡 Hint

Enabling AspectJ auto-proxying is required for aspects to work.

Option B correctly uses @EnableAspectJAutoProxy and declares the aspect bean. Option B misses enabling AOP. Option B misses configuration class and bean declaration. Option B enables transaction management, not AOP.

❓ Troubleshoot

advanced

Diagnosing Missing Logs from Aspect

A developer created a logging aspect with @Around advice but no logs appear when methods run. What is the most likely cause?

A The aspect class is not annotated with <code>@Aspect</code>

B The methods being called are private

C The logging statements use <code>System.out.println</code> instead of a logger

D The application is missing <code>spring-boot-starter-web</code> dependency

💡 Hint

Check if the aspect is recognized by Spring AOP.

Without @Aspect annotation, Spring does not recognize the class as an aspect, so advice is not applied. Private methods are not proxied by Spring AOP, but that alone doesn't prevent logs if public methods are called. Using System.out.println still prints output. Missing web starter does not affect AOP.

✅ Best Practice

expert

Choosing the Best Advice Type for Logging Execution Time

Which advice type is best suited to measure and log the execution time of a method in Spring AOP?

A @Before advice, because it runs before the method starts

B @AfterReturning advice, because it runs after method returns successfully

C @AfterThrowing advice, because it runs if the method throws an exception

D @Around advice, because it can run code before and after method execution

💡 Hint

Think about needing to capture time before and after the method runs.

@Around advice wraps the method call, allowing code to run before and after the method. This lets you record start time before and end time after, calculating execution duration. Other advice types run only before or after, not both.