@Around advice for full control in Spring Boot - Mini Project: Build & Apply

Using @Around Advice for Full Control in Spring Boot

📖 Scenario: You are building a Spring Boot application where you want to log method execution time and control the method execution flow.

🎯 Goal: Create an @Around advice in a Spring Boot aspect to measure and log the execution time of a service method, and control when the method runs.

📋 What You'll Learn

Create a Spring Boot service class with a method performTask() that returns a string.

Create an aspect class with an @Around advice method.

Use ProceedingJoinPoint to control the method execution inside the advice.

Log the start time, execute the method, log the end time, and calculate the duration.

Return the original method's result from the advice.

💡 Why This Matters

🌍 Real World

Using @Around advice in Spring Boot helps monitor and control method execution, useful for logging, performance measurement, and adding custom behavior around business logic.

💼 Career

Understanding @Around advice is important for backend developers working with Spring Boot to implement cross-cutting concerns like logging, security, and transactions.

1

Create the Service Class with performTask() Method

Create a Spring service class called TaskService with a public method performTask() that returns the string "Task Completed".

Spring Boot

import org.springframework.stereotype.Service;

@Service
public class TaskService {
    // Your code here
}

Hint

Use @Service annotation and create a method that returns the exact string.

2

Create the Aspect Class with @Around Advice Method

Create an aspect class called LoggingAspect annotated with @Aspect and @Component. Inside it, declare a method logExecutionTime with @Around advice targeting performTask() method in TaskService. The method should accept a ProceedingJoinPoint parameter.

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 LoggingAspect {
    // Your code here
}

Hint

Use @Around with the pointcut expression for performTask() and accept ProceedingJoinPoint as parameter.

3

Add Timing Logic Inside the @Around Advice

Inside the logExecutionTime method, record the start time using System.currentTimeMillis(). Then call joinPoint.proceed() to execute the original method and store its result. After that, record the end time and calculate the duration by subtracting start time from end time. Finally, print the duration using System.out.println and return the original method's result.

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 LoggingAspect {
    @Around("execution(* TaskService.performTask(..))")
    public Object logExecutionTime(ProceedingJoinPoint joinPoint) throws Throwable {
        // Your code here
    }
}

Hint

Use System.currentTimeMillis() before and after proceed() to measure time, then print and return the result.

4

Complete the Aspect to Fully Control Method Execution

Modify the logExecutionTime method to add a print statement before calling joinPoint.proceed() that prints "Starting method execution". Also add a print statement after joinPoint.proceed() that prints "Method execution finished". This shows full control over when the method runs inside the advice.

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 LoggingAspect {
    @Around("execution(* TaskService.performTask(..))")
    public Object logExecutionTime(ProceedingJoinPoint joinPoint) throws Throwable {
        // Your code here
    }
}

Hint

Print messages before and after proceed() to show control over method execution.

Practice

1. What is the main purpose of using @Around advice in Spring AOP?

easy

A. To run code before and after a method, controlling its execution fully

B. To only run code after a method finishes

C. To replace the method with a new implementation without calling the original

D. To log method parameters without affecting execution

Solution

1. Step 1: Understand the role of @Around advice

   @Around advice wraps a method, allowing code to run before and after the method execution.

2. Step 2: Compare options with this behavior

   Only To run code before and after a method, controlling its execution fully describes full control before and after the method, matching @Around's purpose.

3. Final Answer:

   To run code before and after a method, controlling its execution fully -> Option A

4. Quick Check:

   @Around advice = full control before and after method [OK]

Hint: Remember @Around wraps method execution fully [OK]

Common Mistakes:

• Thinking @Around only runs after method
• Confusing @Around with @After or @Before
• Forgetting @Around can modify inputs and outputs

2. Which of the following is the correct way to proceed with the original method inside an @Around advice method?

easy

A. return joinPoint.proceed();

B. joinPoint.execute();

C. proceed(joinPoint);

D. joinPoint.run();

Solution

1. Step 1: Recall the method to call original execution

   In @Around advice, the original method is executed by calling joinPoint.proceed().

2. Step 2: Match the correct syntax

   Only return joinPoint.proceed(); uses the correct method name and syntax to proceed.

3. Final Answer:

   return joinPoint.proceed(); -> Option A

4. Quick Check:

   Call original method with joinPoint.proceed() [OK]

Hint: Use joinPoint.proceed() to run original method [OK]

Common Mistakes:

• Using incorrect method names like execute() or run()
• Forgetting to return the result of proceed()
• Calling proceed() without parentheses

3. Given the following @Around advice code, what will be printed when someMethod() returns "Hello"?

@Around("execution(* someMethod())")
public Object aroundAdvice(ProceedingJoinPoint joinPoint) throws Throwable {
    System.out.println("Before");
    Object result = joinPoint.proceed();
    System.out.println("After");
    return result + " World";
}

medium

A. Before
Hello
After
World

B. Hello
Before
After
World

C. Before
After
Hello

D. Before
After
Hello World

Solution

1. Step 1: Trace the advice execution order

   The advice prints "Before", then calls the original method which returns "Hello", then prints "After".

2. Step 2: Understand the returned value

   The advice returns the original result plus " World", so the final returned string is "Hello World".

3. Final Answer:

   Before After Hello World -> Option D

4. Quick Check:

   Prints before and after, returns modified result [OK]

Hint: Remember @Around runs code before and after proceed() [OK]

Common Mistakes:

• Assuming original method output is unchanged
• Mixing print order with return value
• Forgetting to add " World" to result

4. Identify the error in this @Around advice method:

@Around("execution(* someMethod())")
public Object aroundAdvice(ProceedingJoinPoint joinPoint) {
    System.out.println("Start");
    Object result = joinPoint.proceed();
    System.out.println("End");
    return result;
}

medium

A. Incorrect annotation syntax

B. Missing throws Throwable declaration in method signature

C. Should call joinPoint.execute() instead of proceed()

D. Cannot return Object type from advice

Solution

1. Step 1: Check method signature requirements

   joinPoint.proceed() throws Throwable, so the advice method must declare throws Throwable or handle it.

2. Step 2: Identify missing throws declaration

   The method lacks "throws Throwable", causing a compile error.

3. Final Answer:

   Missing throws Throwable declaration in method signature -> Option B

4. Quick Check:

   proceed() throws Throwable, must declare it [OK]

Hint: Add throws Throwable when calling joinPoint.proceed() [OK]

Common Mistakes:

• Ignoring checked exceptions from proceed()
• Using wrong method name instead of proceed()
• Not matching annotation syntax

5. You want to create an @Around advice that modifies the input argument of a method before execution and changes the returned result after execution. Which approach correctly achieves this?

hard

A. Modify the method parameters directly without using proceed, then return null

B. Call joinPoint.proceed() without arguments, then ignore the result and return a new value

C. Modify the argument array via joinPoint.getArgs(), then call joinPoint.proceed(modifiedArgs), and finally modify the returned result before returning

D. Use joinPoint.proceed() and modify the result, but cannot change input arguments

Solution

1. Step 1: Understand argument modification in @Around advice

   You can get and modify method arguments using joinPoint.getArgs() and pass them to proceed() to change inputs.

2. Step 2: Modify the returned result after proceed()

   After calling proceed with modified arguments, you can change the returned value before returning it.

3. Final Answer:

   Modify the argument array via joinPoint.getArgs(), then call joinPoint.proceed(modifiedArgs), and finally modify the returned result before returning -> Option C

4. Quick Check:

   Change inputs with proceed(args), then modify output [OK]

Hint: Use proceed(modifiedArgs) to change inputs, then modify output [OK]

Common Mistakes:

• Calling proceed() without modified arguments when inputs need change
• Trying to change parameters directly without proceed()
• Ignoring returned result modification