Pointcut expressions in Spring Boot - Mini Project: Build & Apply

Using Pointcut Expressions in Spring Boot

📖 Scenario: You are building a Spring Boot application that needs to log method calls in a service class. You want to use Aspect-Oriented Programming (AOP) to intercept method executions using pointcut expressions.

🎯 Goal: Create a Spring Boot aspect that uses pointcut expressions to match all methods in the CalculatorService class and logs a message before each method runs.

📋 What You'll Learn

Create a CalculatorService class with two methods: add and subtract.

Create an aspect class called LoggingAspect.

Define a pointcut expression that matches all methods in CalculatorService.

Add a @Before advice that logs a message before any matched method executes.

💡 Why This Matters

🌍 Real World

Logging method calls is common in real applications to track behavior and debug issues without changing business logic.

💼 Career

Understanding pointcut expressions and AOP is important for backend developers working with Spring Boot to implement cross-cutting concerns like logging, security, and transactions.

1

Create CalculatorService with methods

Create a class called CalculatorService with two public methods: add that takes two integers and returns their sum, and subtract that takes two integers and returns their difference.

Spring Boot

public class CalculatorService {
    // Your code here
}

Need a hint?

Define a public class named CalculatorService. Add two public methods named add and subtract with two integer parameters each. Return the sum and difference respectively.

2

Create LoggingAspect class with @Aspect annotation

Create a class called LoggingAspect and annotate it with @Aspect and @Component to make it a Spring-managed aspect.

Spring Boot

public class CalculatorService {
    public int add(int a, int b) {
        return a + b;
    }

    public int subtract(int a, int b) {
        return a - b;
    }
}

// Your code here

Need a hint?

Import @Aspect and @Component. Annotate the class LoggingAspect with both annotations.

3

Define pointcut expression for CalculatorService methods

Inside LoggingAspect, define a pointcut method called allCalculatorMethods annotated with @Pointcut. Use the expression execution(* CalculatorService.*(..)) to match all methods in CalculatorService.

Spring Boot

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

@Aspect
@Component
public class LoggingAspect {
    // Your code here
}

Need a hint?

Use @Pointcut annotation with the expression execution(* CalculatorService.*(..)). Define an empty method named allCalculatorMethods to hold this pointcut.

4

Add @Before advice to log before method execution

Add a @Before advice method called logBeforeMethod in LoggingAspect that uses the pointcut allCalculatorMethods(). Inside the method, add a simple log statement using System.out.println that prints "Method is about to execute".

Spring Boot

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.annotation.Before;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class LoggingAspect {
    @Pointcut("execution(* CalculatorService.*(..))")
    public void allCalculatorMethods() {}

    // Your code here
}

Need a hint?

Use @Before annotation with the pointcut method allCalculatorMethods(). Define a method logBeforeMethod that prints the log message.