Pointcut expressions in Spring Boot

Introduction

Pointcut expressions help you pick specific places in your code to add extra behavior without changing the original code.

You want to log every time a method in a service class runs.

You need to check user permissions before certain methods execute.

You want to measure how long some methods take to run.

You want to handle errors in a consistent way across many methods.

Syntax

Spring Boot

execution(modifiers-pattern? ret-type-pattern declaring-type-pattern? method-name-pattern(param-pattern) throws-pattern?)

The execution keyword is the most common way to write pointcut expressions.

Use * as a wildcard to match any part, like any method name or any return type.

Examples

Matches any method in any class inside the com.example.service package.

Spring Boot

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

Matches any public method regardless of class or package.

Spring Boot

execution(public * *(..))

Matches any method starting with find in UserRepository class.

Spring Boot

execution(* com.example.repository.UserRepository.find*(..))

Matches methods starting with delete that take a single Long parameter and return void in controller package.

Spring Boot

execution(void com.example.controller.*.delete*(Long))

Sample Program

This example shows a logging aspect that runs before any method in the com.example.service package. When createUser runs, the aspect prints a message first.

Spring Boot

package com.example.aop;

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

@Aspect
@Component
public class LoggingAspect {

    @Before("execution(* com.example.service.*.*(..))")
    public void logBefore() {
        System.out.println("A method in service package is about to run.");
    }
}

// Sample service class
package com.example.service;

import org.springframework.stereotype.Service;

@Service
public class UserService {
    public void createUser() {
        System.out.println("User created.");
    }
}

// Main application to run
package com.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import com.example.service.UserService;

@SpringBootApplication
public class DemoApplication {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(DemoApplication.class, args);
        UserService userService = context.getBean(UserService.class);
        userService.createUser();
    }
}

Important Notes

Pointcut expressions are very flexible and can match many method patterns.

Be careful with wildcards to avoid matching too many methods unintentionally.

Use Spring Boot DevTools or your IDE debugger to test if your pointcuts are working as expected.

Summary

Pointcut expressions select where extra code runs without changing original methods.

Use execution() with wildcards to match methods by name, package, or parameters.

They help add logging, security, or other features cleanly and easily.