Spring Boot – AOP Before Advice

Introduction

Spring Boot AOP (Aspect Oriented Programming) provides an interceptor-based mechanism, allowing us to define custom logic to be executed at various points throughout the application.

The @Before advice is one such type of advice that gets executed before the target method is called.

Implementation

To implement @Before advice in Spring Boot, we need to follow these steps:

1. Create an aspect class and annotate it with @Aspect.
2. Create a method and annotate it with @Before.
3. Define the pointcut expression that matches the target method and use it in the @Before annotation.

Here is an example:

@Aspect
@Component
public class MyAspect {

    @Before("execution(* com.example.demo.MyService.*(..))")
    public void beforeAdvice() {
        System.out.println("Executing `@Before` advice");
    }
}

In this example, we have created an aspect class called MyAspect and annotated it with @Aspect. We then have defined a method called beforeAdvice and annotated it with @Before. Finally, we have defined the pointcut expression execution(* com.example.demo.MyService.*(..)) that matches all methods of the MyService class.

Testing

To test our @Before advice, we can create a simple Spring Boot application and inject the MyService class into a controller:

@RestController
public class MyController {

    @Autowired
    private MyService myService;

    @GetMapping("/")
    public String hello() {
        myService.sayHello();
        return "Hello World";
    }
}

When we invoke the / endpoint of our application, the MyController will call the MyService.sayHello() method. Since we have defined a @Before advice on the MyService class, the beforeAdvice() method will get executed before the sayHello() method.

Conclusion

In this article, we have seen how to implement @Before advice in Spring Boot AOP. Using this advice, we can define custom logic that will get executed before the target method is called. This can be useful for adding security, logging, or performance monitoring to our application.