Spring AOP

Full Reference: See patterns.md for Performance Monitoring, Retry Logic, Audit Logging, Security Check, Rate Limiting, and Testing patterns.

Quick Start

@SpringBootApplication @EnableAspectJAutoProxy public class Application {}

@Aspect @Component @Slf4j public class LoggingAspect {

@Around("execution(* com.example.service.*.*(..))")
public Object logExecution(ProceedingJoinPoint joinPoint) throws Throwable {
    String method = joinPoint.getSignature().toShortString();
    log.info("Executing: {}", method);

    long start = System.currentTimeMillis();
    Object result = joinPoint.proceed();
    long duration = System.currentTimeMillis() - start;

    log.info("Completed: {} in {} ms", method, duration);
    return result;
}

}

Pointcut Expressions

Method Execution

@Aspect @Component public class PointcutExamples {

// All methods in a package
@Pointcut("execution(* com.example.service.*.*(..))")
public void serviceLayer() {}

// Public methods
@Pointcut("execution(public * *(..))")
public void publicMethods() {}

// Methods starting with "get"
@Pointcut("execution(* get*(..))")
public void getters() {}

// Package and subpackages
@Pointcut("execution(* com.example..*.*(..))")
public void entireApplication() {}

}

Annotation-Based

@Aspect @Component public class AnnotationPointcuts {

// Methods annotated with @Transactional
@Pointcut("@annotation(org.springframework.transaction.annotation.Transactional)")
public void transactionalMethods() {}

// Classes annotated with @Service
@Pointcut("@within(org.springframework.stereotype.Service)")
public void serviceBeans() {}

// With annotation binding
@Around("@annotation(loggable)")
public Object logWithAnnotation(ProceedingJoinPoint pjp, Loggable loggable) throws Throwable {
    String value = loggable.value();
    return pjp.proceed();
}

}

Combinations

@Aspect @Component public class CombinedPointcuts {

@Pointcut("execution(* com.example.service.*.*(..))")
public void serviceLayer() {}

@Pointcut("execution(* com.example.repository.*.*(..))")
public void repositoryLayer() {}

// AND
@Pointcut("serviceLayer() && publicMethods()")
public void publicServiceMethods() {}

// OR
@Pointcut("serviceLayer() || repositoryLayer()")
public void dataLayer() {}

// NOT
@Pointcut("serviceLayer() && !execution(* get*(..))")
public void nonGetterServiceMethods() {}

}

Advice Types

@Around

@Aspect @Component public class AroundAdvice {

@Around("execution(* com.example.service.*.*(..))")
public Object aroundAdvice(ProceedingJoinPoint joinPoint) throws Throwable {
    String methodName = joinPoint.getSignature().getName();
    Object[] args = joinPoint.getArgs();

    log.info("Before: {} with args: {}", methodName, Arrays.toString(args));

    try {
        Object result = joinPoint.proceed();
        log.info("After returning: {} returned: {}", methodName, result);
        return result;
    } catch (Exception e) {
        log.error("After throwing: {} threw: {}", methodName, e.getMessage());
        throw e;
    }
}

// Modify arguments
@Around("execution(* com.example.service.UserService.createUser(..))")
public Object sanitizeInput(ProceedingJoinPoint joinPoint) throws Throwable {
    Object[] args = joinPoint.getArgs();
    for (int i = 0; i < args.length; i++) {
        if (args[i] instanceof String str) {
            args[i] = sanitize(str);
        }
    }
    return joinPoint.proceed(args);
}

}

@Before, @After, @AfterReturning, @AfterThrowing

@Aspect @Component public class OtherAdvice {

@Before("execution(* com.example.service.*.*(..))")
public void logBefore(JoinPoint joinPoint) {
    log.info("Entering: {}", joinPoint.getSignature().toShortString());
}

@After("execution(* com.example.service.*.*(..))")
public void logAfter(JoinPoint joinPoint) {
    log.info("Completed: {}", joinPoint.getSignature().toShortString());
}

@AfterReturning(pointcut = "execution(* com.example.service.UserService.createUser(..))", returning = "user")
public void logCreatedUser(JoinPoint joinPoint, User user) {
    log.info("Created user: {}", user.getId());
}

@AfterThrowing(pointcut = "execution(* com.example.service.*.*(..))", throwing = "ex")
public void logException(JoinPoint joinPoint, Exception ex) {
    log.error("Exception in {}: {}", joinPoint.getSignature().toShortString(), ex.getMessage());
}

}

Custom Annotations

@Target({ElementType.METHOD, ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) public @interface Loggable { String value() default ""; boolean logArgs() default true; boolean logResult() default true; LogLevel level() default LogLevel.INFO; }

@Aspect @Component @Slf4j public class LoggableAspect {

@Around("@annotation(loggable)")
public Object logMethod(ProceedingJoinPoint joinPoint, Loggable loggable) throws Throwable {
    String methodName = joinPoint.getSignature().toShortString();
    String message = loggable.value().isEmpty() ? methodName : loggable.value();

    if (loggable.logArgs()) {
        log.info("Entering {} with args: {}", message, Arrays.toString(joinPoint.getArgs()));
    }

    long start = System.currentTimeMillis();
    Object result = joinPoint.proceed();

    if (loggable.logResult()) {
        log.info("Exiting {} with result: {} ({}ms)", message, result, System.currentTimeMillis() - start);
    }
    return result;
}

}

// Usage @Service public class UserService { @Loggable(value = "Creating user", logResult = false) public User createUser(CreateUserRequest request) { return userRepository.save(new User(request)); } }

Aspect Ordering

@Aspect @Component @Order(1) // Executes first public class SecurityAspect { }

@Aspect @Component @Order(2) // Executes second public class LoggingAspect { }

@Aspect @Component @Order(3) // Executes third public class PerformanceAspect { }

Best Practices

• Use specific pointcuts (not too broad)

• Order aspects with @Order

• Use custom annotations for clarity

• Avoid complex logic in aspects

• Monitor performance impact

• Test aspects in isolation

• Don't catch exceptions silently

• Don't modify shared state

• Don't use for core business logic

Common Pitfalls

Error Cause Solution

Aspect not applied Bean not Spring-managed Use @Component or @Bean

Self-invocation Internal call bypasses proxy Use self-injection

Wrong order Aspects not ordered Use @Order

Performance Aspect too broad Narrow pointcut

Quick Troubleshooting

Issue Possible Cause Solution

Aspect not executing Bean not Spring-managed Ensure class has @Component

Self-invocation doesn't trigger Internal call bypasses proxy Use self-injection

Wrong execution order Missing @Order Add @Order with priority

Performance degradation Pointcut too broad Narrow scope, use custom annotations

Reference Documentation

• Spring AOP

• AspectJ Pointcut Expressions