AsyncConfigurationException: No AsyncConfigurer found

Q: Add @EnableAsync annotation

When to use: Use this if your @Async methods are running synchronously or throwing config errors.. Spring Boot does not enable asynchronous processing by default. You must explicitly turn it on with @EnableAsync.

Q: Implement AsyncConfigurer interface

When to use: Use this if you want to define a custom thread pool or exception handler.. Create a configuration class that implements AsyncConfigurer to gain fine-grained control over how @Async tasks are executed.

Q: Avoid self-invocation

When to use: Use this if @EnableAsync is present but the method still runs synchronously.. Spring's @Async uses a proxy. If you call an @Async method from another method in the SAME class, the proxy is bypassed, and it runs synchronously. Inject the bean into itself.

🔴 The Error You're Seeing

Confirm this matches your console output. If it does, you're in the right place.

ERROR LOG

org.springframework.scheduling.annotation.AsyncConfigurationException: No AsyncConfigurer found.
	at org.springframework.scheduling.annotation.AsyncAnnotationBeanPostProcessor.setBeanFactory(AsyncAnnotationBeanPostProcessor.java:123)

⚡ Quick Fix Works 80% of the time

Add @EnableAsync to your main Application class or a @Configuration class.

@SpringBootApplication
@EnableAsync
public class Application { ... }

🧠 Why this Happens

Tap to expand the deep technical explanation

You used the @Async annotation, but Spring's asynchronous execution infrastructure is either not enabled (missing @EnableAsync) or misconfigured. Without an AsyncConfigurer, Spring doesn't know which thread pool to use to execute the background task.

The HITEC City Parking Spot Analogy:

Imagine a restaurant manager asking a waiter to clean tables, but the manager never hired a cleaning staff (Thread Pool). The waiter has to clean the tables themselves, blocking the main dining room.

🔁 How to Reproduce Confirm this is your error

Annotate a method with @Async but forget to add @EnableAsync, then call it. Spring throws AsyncConfigurationException: No AsyncConfigurer found.

🛠️ Solutions (3 Ways to Fix)

Solution 1✓ Most common cause

Add @EnableAsync annotation

👉 Use this if your @Async methods are running synchronously or throwing config errors.

Spring Boot does not enable asynchronous processing by default. You must explicitly turn it on with @EnableAsync.

@SpringBootApplication
@EnableAsync // Add this
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

Solution 2

Implement AsyncConfigurer interface

👉 Use this if you want to define a custom thread pool or exception handler.

Create a configuration class that implements AsyncConfigurer to gain fine-grained control over how @Async tasks are executed.

@Configuration
@EnableAsync
public class AsyncConfig implements AsyncConfigurer {
    @Override
    public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(5);
        executor.setMaxPoolSize(10);
        executor.initialize();
        return executor;
    }
}

Solution 3

Avoid self-invocation

👉 Use this if @EnableAsync is present but the method still runs synchronously.

Spring's @Async uses a proxy. If you call an @Async method from another method in the SAME class, the proxy is bypassed, and it runs synchronously. Inject the bean into itself.

@Service
public class ReportService {
    @Autowired
    private ReportService self; // Inject self

    public void generate() {
        self.generateAsync(); // Calls through proxy
    }

    @Async
    public void generateAsync() { ... }
}

📋 Version Notes

Spring Boot 2.x

Uses SimpleAsyncTaskExecutor by default if no custom pool is defined.

Spring Boot 3.x

Requires explicit configuration for robust production use.

🛡️ How to Prevent This Next Time

Always create a custom ThreadPoolTaskExecutor bean when using @Async in production to prevent unbounded thread creation.