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Explanation

Async Programming in Spring Boot allows tasks to run in a separate thread without blocking the main thread. It is commonly used for email sending, report generation, file processing, and external API calls.

Code:

@EnableAsync
@SpringBootApplication
public class Application {
}

Explanation

Use the @Async annotation on a method to execute it asynchronously.

Code:

@Service
public class EmailService {

    @Async
    public void sendEmail() {
        System.out.println("
Sending email...");
    }
}

Explanation

The calling method continues execution without waiting for the async task to finish.

Code:

@Service
public class OrderService {

    @Autowired
    private EmailService emailService;

    public void processOrder() {
        emailService.sendEmail();
        System.out.println("Order 
processed");
    }
}

Explanation

An async method can return a value using CompletableFuture.

Code:

@Async
public CompletableFuture<String> 
generateReport() {
    return CompletableFuture.
completedFuture("Report Ready");
}

Explanation

Retrieve the result from the CompletableFuture when needed.

Code:

CompletableFuture<String> future =
 reportService.generateReport();
String result = future.get();

Explanation

Execution Flow: The main thread returns immediately while the async task runs in a background thread.

Code:

Request --> Main Thread --> Response 
Returned
                  
Main Thread--> Async Thread --> 
Long Running Task