Spring Cloud Stream - Event Routing

@SpringBootApplication
public class GFGApplication {

    public static void main(String[] args) {
        // Start the Spring Boot application with Cloud Stream function routing enabled
        SpringApplication.run(GFGApplication.class, "--spring.cloud.stream.function.routing.enabled=true");
    }

    // Bean definition for handling even numbers
    @Bean
    public Consumer<String> evenConsumer() {
        return value -> {
            // Print a message indicating that the value is even
            System.out.println("EVEN: " + value);
        };
    }

    // Bean definition for handling odd numbers
    @Bean
    public Consumer<String> oddConsumer() {
        return value -> {
            // Print a message indicating that the value is odd
            System.out.println("ODD: " + value);
        };
    }
}

@SpringBootApplication
public class RoutingStreamApplication {

    public static void main(String[] args) {
        // Start the Spring Boot application with a routing expression for determining even or odd
        SpringApplication.run(RoutingStreamApplication.class,
                "--spring.cloud.function.routing-expression="
                        + "T(java.lang.System).nanoTime() % 2 == 0 ? 'even' : 'odd'");
    }

    // Bean definition for handling even numbers
    @Bean
    public Consumer<Integer> evenConsumer() {
        return value -> {
            // Print a message indicating that the value is even
            System.out.println("EVEN: " + value);
        };
    }

    // Bean definition for handling odd numbers
    @Bean
    public Consumer<Integer> oddConsumer() {
        return value -> {
            // Print a message indicating that the value is odd
            System.out.println("ODD: " + value);
        };
    }
}

@SpringBootApplication
@Controller
public class SourceDestination {

    // Define a function that sets the payload and destination header
    @Bean
    public Function<String, Message<String>> destinationAsPayload() {
        return value -> {
            // Build a message with the payload and set the destination header
            return MessageBuilder.withPayload(value)
                    .setHeader("spring.cloud.stream.sendto.destination", value)
                    .build();
        };
    }
}

@Controller
public class SourceDestination {

    private static final String ID_KEY = "id";

    @Autowired
    private ObjectMapper jsonMapper;

    // Create an EmitterProcessor and a FluxSink to emit messages
    private final EmitterProcessor<Map<String, String>> processor = EmitterProcessor.create();
    private final FluxSink<Map<String, String>> fluxSink = processor.sink();

    // Handle HTTP POST requests with dynamic destination based on payload
    @PostMapping(path = "/", consumes = "*/*")
    @ResponseStatus(HttpStatus.ACCEPTED)
    public void handleRequest(@RequestBody String body,
                              @RequestHeader(HttpHeaders.CONTENT_TYPE) Object contentType) {
        try {
            // JSON body into Map
            Map<String, String> payload = jsonMapper.readValue(body, new TypeReference<Map<String, String>>() {});
            String destination = payload.get(ID_KEY);

            if (destination != null) {
                // Create a message with payload and set the destination header
                Message<Map<String, String>> message = MessageBuilder
                        .withPayload(payload)
                        .setHeader("spring.cloud.stream.sendto.destination", destination)
                        .build();
                // Emit the payload to the defined destination
                fluxSink.next(message.getPayload());
            } else {
                // Handle case where destination is not specified
                // You might want to log or perform some other action here
            }
        } catch (Exception e) {
            // Handle exceptions that might occur during JSON parsing or message processing
            // You might want to log or perform some other action here
        }
    }

    // Define a Supplier bean to act as the source of the Flux
    @Bean
    public Supplier<Flux<Map<String, String>>> source() {
        return () -> processor;
    }
}