Spring Cloud Stream and @Publisher annotation compatiblity

Question

Since Spring Cloud Stream has not an annotation for sending a new message to a stream (@SendTo only works when @StreamListener is declared), I tried to use Spring Integratio

Answer 1

Why not just send the message to a stream manually, like below.

@Component
@Configuration
@EnableBinding(Processor.class)
public class Sender {

    @Autowired
    private Processor processor;

    public void send(String message) {

        processor.output().send(MessageBuilder.withPayload(message).build());

    }

}

You can test it through the tester.

@SpringBootTest
public class SenderTest {

    @Autowired
    private MessageCollector messageCollector;

    @Autowired
    private Processor processor;

    @Autowired
    private Sender sender;

    @SuppressWarnings("unchecked")
    @Test
    public void testSend() throws Exception{

        sender.send("Hi!");
        Message<String> message = (Message<String>) this.messageCollector.forChannel(this.processor.output()).poll(1, TimeUnit.SECONDS);
        String messageData = message.getPayload().toString();
        System.out.println(messageData);

    }

}

You should see "Hi!" in the console.

Answer 2

Since you use a @Publisher annotation in your ExampleService, it is proxied for that publishing stuff.

Only the way to overcome the issue is to expose an interface for your ExampleService and inject already that one into your test class:

public interface ExampleServiceInterface {

     String sendMessage(String message);

}

...

public class ExampleService implements ExampleServiceInterface {

...


@Autowired
private ExampleServiceInterface exampleService;

On the other hand it looks like your ExampleService.sendMessage() does nothing with the message, so you may consider to use a @MessagingGateway on some interface instead: https://docs.spring.io/spring-integration/reference/html/messaging-endpoints-chapter.html#gateway