EnableBinding is deprecated in Spring Cloud Stream 3.x

Question

I am using Kafka for a microservices project. I want to invoke an event whenever I save a record to the database. I have been looking at tutorials about Spring Cloud Stream. All of them are using @EnableBinding, @Input, @Output annotations. When I try to use them, it says they are deprecated. I am using spring initialzr. The release notes say that I should use Supplier, Consumer, and Function instead of the old methods like Input, Output, and Process.

@Bean
public Supplier<String> toUpperCase() {
    return () -> {
        return "hello from supplier";
    };
}

When I use a Supplier like this, it generates the message every second as it is also highlighted in the tutorials. I don't want it to be published every second. I want it to be published when I want it to. It says I should invoke its get() method but I don't know how. Tutorials use deprecated functions to achieve such a functionality. How can I achieve such behavior without deprecated functions or how can I use the EnableBinder annotation without it is saying it is deprecated?

Answer 1

You can check my repo for a demo project at https://github.com/HabeebCycle/spring-cloud-stream-implemention

It shows how to implement cloud-stream using RabbitMQ and Kafka for both the supplier and the consumer and also end-to-end testing of both services.

for your case: In your supplier bean do something like this:

@Bean
public Supplier<DataEvent<String, User>> savedMessage() {
    return () -> {
        return null;
    };
}

Spring provides StreamBridge in the function package that can be used to send events. Let's assume you have a service layer that saves into the database. The first thing to do is to create an autowired StreamBridge that is injected by constructor binding and use it to send your message as follows. Notice that the name of the supplier should be the binding name of your output as explained in the documentation.

private final StreamBridge stream;
private final UserRepository repo;

// Store your topic/binding name as the supplier name as follows
private static final String SUPPLIER_BINDING_NAME = "savedMessage-out-0"

public UserService(UserRepository repo, StreamBridge stream) {
   this.repo = repo;
   this.stream = stream;
}

// Your save method
public void saveUser(User user) {
  // Do some checking...

  //save your record
  User user = repo.save(user);
  
  //check if user is saved or not null
  //create your message event (Assuming you have a DataEvent class)
  DataEvent<String, User> event = new DataEvent<>("User Saved", user);
  boolean sent = stream.send(SUPPLIER_BINDING_NAME, event));

  // Check the repo above for proper implementation.
}

For the consumer implementation, check my repo above.

There is also an implementation here although written in Kotlin https://piotrminkowski.com/2020/06/05/introduction-to-event-driven-microservices-with-spring-cloud-stream/

You can also check Spring recent project on GitHub here https://github.com/spring-cloud/spring-cloud-stream-samples/