How to retrieve List by a Consumer with Spring and rabbitmq

Question

I have two projects

1. WebApp(SpringMVC)
2. Microservice

The idea is that I have a page in which I list all the users from DB, so basically I need a listener on WebApp side and a producer in the microservice side, typically the flow is as follow

Whitout rabbitmq(synchronous)

1. Click page "List Users"

2. UserController that redirect me to a specific service

   public List<User>getUsers(){//no args!!
      service.getUsers();//no args
   }
   

3. UserService with logic to access DB and retrieve all users

   public List<User>getUsers(){//no args!!
      //connect to DB and retrieve all users
      return users
   }
   

4. Render users on jsp

With RabbitMQ and assuming users has already been produced the list of users on the microservice's side

My question is about if I introduce rabbitmq then I need a method in which I listen a message(List of products as a JSON) but now the flow change a little bit comparing with the first one because

1. Click button "List Users"

2. Controller need a method findAll(Message message), here I need pass a message because the service is expecting one as the service is Listener

   public List<User>getUsers(Message message){
       service.getAllUsers(**String message**);
   }
   

3. The service as right now is listen a message, I need to pass a Message arg in which I will be listen the queues

   @RabbitListener(queues = "${queue}", containerFactory = "fac")
   public List<User> getUsers(String message){
        //Transform JSON to POJO 
        //some logic...
        return users;
   
   }
   

   So basically my question is the second flow is correct?

   If so how I have to pass the Message object from controller to service because in controller I do not needed a Message, but in order to listen I have, is this correct?

   If so how pass the message arg

   There is a better way to achieve this?

   Regards

Answer 1

Use a Jackson2JsonMessageConverter and the framework will do all the conversion for you.

Controller:

List<User> users = template.convertSendAndReceiveAsType("someExchange", "someRoutingKey", 
    myRequestPojo, new ParameterizedTypeReference<List<User>>() {});

Server:

@RabbitListener(queues = "${queue}", containerFactory = "fac")
public List<User> getUsers(SomeRequestPojo request){
     //some logic...
     return users;
}

Wire the converter into both the listener container factory and the RabbitTemplate.

Request Pojo and Users have to be Jackson-friendly (no-arg constructor, setters).