The Spring team has kept the same annotations for both Spring MVC and Spring WebFlux as these annotations are non-blocking. Therefore, you can use the same annotations we have used in previous chapters for creating REST controllers. There, the annotation runs on Reactive Core and provides a non-blocking flow. However, you, as the developer, have the responsibility of maintaining a fully non-blocking flow and maintaining the Reactive chain (pipeline). Any blocking calls in a Reactive chain would convert the Reactive chain into a blocking call.

Let's create a simple REST controller that supports non-blocking and Reactive calls:

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@RestController

public class OrderController {

  @RequestMapping(value = "/api/v1/orders",

                     method = RequestMethod.POST)

  public ResponseEntity<Order> addOrder(@RequestBody NewOrder      

                                            newOrder){

     // …

  }

  @RequestMapping(value = "/api/v1/orders/{id}",

                     method = RequestMethod.GET)

  public ResponseEntity<Order> getOrderById(@PathVariable("id") 

                                            String id){

    // …

  }

}