API Flavours

HiveMQ MQTT Client offers 3 different flavours of API:

• Blocking
• Asynchronous
• Reactive

Each of them has its own interface, so they are clearly separated and their methods can not be confused. Nevertheless it is possible to switch the API flavour at any time and use different API flavours of the same client concurrently.

For switching the API flavour simply call one of the to... methods as listed in the table below. Alternatively you can directly specify the API flavour when building the client by calling a specific build... method.

• Blocking
• Asynchronous
• Reactive

• The methods of the blocking API flavour directly return the results and block the current thread until those are available.

  • MQTT 5.0
  • MQTT 3.1.1

  • The interface of the blocking API flavour of a MQTT 5 Client is Mqtt5BlockingClient.

    Switching to the blocking API flavour:

    Mqtt5Client client = ...; // could be Mqtt5BlockingClient, Mqtt5AsyncClient or Mqtt5RxClient
    Mqtt5BlockingClient blockingClient = client.toBlocking();
    

    Building it directly:

    Mqtt5BlockingClient blockingClient = Mqtt5Client.builder().buildBlocking();
    

  • The interface of the blocking API flavour of a MQTT 3 Client is Mqtt3BlockingClient.

    Switching to the blocking API flavour:

    Mqtt3Client client = ...; // could be Mqtt3BlockingClient, Mqtt3AsyncClient or Mqtt3RxClient
    Mqtt3BlockingClient blockingClient = client.toBlocking();
    

    Building it directly:

    Mqtt3BlockingClient blockingClient = Mqtt3Client.builder().buildBlocking();
    

• The methods of the asynchronous API flavour have in common that they return CompletableFuture instead of waiting for the result. Additionally callbacks are used for the streams of incoming Publish messages.

  • MQTT 5.0
  • MQTT 3.1.1

  • The interface of the asynchronous API flavour of a MQTT 5 Client is Mqtt5AsyncClient.

    Switching to the asynchronous API flavour:

    Mqtt5Client client = ...; // could be Mqtt5BlockingClient, Mqtt5AsyncClient or Mqtt5RxClient
    Mqtt5AsyncClient asyncClient = client.toAsync();
    

    Building it directly:

    Mqtt5AsyncClient asyncClient = Mqtt5Client.builder().buildAsync();
    

  • The interface of the asynchronous API flavour of a MQTT 3 Client is Mqtt3AsyncClient.

    Switching to the asynchronous API flavour:

    Mqtt3Client client = ...; // could be Mqtt3BlockingClient, Mqtt3AsyncClient or Mqtt3RxClient
    Mqtt3AsyncClient asyncClient = client.toAsync();
    

    Building it directly:

    Mqtt3AsyncClient asyncClient = Mqtt3Client.builder().buildAsync();
    

• The reactive API flavour uses RxJava which is an implementation of Reactive Streams and the Reactive Extensions.

  As RxJava is compliant to the Reactive Streams specification it is easily interoperable with other reactive libraries such as Reactor Core.

  The reactive API flavour uses the RxJava data types Flowable, Single and Completable to expressively declare return types.

  • MQTT 5.0
  • MQTT 3.1.1

  • The interface of the reactive API flavour of a MQTT 5 Client is Mqtt5RxClient.

    Switching to the reactive API flavour:

    Mqtt5Client client = ...; // could be Mqtt5BlockingClient, Mqtt5AsyncClient or Mqtt5RxClient
    Mqtt5RxClient rxClient = client.toRx();
    

    Building it directly:

    Mqtt5RxClient rxClient = Mqtt5Client.builder().buildRx();
    

  • The interface of the reactive API flavour of a MQTT 3 Client is Mqtt3RxClient.

    Switching to the reactive API flavour:

    Mqtt3Client client = ...; // could be Mqtt3BlockingClient, Mqtt3AsyncClient or Mqtt3RxClient
    Mqtt3RxClient rxClient = client.toRx();
    

    Building it directly:

    Mqtt3RxClient rxClient = Mqtt3Client.builder().buildRx();