Workshop Reactive Programming

This workshop is part of my presentation: Thinking Reactive.

In this workshop you'll learn the basics and some more advanced topics regarding Reactive Programming in Java. All samples will use RxJava2, but feel free to use Project Reactor instead.

1. Creating Publishers

This section is about creating Publishers.

Fix the TODOs in the reactive-samples module (by replacing the empty Publishers) in all CreateSample* classes in the package com.rudolfs.reactive.workshop.create.

2. Using operators

In this section you'll work with various Reactive Programming operators, like map, flatMap, filter, merge, delay, concatMap, takeUntil, zip, etc.

Fix the TODOs in the reactive-samples module in all OperatorSample* classes in the package com.rudolfs.reactive.workshop.operators.

3. Flow Control

This section is about flow control, which becomes important when consumers can't keep up with events emitted from within the producer.

The samples will show multiple ways to deal with flow control.

Fix the TODOs in the reactive-samples module in all FlowControlSample* classes in the package com.rudolfs.reactive.workshop.flowcontrol.

4. Integration with front-end

4.1 Server-Sent Events (SSE)

We're going to use Micronaut to implement the server side of SSE.

Open the TickController class in the micronaut-reactive module and have a look at the reactive return types of both methods.

Start the Application main class inside the micronaut-reactive module.

Use curl as the client:

curl -X GET -H "Accept:text/event-stream" http://localhost:8080/tick/10

The data events should be printed to your console now.

As an exercise, try to add some additional endpoints and/or logic within the existing endpoint.

4.2 WebSockets

We'll use Vert.x with RxJava2 to implement a WebSocket Server.

Open the RxWebSocketServer class in the vertx-reactive module and run the program, this will start a WebSocket Server listening on port 8080. Use e.g. Advanced Rest Client to send some messages
to the WebSocket Server by connecting to ws://localhost:8080. The WebSocket Server simulates the processing of a user's search action (from e.g. a web page) and streams the search results back to the WebSocket Client connection. The search operation is delayed on purpose to simulate a long running search.

Try to solve the TODO in the RxWebSocketServer.

Optional exercise: rewrite the WebSocketClient into a RxWebSocketClient (by using the io.vertx.reactivex.core.http.HttpClient).