Build Reactive MicroServices using Spring WebFlux/SpringBoot

It looks like you're outlining a comprehensive guide to building a reactive application with Spring WebFlux, MongoDB, and WebClient, focusing on non-blocking APIs and real-time data streaming. Here's a breakdown of the content you've described, along with some additional context where needed:

1. Introduction to Reactive Programming: This section would cover the basics of reactive programming, including its principles and how it differs from traditional imperative programming. It would also introduce the concept of backpressure and how it is handled in a reactive stream.

2. Spring WebFlux & Netty - Execution Model: Here you would explain how Spring WebFlux leverages Netty as its underlying reactor-netty support to handle non-blocking IO operations for handling HTTP requests and responses. This section would also cover the different layers of Spring WebFlux, including the web server factory (Netty, Tomcat, etc.), controller layer, and routing layer.

3. RouterFunction and HandlerFunction: These are key components in Spring WebFlux that allow you to define routes and their corresponding handlers in a functional style. You would learn how to use RouterFunction to route requests to specific HandlerFunctions.

4. WebTestClient for Testing: This section would teach you how to write non-blocking test cases for your reactive endpoints using WebTestClient, a non-blocking HTTP client for testing web applications in a Java environment.

5. Reactive API with RestController: Here you would build a reactive endpoint using @RestController annotated classes and methods, and learn how to integrate them with reactive data sources like MongoDB. You would also write tests using JUNIT and WebTestClient to validate the CRUD operations.

6. Reactive API with Functional Web: In this section, you would use the functional programming approach provided by Spring WebFlux to build your reactive endpoints. This includes defining routes and handlers using Function and Mono or Flux types directly. You would again write tests for these endpoints.

7. Build Non Blocking Client using WebClient: This section would cover how to use the WebClient utility provided by Spring WebFlux to make non-blocking calls to other reactive services or APIs. You would learn about the different methods available in WebClient, such as exchange(), retrieve(), and how to handle the various HTTP methods (GET, PUT, POST, DELETE) with it.

8. Handling Exceptions: In this section, you would explore different ways to handle exceptions within your reactive application. For RestController based endpoints, you would use @ExceptionHandler and @ControllerAdvice. For functional endpoints, you would learn about the WebExceptionHandler. You would also write tests for these exception handling scenarios using JUNIT.

9. Streaming Real Time Data using WebFlux - Server Side Events (SSE): In this final section, you would build an endpoint that streams real-time data from MongoDB to the client using Server Side Events (SSE). You would cover the use of tailable cursors and capped collections in MongoDB, and how to leverage the @Tailable annotation in Spring WebFlux to achieve this. You would also write JUNIT tests for your streaming endpoints.

This outline provides a comprehensive roadmap for building a full-stack reactive application with Spring WebFlux and MongoDB, covering both backend and frontend aspects of a reactive system. It emphasizes the importance of writing clean, well-tested code and understanding how to effectively handle real-time data streaming and exception scenarios within a reactive context.