products-service

Great observation — the usage of WebClient, Flux, and Mono in Spring WebFlux follows a combination of modern design patterns and reactive programming paradigms. Let’s break it down:

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Design Patterns Behind WebClient, Flux, and Mono

1. Builder Pattern – WebClient

Instead of passing all values to a constructor or method, you build the request step by step:

WebClient.create()
         .get()
         .uri("/example")
         .header("Authorization", "Bearer token")
         .retrieve()
         .bodyToMono(String.class);

This is Builder Pattern:

• It allows constructing complex objects step-by-step.
• Each method returns the current builder instance.
• Makes the code more readable and chainable.

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2. Chain of Responsibility / Fluent Interface

• The chaining (.get().uri().retrieve()) is an example of Fluent Interface.
• It makes the code expressive and readable, encouraging immutability.

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3. Reactor Pattern – Flux and Mono

• Spring WebFlux is built on Project Reactor which implements the Reactive Streams specification.
• The core of Mono and Flux is asynchronous, non-blocking event handling, which is the essence of the Reactor Pattern.

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4. Publisher-Subscriber Pattern – Flux & Mono

Mono<String> result = webClient.get().uri("/data").retrieve().bodyToMono(String.class);
result.subscribe(System.out::println);

This is a Publisher-Subscriber or Observer pattern:

• Mono/Flux are Publishers.
• You can subscribe() to them to receive data when it’s ready.

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Why Not One Method With All Params?

Using method chaining instead of one giant method:

• Makes the code declarative and composable.
• Supports optional and dynamic configuration easily.
• Reduces parameter complexity and enhances clarity.

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Summary Table

Component	Pattern(s) Used	Purpose
WebClient	Builder, Fluent Interface	Build HTTP requests fluently
Mono/Flux	Reactor, Publisher-Subscriber	Non-blocking async programming
WebClient call chain	Chain of Responsibility, Builder	Step-by-step configuration

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Let me know if you’d like a visual UML or example transforming this into a custom builder class.