The reactor.netty.http.client.PrematureCloseException: Connection prematurely closed BEFORE response error usually occurs when the server closes the connection before sending a complete response. Additionally, receiving 403 Forbidden or 401 Unauthorized suggests authentication or permission-related issues when interacting with the Stack Overflow API.

Possible Causes and Fixes:

1. Check Your Authentication Header

Ensure you're correctly passing the authentication token. If you're using an API key, it should be included as a query parameter or header. Example:

java

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WebClient webClient = WebClient.builder() .baseUrl("https://api.stackexchange.com/2.3") .defaultHeader(HttpHeaders.USER_AGENT, "YourAppName") .build(); Mono<String> response = webClient.get() .uri(uriBuilder -> uriBuilder .path("/questions") .queryParam("order", "desc") .queryParam("sort", "activity") .queryParam("site", "stackoverflow") .queryParam("key", "YOUR_API_KEY") // Ensure this is correct .build()) .retrieve() .bodyToMono(String.class); response.subscribe(System.out::println);