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Learn these first

At a glance

1. 1Java's built-in HttpClient builds a HttpRequest and calls send (blocking) or sendAsync (returns a CompletableFuture)Spring offers RestTemplate (blocking), RestClient (modern blocking) and WebClient (reactive).
2. 2A response has a status code and a bodyA 404 or 500 is not an exception with the plain Java client; you must check statusCode(). Spring clients throw on 4xx and 5xx by default.
3. 3Always set a connect timeout and a request or read timeoutWithout them a slow dependency can hold your threads forever.

• Reuse client instances (they hold connection pools)
• Connections are pooled and reused with keep-alive; HTTP/2 multiplexes several requests over one connection

HttpClient client = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(3)).build();HttpRequest request = HttpRequest.newBuilder(URI.create("https://api.example.com/items/7"))    .timeout(Duration.ofSeconds(5)).GET().build();HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());if (response.statusCode() != 200) {    throw new IllegalStateException("unexpected status " + response.statusCode());}

1. line 1 uses HttpClient, the core of HTTP clients
2. line 2 uses HttpRequest, the core of HTTP clients
3. line 4 uses HttpResponse, the core of HTTP clients

How Unravel recognises it

When you paste code, Unravel looks for these signs of http clients. Spotting them yourself is a good habit when you read unfamiliar code:

• Annotations: @FeignClient
• Types: HttpClient HttpRequest HttpResponse RestTemplate WebClient RestClient OkHttpClient HttpURLConnection FeignClient CloseableHttpClient

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