httpClientNotes.md

HttpClient

In Java 11, a brand-new HttpClient API was introduced in the java.net.http package — a modern, efficient, and fully asynchronous HTTP client that replaces the older HttpURLConnection.

Here’s a quick overview 👇

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🧩 Import

import java.net.http.*;
import java.net.URI;

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✅ Simple GET Request Example

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class SimpleGetExample {
    public static void main(String[] args) throws Exception {
        // Create HttpClient (thread-safe, can be reused)
        HttpClient client = HttpClient.newHttpClient();

        // Create Request
        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create("https://jsonplaceholder.typicode.com/posts/1"))
                .GET()
                .build();

        // Send Request (synchronous)
        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

        // Print Response
        System.out.println("Status Code: " + response.statusCode());
        System.out.println("Body: " + response.body());
    }
}

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⚙️ POST Request Example (with JSON)

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.net.http.HttpRequest.BodyPublishers;

public class SimplePostExample {
    public static void main(String[] args) throws Exception {
        HttpClient client = HttpClient.newHttpClient();

        String jsonBody = """
            {
              "title": "foo",
              "body": "bar",
              "userId": 1
            }
        """;

        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create("https://jsonplaceholder.typicode.com/posts"))
                .header("Content-Type", "application/json")
                .POST(BodyPublishers.ofString(jsonBody))
                .build();

        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

        System.out.println("Status Code: " + response.statusCode());
        System.out.println("Body: " + response.body());
    }
}

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⚡ Asynchronous Request Example

import java.net.URI;
import java.net.http.*;
import java.util.concurrent.CompletableFuture;

public class AsyncGetExample {
    public static void main(String[] args) {
        HttpClient client = HttpClient.newHttpClient();

        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create("https://jsonplaceholder.typicode.com/posts/1"))
                .build();

        CompletableFuture<HttpResponse<String>> future =
                client.sendAsync(request, HttpResponse.BodyHandlers.ofString());

        // Non-blocking
        future.thenApply(HttpResponse::body)
              .thenAccept(System.out::println)
              .join();
    }
}

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🛠️ Common Notes

Feature	Description
Package	java.net.http
HTTP/2 Support	Yes
Asynchronous API	Built-in via CompletableFuture
Redirects	Controlled using HttpClient.Builder.followRedirects()
Timeouts	Configurable per request
Proxy / SSL	Supported via HttpClient.Builder

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Example with Timeout and Redirects

HttpClient client = HttpClient.newBuilder()
        .followRedirects(HttpClient.Redirect.NORMAL)
        .connectTimeout(Duration.ofSeconds(10))
        .build();

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Would you like me to show an example that sends headers and reads JSON responses (parsed into a POJO) using HttpClient + Jackson?