java.net.http.HttpClient

ไคลเอ็นต์ HTTP สมัยใหม่

การสร้าง HttpClient

import java.net.http.HttpClient;
import java.time.Duration;

public class Main {
    public static void main(String[] args) {
        HttpClient client = HttpClient.newBuilder()
            .version(HttpClient.Version.HTTP_2)
            .connectTimeout(Duration.ofSeconds(10))
            .build();
        System.out.println("Client version: " + client.version());
    }
}

การสร้างคำขอ

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

public class Main {
    public static void main(String[] args) {
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://example.com/data"))
            .GET()
            .build();
        System.out.println("Method: " + request.method());
        System.out.println("URI: " + request.uri());
    }
}

การส่งแบบซิงโครนัส

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

public class Main {
    public static void main(String[] args) throws Exception {
        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://example.com"))
            .build();
        HttpResponse<String> response =
            client.send(request, HttpResponse.BodyHandlers.ofString());
        System.out.println("Status: " + response.statusCode());
    }
}

การอ่านรหัสสถานะ

public class Main {
    public static void main(String[] args) {
        int status = 404;
        String label;
        if (status >= 200 && status < 300) label = "Success";
        else if (status >= 300 && status < 400) label = "Redirect";
        else if (status >= 400 && status < 500) label = "Client error";
        else label = "Server error";
        System.out.println(status + " -> " + label);
    }
}

การอ่านเนื้อหา

public class Main {
    public static void main(String[] args) {
        String body = "{\"message\":\"hello\"}";
        System.out.println("Body length: " + body.length());
        System.out.println("Body: " + body);
    }
}

การจัดการการเปลี่ยนเส้นทาง

import java.net.http.HttpClient;

public class Main {
    public static void main(String[] args) {
        HttpClient client = HttpClient.newBuilder()
            .followRedirects(HttpClient.Redirect.NORMAL)
            .build();
        System.out.println("Redirect policy: " + client.followRedirects());
    }
}

ระยะหมดเวลาต่อคำขอ

import java.net.URI;
import java.net.http.HttpRequest;
import java.time.Duration;

public class Main {
    public static void main(String[] args) {
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://example.com"))
            .timeout(Duration.ofSeconds(5))
            .build();
        System.out.println("Timeout set: " + request.timeout().isPresent());
    }
}

การตรวจสอบส่วนหัวการตอบกลับ

import java.util.Optional;

public class Main {
    public static void main(String[] args) {
        // Simulating a header lookup result
        Optional<String> contentType = Optional.of("application/json");
        System.out.println("Content-Type: " + contentType.orElse("unknown"));
    }
}

ข้อยกเว้นที่ต้องจัดการ

import java.io.IOException;

public class Main {
    public static void main(String[] args) {
        try {
            // client.send(...) would go here
            throw new IOException("connection refused");
        } catch (IOException e) {
            System.out.println("Network problem: " + e.getMessage());
        }
    }
}

ไคลเอนต์ที่นำกลับมาใช้ซ้ำได้

import java.net.http.HttpClient;

public class Main {
    private static final HttpClient SHARED = HttpClient.newHttpClient();

    public static void main(String[] args) {
        System.out.println("Shared client ready: " + (SHARED != null));
    }
}

ตรวจสอบความเข้าใจ

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