Java HttpClient 代理接入示例

import java.net.Authenticator;
import java.net.InetSocketAddress;
import java.net.PasswordAuthentication;
import java.net.ProxySelector;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.time.Duration;

public final class ProxyExample {
    /**
     * 使用 JDK HttpClient 通过账密代理请求公开出口检测地址。
     */
    public static void main(String[] args) throws Exception {
        String proxyHost = System.getenv("PROXY_HOST");
        int proxyPort = Integer.parseInt(System.getenv("PROXY_PORT"));
        String proxyUsername = System.getenv("PROXY_USERNAME");
        char[] proxyPassword = System.getenv("PROXY_PASSWORD").toCharArray();

        HttpClient client = HttpClient.newBuilder()
            .connectTimeout(Duration.ofSeconds(10))
            .proxy(ProxySelector.of(new InetSocketAddress(proxyHost, proxyPort)))
            .authenticator(new Authenticator() {
                /** 仅向代理服务器提供认证信息，避免响应目标站认证挑战。 */
                @Override
                protected PasswordAuthentication getPasswordAuthentication() {
                    if (getRequestorType() != RequestorType.PROXY) return null;
                    return new PasswordAuthentication(proxyUsername, proxyPassword);
                }
            })
            .build();

        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://<public-test-host>/ip"))
            .timeout(Duration.ofSeconds(30))
            .GET()
            .build();
        HttpResponse<String> response = client.send(
            request,
            HttpResponse.BodyHandlers.ofString()
        );

        if (response.statusCode() >= 400) {
            throw new IllegalStateException("HTTP " + response.statusCode());
        }
        System.out.println(response.body());
    }
}