Java 發送 HTTP 請求兩大方案：HttpClient 4.x 與 HttpURLConnection 對比

方案一：Apache HttpClient 4.x（推薦企業級）

功能豐富：連線池、自動重試、攔截器、多執行緒安全、支援各種認證機制。

public static String sendUrlRequest(String urlStr, String param1, String param2) throws Exception {
    HttpClient httpClient = new DefaultHttpClient();
    // 連線池與超時配置
    httpClient.getParams().setIntParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 20000);
    httpClient.getParams().setIntParameter(CoreConnectionPNames.SO_TIMEOUT, 20000);

    List<NameValuePair> nvps = new ArrayList<>();
    nvps.add(new BasicNameValuePair("mainMemoCode", param1));
    nvps.add(new BasicNameValuePair("recordPassWord", param2));

    HttpPost httpPost = new HttpPost(urlStr);
    httpPost.setEntity(new UrlEncodedFormEntity(nvps, "GBK")); // 編碼視伺服器而定

    HttpResponse response = httpClient.execute(httpPost);
    String contentType = response.getHeaders("Content-Type")[0].getValue();
    HttpEntity entity = response.getEntity();
    String result = EntityUtils.toString(entity);

    httpPost.abort();
    httpClient.getConnectionManager().shutdown();
    return result;
}

優勢總結

• 連線管理：PoolingClientConnectionManager 可複用連線，高併發效能優異
• 攔截器鏈：可統一加簽、日志、重試邏輯
• 流式處理：HttpEntity 支援大檔案不佔記憶體

方案二：原生 HttpURLConnection（輕量場景）

public static String sendUrlRequest(String urlStr, String param) throws Exception {
    HttpURLConnection conn = null;
    try {
        URL url = new URL(urlStr);
        conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("POST");
        conn.setDoOutput(true);
        conn.setRequestProperty("User-Agent", "directclient");
        conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded; charset=GBK");

        try (PrintWriter out = new PrintWriter(new OutputStreamWriter(conn.getOutputStream(), "GBK"))) {
            out.println(param);
        }

        StringBuilder sb = new StringBuilder();
        try (BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "GBK"))) {
            String line;
            while ((line = in.readLine()) != null) sb.append(line);
        }
        return sb.toString();
    } finally {
        if (conn != null) conn.disconnect();
    }
}

適用場景

• 簡單單次請求、無高併發、不想引入第三方 JAR
• Android 早期版本（HttpClient 已移除）

深度對比表

選型建議

• 新專案 / 高併發 / 複雜業務：優先 Apache HttpClient 5.x 或 OkHttp
• 舊專案維護 / 受限環境 / 簡單需求：HttpURLConnection 即可
• Android：OkHttp 或 java.net.http.HttpClient (API 29+)

現代化替代：Java 11+ HttpClient

HttpClient client = HttpClient.newHttpClient();
HttpRequest request = HttpRequest.newBuilder()
    .uri(URI.create(urlStr))
    .header("Content-Type", "application/x-www-form-urlencoded")
    .POST(HttpRequest.BodyPublishers.ofString(params))
    .build();
String response = client.send(request, HttpResponse.BodyHandlers.ofString()).body();

標準化、支援 HTTP/2、非阻塞、函數式 API，長期來看為最佳選擇。