2. 使用HttpURLConnection发起POST请求提交表单数据

POST 表单提交的核心链路

GET 把参数拼在 URL 上，POST 则把键值对写进请求体。用 HttpURLConnection 发 POST 时，真正决定服务端能否正确解析表单的是三件事：请求方法设为 POST、Content-Type 声明为 application/x-www-form-urlencoded、以及通过输出流写入经过 URL 编码的键值对。三者缺一，服务端就可能收到空体或解析失败。

关键代码实现

下面是一个完整的 POST 表单提交方法。它把参数编码、请求头设置、输出流写入和响应读取串在一起，可直接放入 Android 项目的工具类中调用。

public static String postForm(String urlStr, Map<String, String> params) throws IOException {
    HttpURLConnection conn = null;
    try {
        URL url = new URL(urlStr);
        conn = (HttpURLConnection) url.openConnection();

        // 1. 请求方法与超时
        conn.setRequestMethod("POST");
        conn.setConnectTimeout(8000);
        conn.setReadTimeout(8000);

        // 2. 允许输出，并声明表单类型
        conn.setDoOutput(true);
        conn.setRequestProperty("Content-Type",
                "application/x-www-form-urlencoded;charset=UTF-8");

        // 3. 拼接并编码键值对
        StringBuilder body = new StringBuilder();
        for (Map.Entry<String, String> e : params.entrySet()) {
            if (body.length() > 0) body.append('&');
            body.append(URLEncoder.encode(e.getKey(), "UTF-8"))
                .append('=')
                .append(URLEncoder.encode(e.getValue(), "UTF-8"));
        }
        byte[] bytes = body.toString().getBytes(StandardCharsets.UTF_8);

        // 4. 写入请求体
        conn.setFixedLengthStreamingMode(bytes.length);
        try (OutputStream os = conn.getOutputStream()) {
            os.write(bytes);
            os.flush();
        }

        // 5. 读取响应
        int code = conn.getResponseCode();
        InputStream is = (code >= 200 && code < 300)
                ? conn.getInputStream() : conn.getErrorStream();

        StringBuilder resp = new StringBuilder();
        try (BufferedReader br = new BufferedReader(
                new InputStreamReader(is, StandardCharsets.UTF_8))) {
            String line;
            while ((line = br.readLine()) != null) {
                resp.append(line);
            }
        }
        return "code=" + code + ", body=" + resp;
    } finally {
        if (conn != null) conn.disconnect();
    }
}

调用与结果判读

在子线程中调用，并把返回结果回传到主线程更新 UI：

new Thread(() -> {
    try {
        Map<String, String> form = new HashMap<>();
        form.put("name", "张三");
        form.put("age", "28");
        String result = postForm("https://httpbin.org/post", form);
        runOnUiThread(() -> tvResult.setText(result));
    } catch (IOException e) {
        runOnUiThread(() -> tvResult.setText("请求失败：" + e.getMessage()));
    }
}).start();