java post请求方法

Java中发送POST请求的方法有很多种，以下是其中两种比较常用的方法：

1. 使用HttpURLConnection发送POST请求

public static String sendPost(String url, String param) {
    OutputStreamWriter out = null;
    BufferedReader in = null;
    StringBuilder result = new StringBuilder();
    try {
        URL realUrl = new URL(url);
        HttpURLConnection conn = (HttpURLConnection) realUrl.openConnection();
        // 设置通用的请求属性
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
        conn.setRequestProperty("Connection", "Keep-Alive");
        conn.setUseCaches(false);
        conn.setDoOutput(true);
        conn.setDoInput(true);
        // 获取URLConnection对象对应的输出流
        out = new OutputStreamWriter(conn.getOutputStream(), "UTF-8");
        // 发送请求参数
        out.write(param);
        out.flush();
        // 定义BufferedReader输入流来读取URL的响应
        in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
        String line;
        while ((line = in.readLine()) != null) {
            result.append(line);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            if (out != null) {
                out.close();
            }
            if (in != null) {
                in.close();
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
    return result.toString();
}

2. 使用HttpClient发送POST请求

public static String sendPost(String url, Map<String, String> params) {
    CloseableHttpClient httpClient = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost(url);
    CloseableHttpResponse response = null;
    String result = "";
    try {
        List<NameValuePair> list = new ArrayList<>();
        for (Map.Entry<String, String> entry : params.entrySet()) {
            list.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
        }
        httpPost.setEntity(new UrlEncodedFormEntity(list, "UTF-8"));
        response = httpClient.execute(httpPost);
        HttpEntity entity = response.getEntity();
        if (entity != null) {
            result = EntityUtils.toString(entity, "UTF-8");
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            if (response != null) {
                response.close();
            }
            httpClient.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return result;
}

以上两种方法都可以用来发送POST请求，具体使用哪种方法可以根据实际情况来选择。