Android HttpURLConnect POST Stream Size

Question

我正在尝试按照这里的教程进行操作 https://developer.android.com/reference/java/net/HttpURLConnection.html

在安卓中拨打邮局电话。我遇到的问题是我不确定如何将 post 调用写入 http 连接。

URL url = new URL("https://chart.googleapis.com/chart");
            HttpURLConnection client = null;
            client = (HttpURLConnection) url.openConnection();
            client.setRequestMethod("POST");
            client.setRequestProperty("cht", "lc");
            client.setRequestProperty("chtt", "This is | my chart");
            client.setRequestProperty("chs", "300x200");
            client.setRequestProperty("chxt", "x");
            client.setRequestProperty("chd", "t:40,20,50,20,100");
            client.setDoOutput(true);
            client.setChunkedStreamingMode(0);
            OutputStream outputPost = new BufferedOutputStream(client.getOutputStream());
            outputPost.write(client.getRequestProperties().toString().getBytes());
            outputPost.flush();
            outputPost.close();
            InputStream in = new BufferedInputStream(client.getInputStream());
            Log.d(TAG, "Input" + in.read());
            client.disconnect();
        } catch (MalformedURLException error) {
            //Handles an incorrectly entered URL
            Log.d(TAG, "MalformedURL");
        } catch (SocketTimeoutException error) {
//Handles URL access timeout.
            Log.d(TAG, "Socket Timeout");
        } catch (IOException error) {
//Handles input and output errors
            Log.d(TAG, "IOexception");
        }

本教程使用自定义方法来写入流，但我仍然遇到为 POST 正文写入未知数量的字节。

Answer 1

需要考虑的问题：

1. 谷歌图表 API 是否要求通过标头变量发送信息？
2. Google 图表 API 是否需要在正文中发送信息？
3. 正文中的信息是否以正确的格式发送？
4. 缺少内容类型标头变量
5. 为什么在标头和正文中设置相同的数据？

阅读谷歌图表

指南后，以下代码将成功向谷歌图表API发出POST请求，并以字节形式检索图像。

若要编写发布数据，请参阅 getImage 代码示例中的以下行：con.getOutputStream().write(postDataBytes);

请注意以下行以设置帖子大小：con.setRequestProperty("Content-Length", String.valueOf(postDataBytes.length));

  public byte[] getImage() throws IOException {
    URL obj = new URL("https://chart.googleapis.com/chart");
    HttpURLConnection con = (HttpURLConnection) obj.openConnection();
    // Store the post data
    Map<String,Object> params = new LinkedHashMap<>();
    params.put("cht", "lc");
    params.put("chtt", "This is | my chart");
    params.put("chs", "300x200");
    params.put("chxt", "x");
    params.put("chd", "t:40,20,50,20,100");
    // Build the post data into appropriate format
    StringBuilder postData = new StringBuilder();
    for (Map.Entry<String,Object> param : params.entrySet()) {
        if (postData.length() != 0) postData.append('&');
        postData.append(URLEncoder.encode(param.getKey(), "UTF-8"));
        postData.append('=');
        postData.append(URLEncoder.encode(String.valueOf(param.getValue()), "UTF-8"));
    }
    byte[] postDataBytes = postData.toString().getBytes("UTF-8");
    con.setRequestMethod("POST");
    con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
    con.setRequestProperty("Content-Length", String.valueOf(postDataBytes.length));
    con.setDoOutput(true);
    // post the data
    con.getOutputStream().write(postDataBytes);
    // opens input stream from the HTTP connection
    InputStream inputStream = con.getInputStream();
    // read the data from response
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    byte[] byteChunk = new byte[4096]; // Or whatever size you want to read in at a time.
    int n;
    while ( (n = inputStream.read(byteChunk)) > 0 ) {
        baos.write(byteChunk, 0, n);
    }
    inputStream.close();
    return baos.toByteArray();
}