java - 使用 httpurlconnection multipart/form-data 上传数组列表

Question

我需要上传Arraylist无需使用任何库即可将图像发送到服务器。我正在使用 Asynctask上传单个图像，它在 httpurlconnection multipart/form-data 的帮助下完美运行。现在我需要更改我的代码以使用 Arraylist<String> 上传任何类型的多个文件但我的问题是现有代码的 FileinputStream不支持arraylist，我不知道用什么代替Fileinputstream将arraylist上传到服务器，我也不想为此使用任何库。

public class multipart_test extends AsyncTask<Void,Void,String> {
    Context context;
    String Images;
    public static final String TAG = "###Image Uploading###";


    public multipart_test(Context context,String Upload_Images) {
        this.context = context;
        this.Images = Upload_Images;

    }

    @Override
    protected String doInBackground(Void... params) {
        BufferedReader reader;
        String WebPath = null;
        try {
            String lineEnd = "\r\n";
            String twoHyphens = "--";
            String boundary = "*****";
            int bytesRead, bytesAvailable, bufferSize;
            byte[] buffer;
            int maxBufferSize = 1024 * 1024;
            //todo change URL as per client ( MOST IMPORTANT )
            URL url = new URL("10.0.0.1/uploadMultipart.php");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();

            // Allow Inputs &amp; Outputs.
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setUseCaches(false);

            // Set HTTP method to POST.
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Connection", "Keep-Alive");
            connection.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);
            FileInputStream fileInputStream;
            DataOutputStream outputStream;
            outputStream = new DataOutputStream(connection.getOutputStream());
            outputStream.writeBytes(twoHyphens + boundary + lineEnd);

            outputStream.writeBytes("Content-Disposition: form-data; name=\"reference\""+ lineEnd);
            outputStream.writeBytes(lineEnd);
            //outputStream.writeBytes("my_refrence_text");
            outputStream.writeBytes(lineEnd);
            outputStream.writeBytes(twoHyphens + boundary + lineEnd);

            outputStream.writeBytes("Content-Disposition: form-data; name=\"uploadFile\";filename=\"" + "profileImage" +"\"" + lineEnd);
            outputStream.writeBytes(lineEnd);

            //Dummy ArrayList for upload
            ArrayList<String> uploadFiles = new ArrayList<>();
            uploadFiles.add(Images);
            uploadFiles.add(Images);
            uploadFiles.add(Images);
            uploadFiles.add(Images);


            fileInputStream = new FileInputStream(uploadFiles); // NOT SUPPORTING ARRAYLIST HERE
            bytesAvailable = fileInputStream.available();
            bufferSize = Math.min(bytesAvailable, maxBufferSize);
            buffer = new byte[bufferSize];

            // Read file
            bytesRead = fileInputStream.read(buffer, 0, bufferSize);

            while (bytesRead > 0) {
                outputStream.write(buffer, 0, bufferSize);
                bytesAvailable = fileInputStream.available();
                bufferSize = Math.min(bytesAvailable, maxBufferSize);
                bytesRead = fileInputStream.read(buffer, 0, bufferSize);

            outputStream.writeBytes(lineEnd);
            outputStream.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);
                fileInputStream.close();
            }
            // Responses from the server (code and message)
            int serverResponseCode = connection.getResponseCode();
            String result = null;
            if (serverResponseCode == 200) {
                StringBuilder s_buffer = new StringBuilder();
                InputStream is = new BufferedInputStream(connection.getInputStream());
                BufferedReader br = new BufferedReader(new InputStreamReader(is));
                String inputLine;
                while ((inputLine = br.readLine()) != null) {
                    s_buffer.append(inputLine);
                }
                result = s_buffer.toString();
            }
            connection.getInputStream().close();
            outputStream.flush();
            outputStream.close();
            if (result != null) {
                Log.d("result_for upload", result);
            }
            return WebPath;
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }


}

我也试着把 FileInputStream进入循环，但将图像上传到多个请求不是我想要的。我的服务器要求应用程序对 n 个图像发出单个请求。任何帮助将不胜感激，但不使用任何库

Answer 1

请注意，如果此代码确实适用于 HttpURLConnection，我还没有尝试过，但它应该。

根据我从互联网上读到的内容，您仍然可以使用您提到的那个循环，但需要进行一些修改。

我在这里遵循了关于 multipart/form-data 的教程 dev.to ，为了让这篇文章更像是一篇学习文章，我会告诉你这个方法应该发生什么。

multipart/form-data 是这样发送的

--boundary
Content-Disposition: form-data; name="something1"

data1
--boundary
Content-Disposition: form-data; name="something2"

data2
--boundary--

我要做的是创建一个新方法，但您可以在现有方法中编写代码。

public byte[] get_multipart_data(List<String> files, String boundary)

您要写的是边界，然后是处置，然后是数据。对所有文件执行此操作，然后发送关闭边界。这将生成您想要的 multipart/form-data 结构。

在伪代码中，这将是

loop for all files
    write "--boundary"
    write "Content-Disposition: ...."
    write image_data
end
write "--boundary--"

代码可以这样写，首先你定义你的变量

ByteArrayOutputStream message = null;
DataOutputStream stream = null;

FileInputStream fileInputStream;

int maxBufferSize = 1024 * 1024;
byte[] buffer = new byte[maxBufferSize];
byte[] sendData = new byte[0];

这里是生成数据的地方。
它从连接边界开始，然后读取数据。该数据被写入流中，然后您继续循环所有文件/图像。

try {
    message = new ByteArrayOutputStream();
    stream = new DataOutputStream(message);

    // Loop though all file names
    for(String fileName : files) {
        stream.writeBytes("--" + boundary + "\r\n"); // Start boundary
        stream.writeBytes("Content-Disposition: form-data; name=\"" + fileName + "\"\r\n\r\n");

        // Read the image data
        fileInputStream = new FileInputStream(fileName);
        int readBytes = 0;
        while((readBytes = fileInputStream.read(buffer)) != -1) {
            // Write file data to output
            stream.write(buffer, 0, readBytes);
        }
        fileInputStream.close();

        stream.writeBytes("\r\n");
    }
    stream.writeBytes("--" + boundary + "--\r\n"); // Closing boundary

    sendData = message.toByteArray();
} catch(IOException e) {
    e.printStackTrace();
}

现在字节数组 sendData将包含您需要与 HttpURLConnection 一起发送的 multipart/form-data。

我已经很久没有在这里那么活跃了。告诉我您是否需要更多规范或我澄清我的文字:D