java - 上传大文件时暂停/恢复 Httpurl 连接 - Android

Question

我能够使用 httpurlconnection 使用 .setChunkedstreamingmode() 将大文件(测试高达 1.2GB)上传到服务器。我了解到我们必须保持 url 连接有效才能发送大文件。我用来上传大文件的代码是，

public static String uploadFileToServer(String filename, String targetUrl) {
        String response = "error";
        HttpURLConnection connection = null;
        DataOutputStream outputStream = null;

        String pathToOurFile = filename;
        String urlServer = targetUrl;
        String lineEnd = "\r\n";
        String twoHyphens = "--";
        String boundary = "*****";

        int bytesRead, bytesAvailable, bufferSize;
        byte[] buffer;
        int maxBufferSize = 1 * 1024;
        try {
            FileInputStream fileInputStream = new FileInputStream(new File(
                    pathToOurFile));

            URL url = new URL(urlServer);
            connection = (HttpURLConnection) url.openConnection();

            // Allow Inputs & Outputs
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setUseCaches(false);
            connection.setChunkedStreamingMode(1024);
            // Enable POST method
            connection.setRequestMethod("POST");

            connection.setRequestProperty("Connection", "Keep-Alive");
            connection.setRequestProperty("Content-Type",
                    "multipart/form-data; boundary=" + boundary);

            outputStream = new DataOutputStream(connection.getOutputStream());
            outputStream.writeBytes(twoHyphens + boundary + lineEnd);

            String token = "anyvalye";
            outputStream.writeBytes("Content-Disposition: form-data; name=\"Token\"" + lineEnd);
            outputStream.writeBytes("Content-Type: text/plain;charset=UTF-8" + lineEnd);
            outputStream.writeBytes("Content-Length: " + token.length() + lineEnd);
            outputStream.writeBytes(lineEnd);
            outputStream.writeBytes(token + lineEnd);
            outputStream.writeBytes(twoHyphens + boundary + lineEnd);

            String taskId = "anyvalue";
            outputStream.writeBytes("Content-Disposition: form-data; name=\"TaskID\"" + lineEnd);
            outputStream.writeBytes("Content-Type: text/plain;charset=UTF-8" + lineEnd);
            outputStream.writeBytes("Content-Length: " + taskId.length() + lineEnd);
            outputStream.writeBytes(lineEnd);
            outputStream.writeBytes(taskId + lineEnd);
            outputStream.writeBytes(twoHyphens + boundary + lineEnd);

            String connstr = null;
            connstr = "Content-Disposition: form-data; name=\"UploadFile\";filename=\""
                    + pathToOurFile + "\"" + lineEnd;

            outputStream.writeBytes(connstr);
            outputStream.writeBytes(lineEnd);

            bytesAvailable = fileInputStream.available();
            bufferSize = Math.min(bytesAvailable, maxBufferSize);
            buffer = new byte[bufferSize];

            // Read file
            bytesRead = fileInputStream.read(buffer, 0, bufferSize);
            System.out.println("Image length " + bytesAvailable + "");
            try {
                while (bytesRead > 0) {
                    try {
                        outputStream.write(buffer, 0, bufferSize);
                    } catch (OutOfMemoryError e) {
                        e.printStackTrace();
                        response = "outofmemoryerror";
                        return response;
                    }
                    bytesAvailable = fileInputStream.available();
                    bufferSize = Math.min(bytesAvailable, maxBufferSize);
                    bytesRead = fileInputStream.read(buffer, 0, bufferSize);
                }
            } catch (Exception e) {
                e.printStackTrace();
                response = "error";
                return response;
            }
            outputStream.writeBytes(lineEnd);
            outputStream.writeBytes(twoHyphens + boundary + twoHyphens
                    + lineEnd);

            // Responses from the server (code and message)
            int serverResponseCode = connection.getResponseCode();
            String serverResponseMessage = connection.getResponseMessage();
            System.out.println("Server Response Code " + " " + serverResponseCode);
            System.out.println("Server Response Message "+ serverResponseMessage);

            if (serverResponseCode == 200) {
                response = "true";
            }else
            {
                response = "false";
            }

            fileInputStream.close();
            outputStream.flush();

            connection.getInputStream();
            //for android InputStream is = connection.getInputStream();
            java.io.InputStream is = connection.getInputStream();

            int ch;
            StringBuffer b = new StringBuffer();
            while( ( ch = is.read() ) != -1 ){
                b.append( (char)ch );
            }

            String responseString = b.toString();
            System.out.println("response string is" + responseString); //Here is the actual output

            outputStream.close();
            outputStream = null;

        } catch (Exception ex) {
            // Exception handling
            response = "error";
            System.out.println("Send file Exception" + ex.getMessage() + "");
            ex.printStackTrace();
        }
        return response;
    }

现在在我的上传过程中，如果我暂停上传并继续，那么它会从第一个字节开始，而不是计算服务器接收到的 block 。为了克服这个问题，我编码为

// Initial download.
    String lastModified = connection.getHeaderField("Last-Modified");

// Resume Upload.
connection.setRequestProperty("If-Range", lastModified);

但我无法恢复上传过程。任何人都可以在这个问题上帮助我，因为我是新学习这个概念的。提前致谢。

Answer 1

如果接收服务器支持，您可以使用 Content-Range header 来标识恢复上传。 Google-Drive API 支持它。如果您自己推出，我会遵循 Google 使用的模式:

• 开始上传并获取 session 标识符。
• 上传中断时，请等待互联网恢复可用。
• 恢复上传时，首先向服务器查询它收到了多少字节。 (*)
• 在服务器状态后的下一个字节恢复上传。

(*) 请注意，当我之前自己滚动时，我添加了来自服务器的编码响应以及上传的最后 KB，只是为了验证它在传输过程中没有损坏。但是，在生产中，我从未见过服务器收到损坏数据的情况。