我已经能够使用Christian d’Heure的this库将文件转换为Base64字符串,以字节为单位计算字符串的大小并将其先前发送,但我之前使用的方法包括将整个文件加载到内存中.处理大文件时导致内存不足错误,这并不意外.

我一直在尝试将文件转换为块中的Base64并在转换时通过连接(使用数据输出流对象)传输此数据,因此整个文件不需要一次性加载到内存中,在转换文件之前,我似乎无法准确计算出请求的Content-Length的大小 – 我通常看起来大概是10个字节 – 令人沮丧的是,它偶尔会起作用！

我还发现,有些时候,这确实有效,服务器返回以下错误消息“Base64 char数组的大小无效”.我认为这是一个填充字符的问题,但是我看不出我的代码有问题,这个问题的一些建议将非常感谢！

这是生成请求并流式传输数据的代码：

try
{


    HttpURLConnection connection = null;

    DataOutputStream outputStream = null;

    DataInputStream inputStream = null;

    //This is the path to the file
    String pathToOurFile = Environment
            .getExternalStorageDirectory().getPath()
            + "/path/to/the/file.zip";

    String urlServer = "https://www.someserver.com/somewebservice/";

    int bytesRead,bytesAvailable,bufferSize;

    byte[] buffer;

    int maxBufferSize = 456;


    //The parameters of the POST request - File Data is the file in question as a Base64 String
    String params = "Username=foo&Password=bar&FileData=";

    File sizeCheck = new File(pathToOurFile);

    Integer zipSize = (int) sizeCheck.length();

    Integer paddingrequired = ((zipSize * 8) / 6) % 3;

    Integer base64ZipSize = ((zipSize * 8) / 6)
            + ((zipSize * 8) / 6) % 3;

    Integer paramLength = params.getBytes().length;

    //Code to work out the number of lines required,assuming we create a new
    //line every 76 characters - this is used t work out the number of
    //extra bytes required for new line characters
    Integer numberOfLines = base64ZipSize / 76;

    Log.i(TAG,"numberOfLines: " + numberOfLines);

    Integer newLineLength = System.getProperty("line.separator")
            .getBytes().length;

    //This works out the total length of the Content
    Integer totalLength = paramLength + base64ZipSize
            + (numberOfLines * newLineLength) + paddingrequired;

    Log.i(TAG,"total Length: " + totalLength);

    FileInputStream fileInputStream = new FileInputStream(new File(
            pathToOurFile));

    URL url = new URL(urlServer);

    connection = (HttpURLConnection) url.openConnection();

    connection.setDoInput(true);

    connection.setDoOutput(true);

    connection.setUseCaches(false);

    connection.setRequestMethod("POST");

    connection.setRequestProperty("Connection","Keep-Alive");

    connection.setRequestProperty("Content-Type","application/x-www-form-urlencoded;");

    connection.setRequestProperty("Content-Length",""
            + totalLength); // number of bytes

    outputStream = new DataOutputStream(
            connection.getoutputStream());

    //Write out the parameters to the data output stream
    outputStream.writeBytes(params);

    bytesAvailable = fileInputStream.available();

    bufferSize = Math.min(bytesAvailable,maxBufferSize);

    buffer = new byte[bufferSize];

    bytesRead = fileInputStream.read(buffer,bufferSize);

    Integer totalSent = paramLength;

    Integer enLen = 0;


    //Convert the file to Base64 and Stream the result to the
    //Data output stream
    while (bytesRead > 0)
    {
        String convetedBase64 = Base64Coder.encodeLines(buffer);
        convetedBase64 = convetedBase64.replace("=","");

        if (totalSent >= (totalLength - 616))
        {
            Log.i(TAG,"about to send last chunk of data");
            convetedBase64 = convetedBase64.substring(0,convetedBase64.length() - 1);
        }

        Log.i(TAG,"next data chunk to send: "
                        + convetedBase64.getBytes().length);
        Log.i(TAG,"''" + convetedBase64 + "''");

        enLen = enLen + convetedBase64.length();
        outputStream.writeBytes(convetedBase64);

        totalSent = totalSent + convetedBase64.getBytes().length;

        Log.i(TAG,"total sent " + totalSent);
        Log.i(TAG,"actual size: " + outputStream.size());

        bytesAvailable = fileInputStream.available();
        bufferSize = Math.min(bytesAvailable,maxBufferSize);
        buffer = new byte[bufferSize];
        bytesRead = fileInputStream.read(buffer,bufferSize); // read
                                                                    // into
                                                                    // the
                                                                    // buffer
    }

    Log.i(TAG,"enLen: " + enLen);
    Log.i(TAG,"paddingrequired: " + paddingrequired);

    for (int x = 0; x < paddingrequired; x++)
    {
        outputStream.writeBytes("=");
    }

    InputStream is2 = connection.getInputStream();
    String output = IoUtils.toString(is2);
    Log.i(TAG,"Got server response: " + output);
    fileInputStream.close();
    outputStream.flush();
    outputStream.close();
}
catch (Exception ex)
{
    Log.e(TAG,"caught an exception:" + ex.getMessage());
}

如果有人能指出我的代码中可能导致此错误的任何错误,或者建议更好的转换和上传文件的方式,我将非常感激.

第一个是将数据写入一个临时文件,所以我可以在转换后以字节为单位获得大小 – 一开始似乎是一个好主意,但效率低下并且在发现其他方法之后似乎很愚蠢.

另一种方法是不指定内容长度(我不知道你可以这样做！).不幸的是,Android仍然试图为上传分配足够的内存,这导致了问题.

如果你指定连接使用ChunkedStreamingMode Android然后播放不错并缓冲上传,节省使用的ram(除了2.2上的一个奇怪的bug).

这样的代码是这样的：

httppost.setDoInput(true);
httppost.setDoOutput(true);
httppost.setRequestMethod("POST");
httppost.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
httppost.setChunkedStreamingMode(0); //This specifies the size of the chunks - 0 uses the system default

DataOutputStream dos = new DataOutputStream(httppost.getoutputStream());
dos.writeBytes(content); //This code write out the rest of the post body first,for example username or password

try
{
    BufferedInputStream dis = new BufferedInputStream(new FileInputStream("path/to/some/file"),2048);

    byte[] in = new byte[512];

    while (dis.read(in)) > 0)
    {
        dos.write(Base64.encode(in,Base64.URL_SAFE)); //This writes out the Base64 data
                                                       //I used the web safe base64 to save URL encoding it again
                                                       //However your server must support this
        dos.write(newLine); //this write out a newline character
    }

dos.flush();
dis.close();
dos.close();

我希望这有帮助！！！