所以我正在尝试发送带有大图像文件的multipart / form-data POST请求.我不能预先将文件转换为字节数组,我的应用程序会因OutOfMemory异常而崩溃,所以我必须将文件的内容直接写入连接的输出流.此外,我的服务器不支持分块模式,因此我必须在发送数据之前计算内容长度并使用连接的setFixedLengthStreamingMode.

public void createImagePostWithToken(String accessToken,String text,String type,String imagePath) {

    URL imageUrl = null;
    String lineEnd = "\r\n";
    String twoHyphens = "--";

    // generating byte[] boundary here

    HttpURLConnection conn = null;
    DataOutputStream outputStream = null;
    DataInputStream inputStream = null; 

    int bytesRead,bytesAvailable,bufferSize;
    byte[] buffer;
    int maxBufferSize = 1*1024*1024;

    try
    {
        long contentLength;
        int serverResponseCode;
        String serverResponseMessage;
        File file = new File(imagePath);            
        FileInputStream fileInputStream = new FileInputStream(file);
        imageUrl = buildUri("posts").toURL();
        conn = (HttpURLConnection)imageUrl.openConnection();
        conn.setConnectTimeout(30000);
        conn.setReadTimeout(30000);
        conn.setDoOutput(true);
        conn.setDoInput(true);         
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Content-Type","multipart/form-data;boundary=" + boundary);            

        String stringForLength = new String();  

        stringForLength += "Content-Type: multipart/form-data;boundary=" + boundary;

        stringForLength += twoHyphens + boundary + lineEnd + "Content-Disposition: form-data; name=\"access_token\"" + lineEnd;
        stringForLength += "Content-Type: text/plain;charset=UTF-8" + lineEnd + "Content-Length: " + accessToken.length() + lineEnd + lineEnd;
        stringForLength += accessToken + lineEnd + twoHyphens + boundary + lineEnd;

        stringForLength += "Content-Disposition: form-data; name=\"text\"" + lineEnd;
        stringForLength += "Content-Type: text/plain;charset=UTF-8" + lineEnd + "Content-Length: " + text.length() + lineEnd + lineEnd;
        stringForLength += text + lineEnd + twoHyphens + boundary + lineEnd;

        stringForLength += "Content-Disposition: form-data; name=\"type\"" + lineEnd;
        stringForLength += "Content-Type: text/plain;charset=UTF-8" + lineEnd + "Content-Length: " + type.length() + lineEnd + lineEnd;
        stringForLength += type + lineEnd + twoHyphens + boundary + lineEnd;

        stringForLength += twoHyphens + boundary + lineEnd + "Content-Disposition: form-data; name=\"image\"" + lineEnd;
        stringForLength += "Content-Type: application/octet-stream" + lineEnd + "Content-Length: " + file.length() + lineEnd + lineEnd;
        stringForLength += lineEnd + twoHyphens + boundary + twoHyphens + lineEnd;

        int totalLength = stringForLength.length() + (int)file.length();           
        conn.setFixedLengthStreamingMode(totalLength); 


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

        // access token 

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

        // text 

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

        // type 

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

        // image

        outputStream.writeBytes(twoHyphens + boundary + lineEnd);
        outputStream.writeBytes("Content-Disposition: form-data; name=\"image\"" + lineEnd);
        //outputStream.writeBytes(lineEnd);
        outputStream.writeBytes("Content-Type: application/octet-stream" + lineEnd);
        outputStream.writeBytes("Content-Length: " + file.length() + lineEnd);
        outputStream.writeBytes(lineEnd);           

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

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

        outputStream.writeBytes(lineEnd);
        outputStream.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);

        Log.d("posttemplate","connection outputstream size is " + outputStream.size());

        // finished with POST request body


     // Responses from the server (code and message)
        serverResponseCode = conn.getResponseCode();
        serverResponseMessage = conn.getResponseMessage();

        Log.d("posttemplate","server response code "+ serverResponseCode);
        Log.d("posttemplate","server response message "+ serverResponseMessage);

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


    } catch (MalformedURLException e)
    {
        Log.d("posttemplate","malformed url",e);
        //TODO: catch exception;
    } catch (IOException e)
    {
        Log.d("posttemplate","ioexception",e);
        //TODO: catch exception
    }        

}

不幸的是,我的应用程序在outputStream.close()时崩溃了IOException,我不明白为什么：

03-16 13:56:51.035: D/posttemplate(6479): java.io.IOException: unexpected end of stream
03-16 13:56:51.035: D/posttemplate(6479):   at org.apache.harmony.luni.internal.net.www.protocol.http.FixedLengthOutputStream.close(FixedLengthOutputStream.java:57)
03-16 13:56:51.035: D/posttemplate(6479):   at java.io.FilterOutputStream.close(FilterOutputStream.java:66)
03-16 13:56:51.035: D/posttemplate(6479):   at com.futubra.api.impl.PostTemplate.createImagePostWithToken(PostTemplate.java:282)
03-16 13:56:51.035: D/posttemplate(6479):   at com.futubra.FutubraNewPostActivity.createPost(FutubraNewPostActivity.java:128)
03-16 13:56:51.035: D/posttemplate(6479):   at com.futubra.FutubraNewPostActivity_.access$2(FutubraNewPostActivity_.java:1)
03-16 13:56:51.035: D/posttemplate(6479):   at com.futubra.FutubraNewPostActivity_$5.run(FutubraNewPostActivity_.java:141)
03-16 13:56:51.035: D/posttemplate(6479):   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
03-16 13:56:51.035: D/posttemplate(6479):   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
03-16 13:56:51.035: D/posttemplate(6479):   at java.lang.Thread.run(Thread.java:1019)