我正在尝试发送一个包含大型图像文件的multipart/form-data POST请求。我无法预先将文件转换为字节数组，否则我的应用程序会崩溃并出现OutOfMemory异常，因此我必须直接将文件内容写入连接的outputstream中。此外，我的服务器不支持分块模式，因此在发送数据之前必须计算内容长度，并使用连接的setFixedLengthStreamingMode方法。
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, 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);
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
}
}
很不幸，我的应用在 outputStream.close() 处崩溃并抛出 IOException 异常，我不知道原因是什么：
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)