Develop Reference

How to write a file to an HTTP Request Java

I am new to using HTTP and I have questions about writing a file and another value to an HTTP Post request in Java. I am using an public API provided by a company called Mojang to write what is known as a "skin" (a png file) to the game Minecraft for player character modles. Here is the documentation of how to use this public API for reference:https://wiki.vg/Mojang_API#Upload_Skin
Here is the code I have written. When ran I get the 415 HTTP Response code (which I assume is "unsupported media type"). Any suggestions on what I am doing wrong and how I can fix this? I found other stack overflow issues for uploading files but I need to also add a value called "variant={classic or slim}". I am a little lost on how to make all of this work. Any help is much appreciated.
(I could not get the code to properally format in the code sample using ' ', it is in a javascript snippet)
public static void uploadSkin(String accessToken, String variant, File file) throws IOException {
URL url = new URL("https://api.minecraftservices.com/minecraft/profile/skins");
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setDoOutput(true);
con.setRequestMethod("POST");
con.setRequestProperty("Authorization", "Bearer " + accessToken); // The access token is provided after an
// authentication request has been send, I
// have done this sucessfully in another
// method and am passing it in here
con.addRequestProperty("variant", variant);
OutputStream outputStream = con.getOutputStream();
PrintWriter writer = new PrintWriter(new OutputStreamWriter(con.getOutputStream(), "utf-8"), true);
String boundary = "===" + System.currentTimeMillis() + "===";
String fileName = file.getName();
String LINE_FEED = "\r\n";
String fieldName = "file";
writer.append("--" + boundary).append(LINE_FEED);
writer.append("Content-Disposition: form-data; name=\"" + fieldName + "\"; filename=\"" + fileName + "\"")
.append(LINE_FEED);
writer.append("Content-Type: " + URLConnection.guessContentTypeFromName(fileName)).append(LINE_FEED);
writer.append("Content-Transfer-Encoding: binary").append(LINE_FEED);
writer.append(LINE_FEED);
writer.flush();
FileInputStream inputStream = new FileInputStream(file);
byte[] buffer = new byte[4096];
int bytesRead = -1;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.flush();
inputStream.close();
writer.append(LINE_FEED);
writer.flush();
}

Alright, found a solution to the problem. Using this maven dependency:
<!-- https://mvnrepository.com/artifact/org.jodd/jodd-http -->
<dependency>
<groupId>org.jodd</groupId>
<artifactId>jodd-http</artifactId>
<version>5.0.2</version>
</dependency>
And then this:
HttpResponse response = HttpRequest.post("https://api.minecraftservices.com/minecraft/profile/skins")
.header("Authorization", "Bearer " + accessToken).header("Content-Type", "multipart/form-data")
.form("variant", variant).form("file", file).send();
I was able to get it to work. Hope this is helpful to anyone that needs to upload a Skin Png file to Minecraft.

How to download a part of a file from URL in android?

I am trying to download a part of file given the download URL using setRequestProperty("Range","bytes=" + startbytes + "-" + endbytes); The following code snippet shows what I am trying to do.
protected String doInBackground(String... aurl) {
int count;
Log.d(TAG,"Entered");
try {
URL url = new URL(aurl[0]);
HttpURLConnection connection =(HttpURLConnection) url.openConnection();
int lengthOfFile = connection.getContentLength();
Log.d(TAG,"Length of file: "+ lengthOfFile);
connection.setRequestProperty("Range", "bytes=" + 0 + "-" + 1000);
The problem is that, an exception is being raised, which says "Cannot set request property after connection is made". Please help me resolve this issue.

Option 1
If you do not need to know the content length:
[Beware, do not call the connection.getContentLength(). If you call that, you will get the exception. If you need to call it, then check the second option]
URL url = new URL(aurl[0]);
HttpURLConnection connection =(HttpURLConnection) url.openConnection();
connection.setRequestProperty("Range", "bytes=" + 0 + "-" + 1000);
//Note that, response code will be 206 (Partial Content) instead of usual 200 (OK)
if(connection.getResponseCode() == HttpURLConnection.HTTP_PARTIAL){
//Your code here to read response data
}
Option 2
If you need to know the content length:
URL url = new URL(aurl[0]);
//First make a HEAD call to get the content length
HttpURLConnection connection =(HttpURLConnection) url.openConnection();
connection.setRequestMethod("HEAD");
if(connection.getResponseCode() == HttpURLConnection.HTTP_OK){
int lengthOfFile = connection.getContentLength();
Log.d("ERF","Length of file: "+ lengthOfFile);
connection.disconnect();
//Now that we know the content lenght, make the GET call
connection =(HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setRequestProperty("Range", "bytes=" + 0 + "-" + 1000);
//Note that, response code will be 206 (Partial Content) instead of usual 200 (OK)
if(connection.getResponseCode() == HttpURLConnection.HTTP_PARTIAL){
//Your code here to read response data
}
}

Assuming you're using HTTP for the download, you'll want to use the HEAD http verb and RANGE http header.
HEAD will give you the filesize (if available), and then RANGE lets you download a byte range.
Once you have the filesize, divide it into roughly equal sized chunks and spawn download thread for each chunk. Once all are done, write the file chunks in the correct order.
If you don't know how to use the RANGE header, here's another SO answer that explains how: https://stackoverflow.com/a/6323043/1355166
[EDIT]
To make file into chunks use this, and start the downloading process,
private void getBytesFromFile(File file) throws IOException {
FileInputStream is = new FileInputStream(file); //videorecorder stores video to file
java.nio.channels.FileChannel fc = is.getChannel();
java.nio.ByteBuffer bb = java.nio.ByteBuffer.allocate(10000);
int chunkCount = 0;
byte[] bytes;
while(fc.read(bb) >= 0){
bb.flip();
//save the part of the file into a chunk
bytes = bb.array();
storeByteArrayToFile(bytes, mRecordingFile + "." + chunkCount);//mRecordingFile is the (String)path to file
chunkCount++;
bb.clear();
}
}
private void storeByteArrayToFile(byte[] bytesToSave, String path) throws IOException {
FileOutputStream fOut = new FileOutputStream(path);
try {
fOut.write(bytesToSave);
}
catch (Exception ex) {
Log.e("ERROR", ex.getMessage());
}
finally {
fOut.close();
}
}

How to disable buffering in Java HttpURLConnection for multi-part form post?

(This is for a signed applet and I have decided against HTTPClient to keep my jar very small)
I am using HttpURLConnection to successfully upload a file from the user to a server using multi-part form post.
The problem is that HttpURLConnection is caching the data -- before sending it. So when I am reading from the file and writing to Outputstream, it is merely buffering the data -- and therefore my progress bar, that shows the upload status , is completely wrong. Howevere please note that the form post code works and the file does get uploaded correctly with return code of 200.
So how do I ensure that HttpURLConnection does not cache the data that I am sending to the server ?
Here is my source:
public UploadResponse send(String formPostUrlStr,String fileFieldName,File targetFile, Map<String, String> valuesMap, UploadStatusListener uploadStatusListener) throws Exception{
String sendStr=getBoundaryMessage(Boundary, valuesMap, fileFieldName, targetFile.getName(), valuesMap.get("content-type") );//"image/png") ;
System.out.println(" multi-part start \n "+ sendStr+ " multi-part end \n");
String lenstr=Long.toString((long)(sendStr.length()*2)+ targetFile.length());
System.out.println("Content-Length"+ lenstr);
//Content-Length
URL url= new URL(formPostUrlStr);
long startTime= System.currentTimeMillis();
HttpURLConnection s3Connection = (HttpURLConnection) url.openConnection();
System.out.println("opened url to "+ formPostUrlStr +", connection ok ..");
s3Connection.setRequestProperty("Content-Type", "multipart/form-data; boundary="
+ Boundary);
s3Connection.setRequestProperty("content-length", lenstr);
s3Connection.setDoOutput(true);
s3Connection.setDoInput(true);
s3Connection.setUseCaches(false);
s3Connection.setInstanceFollowRedirects(true);
s3Connection.setAllowUserInteraction(true);
s3Connection.setRequestProperty("User-Agent", "Mozilla/4.5");
if (uploadStatusListener != null) {
uploadStatusListener.statusUpdate(targetFile.length(), 0);
}
String debugStr= s3Connection.toString();
System.out.println("conmnection "+ debugStr);
DataOutputStream httpOut = new DataOutputStream(s3Connection.getOutputStream());
System.out.println("opened DataOutputStream ok ..");
httpOut.write(sendStr.getBytes());
//httpOut.flush();
System.out.println("httpOut.flush 1 ok ..");
FileInputStream uploadFileReader = new FileInputStream(targetFile);
long totalBytes = uploadFileReader.available();
if (uploadStatusListener != null) {
uploadStatusListener.statusUpdate(totalBytes, 0);
}
System.out.println(" uploading file with size "+ uploadFileReader.available());
int bufSize = 102400;
long availableBytesToRead;
long totalSent = 0;
while ((availableBytesToRead = uploadFileReader.available()) > 0) {
byte[] bufferBytesRead;
bufferBytesRead = availableBytesToRead >= bufSize ? new byte[bufSize]
: new byte[(int)availableBytesToRead];
int count = uploadFileReader.read(bufferBytesRead);
try{
httpOut.write(bufferBytesRead);
totalSent += ((long) count);
System.out.println(" wrote bytes = "+count+ ", total sent = "+ totalSent +", pendingSize"+ (availableBytesToRead-count) );
}
catch(IOException ioe){
System.out.println(" io exceotion e"+ ioe.getMessage());
throw ioe;
}
//httpOut.flush();
if (uploadStatusListener != null) {
uploadStatusListener.statusUpdate(totalBytes, totalSent);
}
}
// FILE DATA END
httpOut.write(("--" + Boundary + "--\r\n").getBytes());
// form end
httpOut.write(("--" + Boundary + "--\r\n").getBytes());
httpOut.flush();
httpOut.close();
long endTime= System.currentTimeMillis();
System.out.println("Completed Writing Data to S3 Connection in "+ (endTime-startTime)+"ms.,now waiting for rsponse code ");
int code=s3Connection.getResponseCode();
long endTime2= System.currentTimeMillis();
System.out.println("Completed Sendind Data to S3 in "+ (endTime2-startTime)+ "ms., rsponse code time "+ (endTime2-endTime)+"ms. ");
UploadResponse uploadResponse = new UploadResponse();
uploadResponse.setCode(code);
System.out.println(" response code : " + code);
StringBuilder response = new StringBuilder();
byte[] respBuffer = new byte[4096];
if (code > 300) {
if (code == 404) {
throw new Exception("Error 404");
}
BufferedReader err = new BufferedReader(
new InputStreamReader(s3Connection.getErrorStream()));
String ret;
StringBuffer buff = new StringBuffer();
while ((ret = err.readLine()) != null) {
buff.append(ret);
}
uploadResponse.setMessage(buff.toString());
System.out.println(" error :"+ buff.toString());
err.close();
} else {
BufferedReader inp = new BufferedReader(
new InputStreamReader(s3Connection.getInputStream()));
StringBuffer buff = new StringBuffer();
String ret;
while ((ret = inp.readLine()) != null) {
buff.append(ret);
}
inp.close();
uploadResponse.setMessage(buff.toString());
if(buff.toString().contains("fail"))
throw new Exception("Upload failed");
}
System.out.println(response.toString());
return uploadResponse;
}
}

I have the same problem.
I didn't find any other solution than writing my HTTP request on a raw Socket.
Did you find a better workaround ?
EDIT : I just did : we just have to use obj.setFixedLengthStreamingMode(12345) on the HttpURLConnection object obtained from url.openConnection(), where 12345 is the length of POST request body.

As a complementation for the answer that #Antares gave, there is another method setChunkedStreamingMode that is used when you don't know the content size in advance. So when you do a POST request, call that method on the connection:
HttpURLConnection connection = ...
connection.setRequestMethod("POST");
connection.setDoOutput(true);
connection.setChunkedStreamingMode(0);
connection.connect();
... connection.getOutputStream();
This will avoid the OutputStream to buffer the entire content before start to send.

Best approach: HTTP POST (multi-part) from Android to GAE

I would like to capture an image from the camera on Android, and send it to Google App Engine, which will store the image in the blob store. Sounds simple enough, and I can get the multi-part POST to GAE happening, but storing to the Blob store requires the servlet return an HTTP redirect (302). So, I need a connection that can follow redirects after doing an HTTP POST. Here is the code I WISH would work:
public static String sendPhoto(String myUrl, byte[] imageData) {
HttpURLConnection connection = null;
DataOutputStream outputStream = null;
String pathToOurFile = "/data/file_to_send.jpg";
String urlServer = myUrl;
String lineEnd = "\r\n";
String twoHyphens = "--";
String boundary = "*****";
// Please follow redirects
HttpURLConnection.setFollowRedirects(true);
BufferedReader rd = null;
StringBuilder sb = null;
String line = null;
try {
URL url = new URL(urlServer);
connection = (HttpURLConnection) url.openConnection();
// Allow Inputs & Outputs
connection.setDoInput(true);
connection.setDoOutput(true);
connection.setUseCaches(false);
// I really want you to follow redirects
connection.setInstanceFollowRedirects(true);
connection.setConnectTimeout(10000); // 10 sec
connection.setReadTimeout(10000); // 10 sec
// Enable POST method
connection.setRequestMethod("POST");
connection.setRequestProperty("Connection", "Keep-Alive");
connection.setRequestProperty("Content-Type",
"multipart/form-data;boundary=" + boundary);
connection.connect();
outputStream = new DataOutputStream(connection.getOutputStream());
outputStream.writeBytes(twoHyphens + boundary + lineEnd);
outputStream
.writeBytes("Content-Disposition: form-data; name="
+ "\"file1\";filename=\""
+ pathToOurFile + "\"" + lineEnd);
outputStream.writeBytes(lineEnd);
outputStream.write(imageData);
outputStream.writeBytes(lineEnd);
outputStream.writeBytes(twoHyphens + boundary + twoHyphens
+ lineEnd);
outputStream.flush();
outputStream.close();
rd = new BufferedReader(new InputStreamReader(
connection.getInputStream()));
sb = new StringBuilder();
while ((line = rd.readLine()) != null) {
sb.append(line + '\n');
}
Log.i("Response: ", sb.toString());
// Responses from the server (code and message)
int serverResponseCode = connection.getResponseCode();
String serverResponseMessage = connection.getResponseMessage();
Log.i("Response: serverResponseCode:",
String.valueOf(serverResponseCode));
Log.i("Response: serverResponseMessage:", serverResponseMessage);
} catch (Exception ex) {
ex.printStackTrace();
}
}
As much as I try, this code will not follow redirects. The input steam is always empty, and the response is always 302. The image is uploaded nicely though. If someone could tell me what I can do to make it follow the redirect so I can read the response, I would really appreciate it.
Alternatively, if there is a better approach, I would love to hear it. I know there are libraries out there like Apache HTTP Client, but it requires so many dependencies that is seems like too much bloat for a simple task.
Thanks

A few months ago I was trying to do the exact same thing!
Basically, don't use HttpURLConnection. Instead, use HttpClient and HttpGet in the org.apache.http package which are part of the Android SDK.
Unfortunately I don't have my source code to provide an example, but hopefully that'll set you in the right direction.

not sure what went wrong, but you can follow redirect yourself. take the Location header out and make a new connection to it.

Java applet to upload a file

I am looking for a Java applet to read a file from client machine and creat a POST request for PHP server uploading.
PHP script on server should receive the file as normal file upload in FORM submit.
I am using the following code. The file contents are passed to PHP script
but they are not correctly converted to an image.
//uploadURL will be a url of PHP script like
// http://www.example.com/uploadfile.php
URL url = new URL(uploadURL);
HttpURLConnection con = (HttpURLConnection)url.openConnection();
con.setRequestMethod("POST");
con.setDoInput(true);
con.setDoOutput(true);
InputStream is = new FileInputStream("C://img.jpg");
OutputStream os = con.getOutputStream();
byte[] b1 = new byte[10000000];
int n;
while((n = is.read(b1)) != -1) {
os.write("hello" , 0, 5);
test += b1;
}
con.connect();

Here is some code that might help you it's from one of my old projects with a bunch of unrelated stuff removed, take it for what it's worth. Basically, I think the code in your question is missing some parts that the HTTP protocol requires
public class UploaderExample
{
private static final String Boundary = "--7d021a37605f0";
public void upload(URL url, List<File> files) throws Exception
{
HttpURLConnection theUrlConnection = (HttpURLConnection) url.openConnection();
theUrlConnection.setDoOutput(true);
theUrlConnection.setDoInput(true);
theUrlConnection.setUseCaches(false);
theUrlConnection.setChunkedStreamingMode(1024);
theUrlConnection.setRequestProperty("Content-Type", "multipart/form-data; boundary="
+ Boundary);
DataOutputStream httpOut = new DataOutputStream(theUrlConnection.getOutputStream());
for (int i = 0; i < files.size(); i++)
{
File f = files.get(i);
String str = "--" + Boundary + "\r\n"
+ "Content-Disposition: form-data;name=\"file" + i + "\"; filename=\"" + f.getName() + "\"\r\n"
+ "Content-Type: image/png\r\n"
+ "\r\n";
httpOut.write(str.getBytes());
FileInputStream uploadFileReader = new FileInputStream(f);
int numBytesToRead = 1024;
int availableBytesToRead;
while ((availableBytesToRead = uploadFileReader.available()) > 0)
{
byte[] bufferBytesRead;
bufferBytesRead = availableBytesToRead >= numBytesToRead ? new byte[numBytesToRead]
: new byte[availableBytesToRead];
uploadFileReader.read(bufferBytesRead);
httpOut.write(bufferBytesRead);
httpOut.flush();
}
httpOut.write(("--" + Boundary + "--\r\n").getBytes());
}
httpOut.write(("--" + Boundary + "--\r\n").getBytes());
httpOut.flush();
httpOut.close();
// read & parse the response
InputStream is = theUrlConnection.getInputStream();
StringBuilder response = new StringBuilder();
byte[] respBuffer = new byte[4096];
while (is.read(respBuffer) >= 0)
{
response.append(new String(respBuffer).trim());
}
is.close();
System.out.println(response.toString());
}
public static void main(String[] args) throws Exception
{
List<File> list = new ArrayList<File>();
list.add(new File("C:\\square.png"));
list.add(new File("C:\\narrow.png"));
UploaderExample uploader = new UploaderExample();
uploader.upload(new URL("http://systemout.com/upload.php"), list);
}
}

I'd suggest you take a look at Gallery Remote. This is an open source project for uploading photos to a PHP backend. It's a bit more full featured than what you may need, but you should be able to modify the code to your needs fairly easily.
You could also look at JUpload. It's not as full featured, but it is open source and capable of the task.