Develop Reference

Display or download image through the browser

I have a server that displays what the user asks for from the browser, I am using linux and when i run the server and ask for a file like Image.png using this link localhost:9999/Image.png on FireFox i get this message:
The image "localhost:9999/Image.png" cannot be displayed because it
contains errors.
But when i change the variable fileName to an HTML file it works perfectly and i can visualize the html page.
What am I doing wrong??
This is my server:
import java.io.*;
import java.net.*;
import java.util.Scanner;
public class Server {
public static void main(String args[]) throws IOException {
// Declarem les variables a utilitzar
ServerSocket serverSocket = null;
Socket socket = null;
InputStream inS = null;
OutputStream outS = null;
try
{
serverSocket = new ServerSocket(9999);
while(true)
{
socket= serverSocket.accept();
inS = socket.getInputStream();
outS = socket.getOutputStream();
try{
BufferedReader br = new BufferedReader(new InputStreamReader(inS));
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(outS));
System.out.println("THis is what the user wants = " + br.readLine());
String fileName = "Image.png";
String extension= "";
int i = fileName.lastIndexOf('.');
if (i > 0) {
extension = fileName.substring(i+1);
}
String dataReturn = "";
if(extension.equals("png"))
{
bw.write("HTTP/1.0 200 OK\r\n");
bw.write("Content-Type: image/png\r\n");
bw.write("\r\n");
FileReader myFilepng = new FileReader(fileName);
Scanner scanner1 = new Scanner(myFilepng);
dataReturn = "";
while(scanner1.hasNextLine()) {
dataReturn = scanner1.nextLine();
System.out.println(dataReturn);
bw.write(dataReturn);
}
scanner1.close();
}else{
if(extension.equals("html"))
{
bw.write("HTTP/1.0 200 OK\r\n");
bw.write("Content-Type: text/html\r\n");
bw.write("\r\n");
bw.write("<TITLE>"+fileName+"/TITLE>");
FileReader myFile = new FileReader(fileName);
Scanner scanner = new Scanner(myFile);
dataReturn = "";
while(scanner.hasNextLine()) {
dataReturn = scanner.nextLine();
System.out.println(dataReturn);
bw.write(dataReturn);
}
scanner.close();
}
}
bw.close();
}catch(Exception e)
{
}
}
}catch (IOException e) {
System.out.println(e);
}
inS.close();
outS.close();
socket.close();
}
}

You are not writing the contents of your png file to your bw BufferedWriter. Instead you are only sending the header of the response to the client. As you are indicating your response is a png image and there is no data, your browser is telling you the image contains errors (in fact, it does not contains nothing at all).
Open the png filename, write the data to your "bw" buffer to send it to the client. That should be enough.
Edit:
To to that, try the following code for your "if" is image:
if(extension.equals("png"))
{
File file = new File(fileName);
FileInputStream fis = new FileInputStream(file);
byte[] data = new byte[(int) file.length()];
fis.read(data);
fis.close();
DataOutputStream binaryOut = new DataOutputStream(outS);
binaryOut.writeBytes("HTTP/1.0 200 OK\r\n");
binaryOut.writeBytes("Content-Type: image/png\r\n");
binaryOut.writeBytes("Content-Length: " + data.length);
binaryOut.writeBytes("\r\n\r\n");
binaryOut.write(data);
binaryOut.close();
}
Note the use of a binary stream in comparison to the text stream you use in case of html.

How to transfer a file from REST php server to a Java client

I've been surfing over this site looking for an example or "light at the end of the tunnel" about how to write a code that let me download a file from a REST server in PHP to a client in JAVA.
The client will make a GET request with an ID of the file, and then the PHP REST code should response with the file, and JAVA receive that file and store it in the Hard Drive.
Any idea...?
I tried to do the PHP Rest server like this...:
$file = 'path_to_file/file.mp3';
$content = readfile($file);
And this $content var, is sent as the response...
The client... I wrote is:
try {
URL url = new URL("url/to/rest/server");
HttpURLConnection conn (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setRequestProperty("Accept", "Content-Disposition: filename\"music.mp3\"");
if(conn.getResponseCode() != 200) {
throw new RuntimeException("Failed : HTTP error code: " + conn.getResponseCode());
}
BufferedReader br = new BufferedReader(new InputStreamReader((conn.getInputStream())));
try {
String output;
File newFile = newFile("/some/path/file.mp3");
fileWriter fw = new FileWriter(newFile);
while ((output = br.readLine()) != null) {
fw.write(output);
}
fw.close();
} catch (IOException iox) {
//do
}
} catch (MalformedURLException e) {
//do
}
The problem with my examples is that when I receive the file on the client is kind of corrupted or something!... in my example with an mp3 file, any music player on the client says that file is corrupted or it doesn't work.
Thanks for any help.

When dealing with binary data (MP3 files) you should use InputStream and OutputStream and not Readers/Writers. Additionally, the BufferedReader.readLine() strips any 'newlines' from the output too.
Because you are using Readers/Writers, the binary data is being converted to Strings, and I am sure there's a lot of corruption happening.
Try the following:
InputStream is = conn.getInputStream();
byte[] buffer = new byte[10240]; // 10K is a 'reasonable' amount
try {
File newFile = newFile("/some/path/file.mp3");
FileOutputStream fos = new FileOutputStream(newFile);
int len = 0;
while ((len = is.read(buffer)) >= 0) {
fos.write(buffer, 0, len);
}
fos.close();
} catch (IOException iox) {
//do
}

Java UTF-8 encoding not set to URLConnection

I'm trying to retrieve data from http://api.freebase.com/api/trans/raw/m/0h47
As you can see in text there are sings like this: /ælˈdʒɪəriə/.
When I try to get source from the page I get text with sings like ú etc.
So far I've tried with the following code:
urlConnection.setRequestProperty("Accept-Charset", "UTF-8");
urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded;charset=utf-8");
What am I doing wrong?
My entire code:
URL url = null;
URLConnection urlConn = null;
DataInputStream input = null;
try {
url = new URL("http://api.freebase.com/api/trans/raw/m/0h47");
} catch (MalformedURLException e) {e.printStackTrace();}
try {
urlConn = url.openConnection();
} catch (IOException e) { e.printStackTrace(); }
urlConn.setRequestProperty("Accept-Charset", "UTF-8");
urlConn.setRequestProperty("Content-Type", "text/plain; charset=utf-8");
urlConn.setDoInput(true);
urlConn.setUseCaches(false);
StringBuffer strBseznam = new StringBuffer();
if (strBseznam.length() > 0)
strBseznam.deleteCharAt(strBseznam.length() - 1);
try {
input = new DataInputStream(urlConn.getInputStream());
} catch (IOException e) { e.printStackTrace(); }
String str = "";
StringBuffer strB = new StringBuffer();
strB.setLength(0);
try {
while (null != ((str = input.readLine())))
{
strB.append(str);
}
input.close();
} catch (IOException e) { e.printStackTrace(); }

The HTML page is in UTF-8, and could use arabic characters and such. But those characters above Unicode 127 are still encoded as numeric entities like ú. An Accept-Encoding will not, help, and loading as UTF-8 is entirely right.
You have to decode the entities yourself. Something like:
String decodeNumericEntities(String s) {
StringBuffer sb = new StringBuffer();
Matcher m = Pattern.compile("\\&#(\\d+);").matcher(s);
while (m.find()) {
int uc = Integer.parseInt(m.group(1));
m.appendReplacement(sb, "");
sb.appendCodepoint(uc);
}
m.appendTail(sb);
return sb.toString();
}
By the way those entities could stem from processed HTML forms, so on the editing side of the web app.
After code in question:
I have replaced DataInputStream with a (Buffered)Reader for text. InputStreams read binary data, bytes; Readers text, Strings. An InputStreamReader has as parameter an InputStream and an encoding, and returns a Reader.
try {
BufferedReader input = new BufferedReader(
new InputStreamReader(urlConn.getInputStream(), "UTF-8"));
StringBuilder strB = new StringBuilder();
String str;
while (null != (str = input.readLine())) {
strB.append(str).append("\r\n");
}
input.close();
} catch (IOException e) {
e.printStackTrace();
}

Try adding also the user agent to your URLConnection:
urlConnection.setRequestProperty("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.155 Safari/537.36");
This solved my decoding problem like a charm.

Well I'm thinking the problem is when you are reading from the stream. You should either call the readUTF method on the DataInputStream instead of calling readLine or, what I would do, would be to create an InputStreamReader and set the encoding, then you can read from the BufferedReader line by line (this would be inside your existing try/catch):
Charset charset = Charset.forName("UTF8");
InputStreamReader stream = new InputStreamReader(urlConn.getInputStream(), charset);
BufferedReader reader = new BufferedReader(stream);
StringBuffer responseBuffer = new StringBuffer();
String read = "";
while ((read = reader.readLine()) != null) {
responseBuffer.append(read);
}

Android App Internal Data Storage

I am attempting to save an array of longs as a text file using the Android's internal memory, and then access that array in a different activity. After noticing that was broken, I isolated the problem in this chunk of code below.
long[] timings = {200, 400, 600, 1400};
try {
FileOutputStream fos = openFileOutput("timings", Context.MODE_PRIVATE);
OutputStreamWriter osw = new OutputStreamWriter(fos);
osw.write(Arrays.toString(timings));
osw.close();
FileInputStream fis = openFileInput("timings");
InputStreamReader isReader = new InputStreamReader(fis);
char[] buffer = new char[timings.length];
isReader.read(buffer);
textField.setText(Arrays.toString(buffer));
fis.close();
} catch (IOException e1) {
e1.printStackTrace();
}
The text field that is set to display what is read from the file has the following result:
[[,2,0,0]
The result I expected was the original array from above. What am I doing wrong here? Any help or advice would be appreciated.

Replace this :
InputStreamReader isReader = new InputStreamReader(fis);
char[] buffer = new char[timings.length];
isReader.read(buffer);
textField.setText(Arrays.toString(buffer));
with this :
DataInputStream in = new DataInputStream(fis);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String sTemp1 = "", sTemp2 = "";
while ((sTemp1 = br.readLine()) != null) {
sTemp2 = sTemp1;
}
in.close();
textField.setText(sTemp2);
I hope it will help you.

Socket Programming file upload issues?Complete file not uploading

Hi i am using the following code for uploding my file from android phone to the server bt the file does not upload completely..e.g i uploded a 11kb file and got only 8kb file at the server.What am i doing wrong?
Client side
Socket skt = new Socket"112.***.*.**", 3000);
String FileName=fil.getName();
PrintWriter out2 = new PrintWriter(new BufferedWriter(new OutputStreamWriter(skt.getOutputStream())),true);
out2.println("Upload");
out2.println(FileName);
out2.println(spinindx);
out2.println(singleton.arrylst_setngs.get(0).toString());
out2.println(singleton.arrylst_setngs.get(1).toString());
out2.println(singleton.arrylst_setngs.get(2).toString());
out2.println(singleton.arrylst_setngs.get(3).toString());
out2.println(singleton.arrylst_setngs.get(4).toString());
out2.flush();
//Create a file input stream and a buffered input stream.
FileInputStream fis = new FileInputStream(fil);
BufferedInputStream in = new BufferedInputStream(fis);
BufferedOutputStream out = new BufferedOutputStream(skt.getOutputStream());
//Write the file to the server socket
int i;
byte[] buf = new byte[512];
while ((i = in.read(buf)) != -1) {
out.write(buf,0,i);
publishProgress(in.available());
System.out.println(i);
}
//Close the writers,readers and the socket.
in.close();
out.flush();
out.close();
out2.close();
skt.close();
}
catch( Exception e ) {
System.out.println(e);
}
The server side
InputStream inStream = socket.getInputStream();
BufferedReader inm = new BufferedReader(new InputStreamReader(inStream));
String Request=inm.readLine();
if(Request.equals("Upload")){
fileName = inm.readLine();
chosn = inm.readLine();
lt=inm.readLine();
cs = inm.readLine();
om = inm.readLine();
o = inm.readLine();
check=inm.readLine();
//Read, and write the file to the socket
BufferedInputStream in = new BufferedInputStream(inStream);
int i=0;
File f=new File("D:/data/"+filePrefx+fileName);
if(!f.exists()){
f.createNewFile();
}
FileOutputStream fos = new FileOutputStream("D:/data/"+filePrefx+fileName);
BufferedOutputStream out = new BufferedOutputStream(fos);
byte[] buf = new byte[512];
while ((i = in.read(buf)) != -1) {
System.out.println(i);
out.write(buf,0,i);
System.out.println("Receiving data...");
}
in.close();
inStream.close();
out.close();
fos.close();
socket.close();

Looks like you are using both a BufferedReader and a BufferedInputStream on the same underlying socket at the server side, and two kinds of output stream/writer at the client. So your BufferedReader is buffering, which is what it's supposed to do, and thus 'stealing' some of the data you're expecting to read with the BufferedInputStream. Moral: you can't do that. Use DataInputStream & DataOutputStream only, and writeUTF()/readUTF() for the 8 lines you are reading from the client before the file.

You shared the same underlying InputStream between your BufferedReader and bufferedInputStream.
What happened is, when you do the reading through BufferedReader, it reads more than the a few lines you requested from the underlying InputStream into its own internal buffer. And when you create the BufferedInputStream, the data has already been read by the BufferedReader. So Apart from what EJP suggested not to use any buffered class, you can create the BufferedInputStream, and then create the Reader on Top of it. The code is something like this:
BufferedInputStream in = new BufferedInputStream(inStream);
Reader inm = new InputStreamReader(in);
Add it to the beginning of your server code and remove this line:
BufferedInputStream in = new BufferedInputStream(inStream);

See this, i never tried though
void read() throws IOException {
log("Reading from file.");
StringBuilder text = new StringBuilder();
String NL = System.getProperty("line.separator");
Scanner scanner = new Scanner(new FileInputStream(fFileName), fEncoding);
try {
while (scanner.hasNextLine()){
text.append(scanner.nextLine() + NL);
}
}
finally{
scanner.close();
}
log("Text read in: " + text);
}
Shamelessly copied from
http://www.javapractices.com/topic/TopicAction.do?Id=42