File being erased during input output stream
I am trying to send a .txt to an ftp server. The application will send the file but it is empty on the server end AND my original! The file is still there but is 0 kb with all data deleted. I cant seem to figure out what I'm doing wrong. Any ideas?
try{
URL url = new URL("ftp://username:[email protected]/file.txt;type=i");
URLConnection con = url.openConnection();
BufferedInputStream in =
new BufferedInputStream(con.getInputStream());
FileOutputStream out = new FileOutputStream("file.txt");
int i = 0;
byte[] bytesIn = new byte[1024];
while ((i = in.read(bytesIn)) >= 0) {
out.write(bytesIn, 0, i);
out.close();
in.close();
catch(Exception nio){System.out.println(nio);}
I am trying to send a .txt to an ftp server.There's the problem right there. The code you posted copies data FROM the server TO your local system.
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How the buffereing is done in buffered input/output streams?
From the API doc I got to know that they use internal buffer to store bytes before they can be read or written. But i found that File input/output stream also have methods like read(byte[]) or write(byte[]). So what is extra in buffered input/ouput streams? Does the phrase "buffered" suggests that bytes can be read from an array or be written to an array? Am i thinking the right way?How the buffereing is done in buffered input/output
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From the API doc I got to know that they use internal
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Does the phrase "buffered" suggests that bytes can be
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Get multiple Input/Output Stream from same socket ?
For a better express of my problem i will put my test example
I have those 4 classes
package test;
import...
public class ReaderExecutor extends Thread{
private InputStream in = null;
private static int defaultID = 0;
private int ID = getID();
public ReaderExecutor(InputStream in){
this.in = in;
public void run(){
try {
int c ;
while ((c=in.read())!=-1)
System.out.println("ReaderThread " + this.ID + ":" + c);
catch (IOException e) {
System.out.println("ReaderThread "+this.ID+" stopped !");
private static int getID(){
return defaultID++;
package test;
import...
public class WriterExecuter extends Thread{
OutputStream out = null;
private static boolean odd = true;
private boolean isOdd ;
public WriterExecuter(OutputStream out) {
this.out = out;
isOdd = odd;
odd = !odd;
public void run(){
try{
for (int i = isOdd?1:2;i<10;i+=2){
System.err.println(i);
out.write(i);
}catch(Exception e){
System.out.println("WriterThread stopped !");
package test;
import...
public class Main {
public Main() {
public static void main(String[] args) throws Exception {
try{
ServerSocket ss = new ServerSocket(9090);
System.out.println("Ascult ... ");
Socket client = ss.accept();
new ReaderExecutor(client.getInputStream()).start();
//Thread.sleep(2000);
new ReaderExecutor(client.getInputStream()).start();
}catch (Exception e){
e.printStackTrace();
package test;
import...
public class Main1 {
public Main1() {
public static void main(String[] args) {
try{
Socket s = new Socket("localhost",9090);
WriterExecuter t= null ;
t = new WriterExecuter(s.getOutputStream());
t.start();
t = new WriterExecuter(s.getOutputStream());
t.start();
}catch(Exception e){
e.printStackTrace();
}Now if i run successive Main , Main1 i get this output
Ascult ...
ReaderThread 0:0
ReaderThread 1:0
ReaderThread 0:0
ReaderThread 1:0
ReaderThread 0:0
ReaderThread 1:0
ReaderThread 0:0
ReaderThread 1:0
ReaderThread 0:0
ReaderThread 0 stopped !
ReaderThread 1 stopped !The question is can i get other Input/Output individual streams with a separate logic functionality from the same socket?
From this example it seems i can't :(
Thx
AlexFor what you are trying to do the simplest solution is to have one socket per "stream" that is the way they are designed to be used.
However, you can multiplex multiple stream over a single socket, but you have do the coding yourself or use a solution which does this for you e.g. JMS. (There is no support at the socket level for this) -
Questions about input/output streams
In the following tutorial:
http://chortle.ccsu.ctstateu.edu/CS151/Notes/chap85/ch85_10.html
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All my ipod files were erased during an upload
I have never had trouble uploading my ipod until this morning when I was putting several new albums on it, it said they were done uploading so when I clicked on my ipod in iTunes to check if all of them were there, and it hadn't actually done anything. During an upload it said that an artwork file was corrupted. I looked at my iPod and the 'do not disconnect' message was frozen, so I unplugged it and restarted it. When I turned it back on and went to my music, everything was gone instead of the files I just tried to upload. I was using my ipod as a hard drive so none of my files were backed up. I always have had it manually upload songs onto it instead of it automatically copying my library on this computer. I know that my other files are pretty much lost but how did this happen? If it was a specific file how do I locate it and if I don't delete it, will it happen again? I'm so mad right now, I had a 9 hour flight tommorow and I lost over 2000 songs.
Hello Michael,
See this older thread from another forum member Zevoneer discussing the various methods for transferring content from your iPod to your computer.
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B-rock -
Input/output stream coupler (like a pipe, but reversed)
I could write my own class but, for standardization purposes, I was wondering if there is anything in the Java API that does this:
I have a Reader and a Writer and I want to connect them so that as soon as data is available from the Reader, it is written directly to the Writer.
Reader>===>Writer
as opposed to a pipe which looks loke
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Is there such a class?I don't know of such a class, but you have the same API docs available to you as the rest of us. If you don't see it in java.io or java.nio or java.nio(.*), then it's not in the core API. At that point, I'd check sourceforge, jakarta, mindprod. After that, I might be inclined to post here, but I'd probably just say screw it and write my own.
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MultiThreading with Input and Output Streams
Hi,
I have a problem and I think it's because I'm not coding correctly. Please help me if you can understand what I'm doing wrong.
I have a server that spawns a separate thread to go off and collect data from a serial port. It also waits to accept connections from any client and if a connection is made it will send that data to the clients connected.
There is data constantly coming in through the serial port. It is output through a DataOutputStream so when the thread is created in the server, I pipe it into a DataInputStream. I do does because I want the server to then read in the data from the inputstream and then send it out to all my clients.
So far, the way I have it set up seems to do this. But my problem occurs when I try to close a client connection. Instead of removing the socket connection it gives me an error that it can't send data to the client, but it shouldn't be sending data to the client because I just closed it. I realize this is probably because I'm still constantly receiving data from my inputstream and the connection was closed so it can't send that data to the client. I know I need to either close the stream or close my socket but I don't know where this needs to be done. I'm stuck on the correct way to fix this.
My second problem is the initial connection made to receive data from the inputstream. This is probably because I'm not very familiar with how input/output streams work. But instead of just sending the client the current data being received in real time, it'll send all the data that's buffered in the inputstream. I don't want all the data that's been collecting to go to that first client. I only want the recent data that is coming through while the client is connected. Does this make sense? Because after I make a second client connection I don't have this problem because the InputStream is no longer buffered up. Should I be using something else besides the DataInputStream?
I feel like I'm going about this the wrong way. Please advise. I'm shy about showing the code but I've included the bulk of it here in hopes that someone will see what I'm doing wrong. The only part that's left out is the thread that reads from the serial port. I don't seem to have any problems with that thread.
Thanks,
kim
===
import java.io.*;
import java.net.*;
import javax.comm.*;
import java.util.*;
// DataServer waits for a client connection
class DataServer
static final int PORT = 7;
// The ServerSocket to use for accepting new connections
private ServerSocket ss;
// A mapping from sockets to DataOutputStreams. This will
// help us avoid from having to create a DataOutputStream each time
// we want to write to a stream.
private Hashtable outputStreams = new Hashtable();
// The inputstream that will receive serial port data through a
// piped inputstream
public DataInputStream datalogger;
// Constructor and while-accept loop all in one.
public DataServer() throws IOException
try {
// Creating pipe to convert the outputstream from the
// RS232 Thread to an inputstream for the server to read
PipedOutputStream pout = new PipedOutputStream();
PipedInputStream pin = new PipedInputStream(pout);
// The inputstream that will receive data from the RS232Thread
datalogger = new DataInputStream(pin);
// Spawn the thread that will read data through from
// the TINI serial port
new RS232Thread( pout ).start();
// Begin listening for connections and send data
listen();
} catch (IOException ioe) {
System.out.println("Error >> DataServer::DataServer()");
System.out.println(ioe.getMessage());
ioe.printStackTrace();
} finally {
try {
System.out.println( "Closing >> DataServer::DataServer()" );
datalogger.close();
} catch (IOException i ) {
System.out.println( "Error2 >> DataServer::DataServer()" );
System.out.println(i); }
private void listen() throws IOException
// Create the ServerSocket
ss = new ServerSocket( PORT );
// Inform that the server is ready to go
System.out.println( "Listening on " + ss );
// Keep accepting connections forever
while (true) {
// Grab the next incoming connection
Socket s = ss.accept();
// Inform that connection is made
System.out.println( "Connection from " + s );
// Create a DataOutputStream for writing data to the
// other side
DataOutputStream dout = new DataOutputStream( s.getOutputStream() );
// Save this stream so we don't need to make it again
outputStreams.put( s, dout );
// Create a new thread for this connection, and then foret
// about it
new ServerThread( this, s );
// Get an enumeration of all the OutputStreams, one for each client
// connected to the server
Enumeration getOutputStreams() {
return outputStreams.elements();
// Send a message to all clients (utility routine)
void sendToAll( byte[] b ) {
// synchronize on this because another thread might be
// calling removeConnection() and this would screw things up
// while it walks through the list
synchronized( outputStreams ) {
// For each client...
for (Enumeration e = getOutputStreams(); e.hasMoreElements();) {
// ... get the output stream ...
DataOutputStream dout = (DataOutputStream)e.nextElement();
// ... and send the message
try {
dout.write( b );
} catch(IOException ie) {
System.out.println( "Error >> ServerThread::sendToAll()" );
System.out.println( ie );
// remove a socket, and it's corresponding output stream, from the
// list. This is usually called by a connection thread that has
// discovered that the connection to the client is dead.
void removeConnection( Socket s ) {
// Synchronize so it doesn't mess up sendToAll() while it walks
// down the list of all output streams
synchronized( outputStreams ) {
// Inform about removal
System.out.println( "Removing connection to " + s );
// Remove if from our hastable/list
outputStreams.remove( s );
// Make sure it's closed
try {
s.close();
} catch( IOException ie ) {
System.out.println( "Error closing " + s );
ie.printStackTrace();
// main - Opens a server socket and spins off a new thread each time
// a new client connection is accepted on this socket.
public static void main(String[] args) throws Exception
System.out.println("Starting DataServer version 1.0 ...");
try
new DataServer();
catch (IOException ioe)
System.out.println( "Error >> DataServer::main()" );
System.out.println(ioe.getMessage());
ioe.printStackTrace();
class ServerThread extends Thread
//The Server that spawned this thread
private DataServer server;
// The Socket connected to the client
private Socket socket;
//Constructor
public ServerThread( DataServer server, Socket socket )
// save the parameters
this.server = server;
this.socket = socket;
// Start up the thread
start();
// This runs in a separate thread when start() is called in the
// constructor
public void run() {
try {
// The inputstream receiving data from the global inputstream
// that is piped to the RS232 Thread
// ???? is this where i'm messing up ???
DataInputStream in = new DataInputStream( server.datalogger );
int num = 0;
byte[] d = new byte[1];
// read from the inputstream over and over, forever ...
while( ( num = in.read(d) ) > 0 ) {
// ... and have the server send it to all clients
server.sendToAll( d );
} catch (IOException ioe) {
System.out.println( "Error >> ServerThread::run()" );
System.out.println(ioe.getMessage());
ioe.printStackTrace();
} finally {
// The connection is closed for one reason or another,
// so have the server dealing with it
System.out.println( "Closing" );
server.removeConnection( socket );A couple of things to note...
First, you are looping infinitely in your server's constructor. Since the constructor is never completing, your server object is never completely constructed - this may cause indeterminate behaviour when you pass a reference to the server to another thread.
Second, I would recommend fixing your issues by modifying your design somewhat. The design I would recommend (read: The design I would use) is:
A server object, with a public listen method. The constructor spawns a thread to constantly read from the serial port and forward the data read back to the server, via a multicast (sendToAll) method.
The listen method sets up a server socket to accept connections, and in a loop opens client sockets and stores them in a set.
The multicast method iterates through the list of open client sockets, and for each in turn confirms that it is still open. If open, send the data down the socket's output stream; if closed, remove the socket from the set.
Note that this design includes only two threads - the main thread listens for and accepts new socket connections, while the extra thread collects data from the serial port, multicasts it to all of the open sockets, and removes all of the closed sockets. If you require to perform any other communication with the sockets, it may be necessary to create a thread for those sockets, to facilitate reading from their input streams, but in the given design, this is not necessary.
I hope this helps,
-Troy -
Using two ports or Using two Input / Outputs
I'm explaining my project. It s almost done. I send message and data to server and it is stored in server. From the begining I'm using
BufferedReader - PrintWriterAnd I cannot send files because they are binary. I have to use
BufferedInputStream - BufferedOutputStreamI cannot change my input / output. So I found two solutions:
1) Connecting from another port with another socket. -> Using this it blames the ports. I cannot transfer anything from my first port.
2) Using another input / output streams from the same port. -> I didn't tried it . Does anyone tried this. Is it possible to do this.
That's the end of my project. I will give the name of project who gives me a good answer :D
Best Regards, Bulent.I cannot change my input / output. Why not?
So I found two solutions:
1) Connecting from another port with another
er socket. -> Using this it blames the ports. I
cannot transfer anything from my first port.Huh? Unless the server stops you, there is nothing in sockets that prevents you, as a client, from connecting to the server twice.
2) Using another input / output streams from the
he same port. -> I didn't tried it . Does anyone
tried this. Is it possible to do this. Nothing stops you from using an InputStream to create two different buffered solutions.
I wouldn't even attempt this myself. It would create a very fragile application. But you could try it. You would need to carefully control when the two connections were used and in particular when they were closed. You could do this by wrapping both in a class. -
Oracle BLOB Writes the Bytes Twice to Output Stream
Hi,
I have a very strange problem when working with oracle.sql.BLOB; I cannot figure out what it's causing my BLOB stream output to double the amount of data inserted into the Oracle database. I have a table that contains two BLOB objects(image files) and the goal is to insert two images into each row by BLOB stream.
For example, if the image_bin size is 800k and image_thumbnail size is 100k, this code actually writes 1600k (double) and 200k (double) the amount of bytes to each BLOB column, respectively. The print method in insertBlob() indicates a correct number of bytes being written to the output stream (800k and 100k).
I know for the fact the retrieval method (not mentioned here) doesn't duplicate the bytes when it's read because I have written another test program that does not utilize oracle.sql.BLOB but instead uses PreparedStatement's setBinaryStream(index, InputStream, size_of_file) and it accurately writes the exact image size (no double sizing) to the database -- but not with BLOB. Here's a snippet of my code, note that the actual writing occurs in insertBlob():
private void insertBlob(java.sql.Blob lobImage, String imgName)
throws SQLException, IOException {
File imgFile = null;
FileInputStream imgOnDisk = null;
OutputStream imgToDB = null;
int bufferSize = 0;
oracle.sql.BLOB blobImage = (oracle.sql.BLOB) lobImage;
try {
int bytesRead = 0;
long bytesWritten = 0L;
byte[] byteBuffer = null;
bufferSize = blobImage.getBufferSize();
byteBuffer = new byte[bufferSize];
imgFile = new File(imgName);
// Stream to read the file from the local disk
imgOnDisk = new FileInputStream(imgFile);
// Stream to write to the Oracle database
imgToDB = blobImage.setBinaryStream(imgFile.length());
// Read from the disk file and write to the database
while ((bytesRead = imgOnDisk.read(byteBuffer)) != -1 ) {
imgToDB.write(byteBuffer, 0, bytesRead);
bytesWritten += bytesRead;
} // end of while
System.out.print("Done. " + bytesWritten + "-bytes inserted, buffer size: " +
bufferSize + "-bytes, chunk size: " +
blobImage.getChunkSize() + ".\n");
} catch (SQLException sqlEx) {
System.out.println("SQLException caught: JDBCOracleLOBBinaryStream.processBlob()");
connRollback();
throw sqlEx;
} catch (IOException ioe) {
System.out.println("IOException caught: JDBCOracleLOBBinaryStream.processBlob()");
throw ioe;
} finally {
try {
if (imgOnDisk != null ) {
imgOnDisk.close();
if (imgToDB != null ) {
imgToDB.close();
} catch (IOException ioeClosing) {
System.out.println("IOException caught: JDBCOracleLOBBinaryStream.processBlob() " +
"on closing stream.");
ioeClosing.printStackTrace();
} // end of finally
public void insertImageIntoOracleDB() throws SQLException, IOException {
PreparedStatement pstmt = null;
Statement stmt = null;
ResultSet rset = null;
try {
this.getConnection(_driver, host, port, database, user, _pass);
pstmt = conn.prepareStatement("INSERT INTO " +
" gallery_v (picture_id, picture_title, image_bin, image_thumbnail) " +
" VALUES (?, ?, EMPTY_BLOB(), EMPTY_BLOB())");
pstmt.setInt(1, picID);
pstmt.setString(2, picTitle);
pstmt.executeUpdate();
stmt = conn.createStatement();
rset = stmt.executeQuery("SELECT image_bin, image_thumbnail FROM gallery_v " +
" WHERE picture_id = " + picID + " FOR UPDATE");
int rsetCount = 0;
oracle.sql.BLOB imgBlob = null;
oracle.sql.BLOB imgThumbBlob = null;
while (rset.next()) {
imgBlob = ((OracleResultSet) rset).getBLOB("image_bin");
System.out.print("Inserting " + img + "... ");
insertBlob(imgBlob, img);
imgThumbBlob = ((OracleResultSet) rset).getBLOB("image_thumbnail");
System.out.print("Inserting " + imgThumb + "... ");
insertBlob(imgThumbBlob, imgThumb);
rsetCount++;
System.out.println("\nNumber of rows updated: " + rsetCount);
conn.commit();
} catch (SQLException sqlEx) {
System.out.println("SQLException caught: JDBCOracleLOBBinaryStream.insertImageIntoOracleDB()");
connRollback();
throw sqlEx;
} catch (IOException ioe) {
throw ioe;
} finally {
try {
if (rset != null) {
rset.close();
if (pstmt != null) {
pstmt.close();
if (stmt != null) {
stmt.close();
closeConnection();
} catch (SQLException closingSqlEx) {
System.out.println("SQLException caught: JDBCOracleLOBBinaryStream.insertImageIntoOracleDB() " +
"on closing ResultSet or PreparedStatement.");
closingSqlEx.printStackTrace();
} // end of finally
}Make a lumpy mistake; the new BLOB#setBinaryStream() method takes a position of where the data is read from in the stream given to it. So the following code:
imgToDB = blobImage.setBinaryStream(imgFile.length());
Starts off from the end of the file. Now I don't understand how this position would result in the duplicated amount of bytes read from the binary file (an image here) to the output stream! The correct line should be:
imgToDB = blobImage.setBinaryStream(0L);
ARGH!!! Now everything works as it expected. I gotta read the API's more carefully as I was expecting the same semantic parameter as PreparedStatement#setBinaryStream() which takes the length of the stream as one of its parameters.
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