String.getBytes() & String(byte[]) - java.nio.BufferOverflowException

The application in question uses JNI for legacy integration and I suspect the legacy code is corrupting the stack causing the above error. However, the error does not occur in Java 1.3, only Java 1.4.
Is there some way to suppress 1.4's use of the native IO API when encoding and decoding byte streams? This would at least provide a workaround in the meantime.
Thanks.

This is beginning to make a little sense. The problem is that you got a String and you don't want one. A String wraps an array of chars, which your app needs, right? Specifically they're chars because you need 16-bit char sets.
Presumably the getBytes() method call is used to get an array of bytes for some data transfer operation. java.nio was probably added in 1.4 as it has some very efficient ways of handling buffers as simultaneously of two or more types. It's trying to use the underlying char array as a byte array and there's a straight up bug someplace.
Workaround is strange to contemplate, but I'm pretty sure it will work: use String.getChars() to get an array of chars, and then use java.nio yourself to create your byte array! If you've never been there, it's not very hard. I use nio all the time and it's never been a problem.

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    Hi!
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    Is there any alternative to solve this problem.I am getting the error
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Vijendra                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

  • Javac compiler throws java.nio.BufferOverflowException!!Why?

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              // Start a new connection
              SocketChannel socket = this.initiateConnection();
              // Register the response handler
              this.rspHandlers.put(socket, handler);
              // And queue the data we want written
              synchronized (this.pendingData) {
                   List queue = (List) this.pendingData.get(socket);
                   if (queue == null) {
                        queue = new ArrayList();
                        this.pendingData.put(socket, queue);
                   queue.add(ByteBuffer.wrap(data));
              // Finally, wake up our selecting thread so it can make the required changes
              this.selector.wakeup();
              handler.waitForResponse();
         public void run() {
              while (true) {
                   try {
                        // Process any pending changes
                        synchronized (this.pendingChanges) {
                             Iterator changes = this.pendingChanges.iterator();
                             while (changes.hasNext()) {
                                  ChangeRequest change = (ChangeRequest) changes.next();
                                  switch (change.type) {
                                  case ChangeRequest.CHANGEOPS:
                                       SelectionKey key = change.socket.keyFor(this.selector);
                                       key.interestOps(change.ops);
                                       break;
                                  case ChangeRequest.REGISTER:
                                       change.socket.register(this.selector, change.ops);
                                       break;
                             this.pendingChanges.clear();
                        // Wait for an event one of the registered channels
                        this.selector.select();
                        // Iterate over the set of keys for which events are available
                        Iterator selectedKeys = this.selector.selectedKeys().iterator();
                        while (selectedKeys.hasNext()) {
                             SelectionKey key = (SelectionKey) selectedKeys.next();
                             selectedKeys.remove();
                             if (!key.isValid()) {
                                  continue;
                             // Check what event is available and deal with it
                             if (key.isConnectable()) {
                                  this.finishConnection(key);
                             } else if (key.isReadable()) {
                                  this.read(key);
                             } else if (key.isWritable()) {
                                  this.write(key);
                   } catch (Exception e) {
                        e.printStackTrace();
         private void read(SelectionKey key) throws IOException {
              SocketChannel socketChannel = (SocketChannel) key.channel();
              // Clear out our read buffer so it's ready for new data
              this.readBuffer.clear();
              // Attempt to read off the channel
              int numRead;
              try {
                   numRead = socketChannel.read(this.readBuffer);
              } catch (IOException e) {
                   // The remote forcibly closed the connection, cancel
                   // the selection key and close the channel.
                   key.cancel();
                   socketChannel.close();
                   return;
              System.out.println("READ");
              if (numRead == -1) {
                   // Remote entity shut the socket down cleanly. Do the
                   // same from our end and cancel the channel.
                   key.channel().close();
                   key.cancel();
                   return;
              // Handle the response
              this.handleResponse(socketChannel, this.readBuffer.array(), numRead);
         private void handleResponse(SocketChannel socketChannel, byte[] data, int numRead) throws IOException {
              // Make a correctly sized copy of the data before handing it
              // to the client
              byte[] rspData = new byte[numRead];
              System.arraycopy(data, 0, rspData, 0, numRead);
              // Look up the handler for this channel
              RspHandler handler = (RspHandler) this.rspHandlers.get(socketChannel);
              // And pass the response to it
              if (handler.handleResponse(rspData)) {
                   // The handler has seen enough, close the connection
                   socketChannel.close();
                   socketChannel.keyFor(this.selector).cancel();
         private void write(SelectionKey key) throws IOException {
              SocketChannel socketChannel = (SocketChannel) key.channel();
              synchronized (this.pendingData) {
                   List queue = (List) this.pendingData.get(socketChannel);
                   // Write until there's not more data ...
                   while (!queue.isEmpty()) {
                        ByteBuffer buf = (ByteBuffer) queue.get(0);
                        socketChannel.write(buf);
                        if (buf.remaining() > 0) {
                             // ... or the socket's buffer fills up
                             break;
                        queue.remove(0);
                   if (queue.isEmpty()) {
                        // We wrote away all data, so we're no longer interested
                        // in writing on this socket. Switch back to waiting for
                        // data.
                        key.interestOps(SelectionKey.OP_READ);
         private void finishConnection(SelectionKey key) throws IOException {
              SocketChannel socketChannel = (SocketChannel) key.channel();
              // Finish the connection. If the connection operation failed
              // this will raise an IOException.
              try {
                   socketChannel.finishConnect();
              } catch (IOException e) {
                   // Cancel the channel's registration with our selector
                   System.out.println(e);
                   key.cancel();
                   return;
              // Register an interest in writing on this channel
              key.interestOps(SelectionKey.OP_WRITE);
         private SocketChannel initiateConnection() throws IOException {
              // Create a non-blocking socket channel
              SocketChannel socketChannel = SocketChannel.open();
              socketChannel.configureBlocking(false);
              // Kick off connection establishment
              socketChannel.connect(new InetSocketAddress(this.host, this.port));
              // Queue a channel registration since the caller is not the
              // selecting thread. As part of the registration we'll register
              // an interest in connection events. These are raised when a channel
              // is ready to complete connection establishment.
              synchronized(this.pendingChanges) {
                   this.pendingChanges.add(new ChangeRequest(socketChannel, ChangeRequest.REGISTER, SelectionKey.OP_CONNECT));
              return socketChannel;
         private Selector initSelector() throws IOException {
              // Create a new selector
              return SelectorProvider.provider().openSelector();
    public class RspHandler {
         private byte[] rsp = null;
         public synchronized boolean handleResponse(byte[] rsp) {
              this.rsp = rsp;
              this.notify();
              return true;
         public synchronized void waitForResponse() {
              while(this.rsp == null) {
                   try {
                        this.wait();
                   } catch (InterruptedException e) {
              System.out.println(new String(this.rsp));
    }          NioClient NioClient = new NioClient();
              Thread t = new Thread(NioClient);
              t.setDaemon(true);
              t.start();
              RspHandler handler = new RspHandler();          
              NioClient.connect("69.28.156.250", 27040, handler);
              NioClient.connect("72.165.61.188", 27040, handler);
              NioClient.connect("208.111.133.84", 27011, handler);
              NioClient.connect("72.165.61.136", 27012, handler);
    Edited by: 915967 on 01.08.2012 7:07

  • Java.nio select() method return 0 in my client application

    Hello,
    I'm developing a simple chat application who echo messages
    But my client application loop because the select() method return 0
    This is my code
    // SERVER
    package test;
    import java.io.IOException;
    import java.net.InetSocketAddress;
    import java.nio.channels.SelectionKey;
    import java.nio.channels.Selector;
    import java.nio.channels.ServerSocketChannel;
    import java.nio.channels.SocketChannel;
    import java.util.Iterator;
    import java.util.Set;
    public class Server {
         private int port = 5001;
         public void work() {               
              try {
                   ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
                   serverSocketChannel.configureBlocking(false);
                   InetSocketAddress isa = new InetSocketAddress(port);               
                   serverSocketChannel.socket().bind(isa);
                   Selector selector = Selector.open();
                   serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
                   System.out.println("Listing on "+port);
                   while(selector.select()>0) {
                        Set keys = selector.selectedKeys();
                        for(Iterator i = keys.iterator(); i.hasNext();) {
                             SelectionKey key = (SelectionKey) i.next();
                             i.remove();
                             if (key.isAcceptable()) {
                                  ServerSocketChannel keyChannel = (ServerSocketChannel)key.channel();                              
                                  SocketChannel channel = keyChannel.accept();
                                  channel.configureBlocking(false);                              
                                  channel.register(selector, SelectionKey.OP_READ );
                             } else if (key.isReadable()) {
                                  SocketChannel keyChannel = (SocketChannel) key.channel();
                                  String m = Help.read(keyChannel );
                                  Help.write(m.toUpperCase(), keyChannel );
              } catch (IOException e) {                                             
                   e.printStackTrace();                         
         public static void main(String[] args) {
              Server s = new Server();
              s.work();
    // CLIENT
    package test;
    import java.awt.event.KeyAdapter;
    import java.awt.event.KeyEvent;
    import java.awt.event.WindowAdapter;
    import java.awt.event.WindowEvent;
    import java.io.IOException;
    import java.net.InetSocketAddress;
    import java.nio.channels.SelectionKey;
    import java.nio.channels.Selector;
    import java.nio.channels.SocketChannel;
    import java.util.Iterator;
    import java.util.Set;
    import javax.swing.JFrame;
    import javax.swing.JScrollPane;
    import javax.swing.JTextArea;
    import javax.swing.JTextField;
    import javax.swing.SwingUtilities;
    public class Client extends JFrame  {
         private String host = "localhost";
         private int port = 5001;
         private SocketChannel socketChannel;
         private Selector selector;
         public void work() {               
              try {
                   socketChannel = SocketChannel.open();
                   socketChannel.configureBlocking(false);
                   InetSocketAddress isa = new InetSocketAddress(host, port);               
                   socketChannel.connect(isa);
                   selector = Selector.open();
                   socketChannel.register(selector, SelectionKey.OP_CONNECT | SelectionKey.OP_READ );
                   while(true) {
                        selector.select();
                        Set keys = selector.selectedKeys();
                        for(Iterator i = keys.iterator(); i.hasNext();) {
                             SelectionKey key = (SelectionKey) i.next();
                             i.remove();
                             if (key.isConnectable()) {
                                  SocketChannel keyChannel = (SocketChannel) key.channel();
                                  if (keyChannel.isConnectionPending()) {
                                       System.out.println("Connected "+keyChannel.finishConnect());                                                                           
                             } else if (key.isReadable()) {                                                                                                                                                           
                                  SocketChannel keyChannel = (SocketChannel) key.channel();                                             
                                  String m = Help.read(keyChannel);
                                  display(m);                                                                                                                                                                                                                   
              } catch (IOException e) {                                             
                   e.printStackTrace();                         
         private void display(final String m) {
              SwingUtilities.invokeLater(new Runnable() {
                   public void run() {
                        area.append(m+"\n");
                        textFieed.setText("");
         private void sendMessage(final String m) {
              Thread t = new Thread(new Runnable() {               
                   public void run() {                                                                                
                        try {                         
                             Help.write(m, socketChannel);
                        } catch (IOException e) {               
                             e.printStackTrace();
              t.start();                    
         public Client() {
              addWindowListener(new WindowAdapter() {
                   public void windowClosing(WindowEvent e) {
                        System.exit(1);
              textFieed.addKeyListener(new KeyAdapter() {
                   public void keyPressed(KeyEvent e) {
                        if (e.getKeyCode()== KeyEvent.VK_ENTER) {
                             String m = textFieed.getText();
                             sendMessage(m);     
              area.setEditable(false);
              getContentPane().add(textFieed, "North");
              getContentPane().add(new JScrollPane(area));
              setBounds(200, 200, 400, 300);
              show();
         private String messageToSend;
         private JTextArea area = new JTextArea();
         JTextField textFieed = new JTextField();
         public static void main(String[] args) {
              Client s = new Client();
              s.work();
    // HELPER CLASS
    package test;
    import java.io.IOException;
    import java.nio.ByteBuffer;
    import java.nio.CharBuffer;
    import java.nio.channels.SocketChannel;
    import java.nio.charset.Charset;
    import java.nio.charset.CharsetDecoder;
    import java.nio.charset.CharsetEncoder;
    public class Help {
         private static Charset charset = Charset.forName("us-ascii");
         private static CharsetEncoder enc = charset.newEncoder();
         private static CharsetDecoder dec = charset.newDecoder();
         private static void log(String m) {
              System.out.println(m);
         public static String read(SocketChannel channel) throws IOException {
              log("*** start READ");                              
              int n;
              ByteBuffer buffer = ByteBuffer.allocate(1024);
              while((n = channel.read(buffer)) > 0) {
                   System.out.println("     adding "+n+" bytes");
              log("  BUFFER REMPLI : "+buffer);
              buffer.flip();               
              CharBuffer cb = dec.decode(buffer);          
              log("  CHARBUFFER : "+cb);
              String m = cb.toString();
              log("  MESSAGE : "+m);          
              log("*** end READ");
              //buffer.clear();
              return m;                    
         public static void write(String m, SocketChannel channel) throws IOException {          
              log("xxx start WRITE");          
              CharBuffer cb = CharBuffer.wrap(m);
              log("  CHARBUFFER : "+cb);          
              ByteBuffer  buffer = enc.encode(cb);
              log("  BUFFER ALLOUE REMPLI : "+buffer);
              int n;
              while(buffer.hasRemaining()) {
                   n = channel.write(buffer);                         
              System.out.println("  REMAINING : "+buffer.hasRemaining());
              log("xxx end WRITE");

    Here's the fix for that old problem. Change the work method to do the following
    - don't register interest in things that can't happen
    - when you connect register based on whether the connection is complete or pending.
    - add the OP_READ interest once the connection is complete.
    This doesn't fix all the other problems this code will have,
    eg.
    - what happens if a write is incomplete?
    - why does my code loop if I add OP_WRITE interest?
    - why does my interestOps or register method block?
    For code that answers all those questions see my obese post Taming the NIO Circus
    Here's the fixed up Client code
    // CLIENT
    package test
    import java.awt.event.KeyAdapter;
    import java.awt.event.KeyEvent;
    import java.awt.event.WindowAdapter;
    import java.awt.event.WindowEvent;
    import java.io.IOException;
    import java.net.InetSocketAddress;
    import java.nio.channels.SelectionKey;
    import java.nio.channels.Selector;
    import java.nio.channels.SocketChannel;
    import java.util.Iterator;
    import java.util.Set;
    import javax.swing.JFrame;
    import javax.swing.JScrollPane;
    import javax.swing.JTextArea;
    import javax.swing.JTextField;
    import javax.swing.SwingUtilities;
    public class Client extends JFrame  {
         private String host = "localhost";
         private int port = 5001;
         private SocketChannel socketChannel;
         private Selector selector;
         public void work() {
              try {
                   socketChannel = SocketChannel.open();
                   socketChannel.configureBlocking(false);
                   InetSocketAddress isa = new InetSocketAddress(host, port);
                   socketChannel.connect(isa);
                   selector = Selector.open();
                   int interest = 0;
                   if(socketChannel.isConnected())interest = SelectionKey.OP_READ;
                   else if(socketChannel.isConnectionPending())interest = SelectionKey.OP_CONNECT;
                   socketChannel.register(selector, interest);
                   while(true)
                        int nn = selector.select();
                        System.out.println("nn="+nn);
                        Set keys = selector.selectedKeys();
                        for(Iterator i = keys.iterator(); i.hasNext();)
                             SelectionKey key = (SelectionKey) i.next();
                             i.remove();
                             if (key.isConnectable())
                                  SocketChannel keyChannel = (SocketChannel) key.channel();
                                  System.out.println("Connected "+keyChannel.finishConnect());
                                  key.interestOps(SelectionKey.OP_READ);
                             if (key.isReadable())
                                  SocketChannel keyChannel = (SocketChannel) key.channel();
                                  String m = Help.read(keyChannel);
                                  display(m);
              } catch (IOException e) {
                   e.printStackTrace();
         private void display(final String m) {
              SwingUtilities.invokeLater(new Runnable() {
                   public void run() {
                        area.append(m+"\n");
                        textFieed.setText("");
         private void sendMessage(final String m) {
              Thread t = new Thread(new Runnable() {
                   public void run() {
                        try {
                             Help.write(m, socketChannel);
                        } catch (IOException e) {
                             e.printStackTrace();
              t.start();
         public Client() {
              addWindowListener(new WindowAdapter() {
                   public void windowClosing(WindowEvent e) {
                        System.exit(1);
              textFieed.addKeyListener(new KeyAdapter() {
                   public void keyPressed(KeyEvent e) {
                        if (e.getKeyCode()== KeyEvent.VK_ENTER) {
                             String m = textFieed.getText();
                             sendMessage(m);
              area.setEditable(false);
              getContentPane().add(textFieed, "North");
              getContentPane().add(new JScrollPane(area));
              setBounds(200, 200, 400, 300);
              show();
         private String messageToSend;
         private JTextArea area = new JTextArea();
         JTextField textFieed = new JTextField();
         public static void main(String[] args) {
              Client s = new Client();
              s.work();

  • ByteArray to String and String to ByteArray  error at readUTF from datainpu

    hi everybody this is my first post I hope I can find the help I need I have been doing some research and couldnt find the solution thanks in advanced
    The Objective:
    im building a client server application with java and I need to send a response from the server to the client via Socket
    so the response is like this : <Signal : ByteArray> where Signal is a String so the client can Identify the Type of response
    and the ByteArray is an Array of bytes containing the Information I need
    The Problem:
    I have an Array of bytes containing the info to send and I need to pass this byte[] to a String add some String that let me Identify the data in the client side then remove the identifier in the client side and convert the resulting String back to an array of bytes this doesnt work
    The Code:
    Server Side (Creating the Byte Array):
    public byte[] createData(){
                    ByteArrayOutputStream baos = new ByteArrayOutputStream();
                    DataOutputStream dos = new DataOutputStream(baos);               
                    dos.writeUTF(requestedFile.getName());
                    dos.flush();
                    byte[] data = baos.toByteArray();
                    return data;
    }Server Side (Converting the byte[] to String and Add some Identifier)
    byte[] data= createData(); //Obtain the data  in a byte[]
    String response = new String(data);  //Convert the Data to String
    String Identifier= "14"; // to identify in the client side the data received this will be removed later
    response = Identifier+response;  // add the identifier to the String
    sendToClient( response.getBytes() );  //obtain bytes from the complete Response and send them to clientClient Side ( Receive the response that is a byte array containing the identifier plus the info <Identifier : info> )
                int index=response.indexOf(":")+1;  //find the index of the : so i can delete the identifier
                response=response.substring(index); // delete the identifier
                byte[] data = response.getBytes(); // obtains the bytes for the info ONLY cause the string no longer has identif
                receiveData ( data ); // send the data to be read by this method Client Side (Receive the Info sent from the server and read it)
                public void receiveData ( byte[] data ) {
                   ByteArrayInputStream bais = new ByteArrayInputStream ( data );
                   DataInputStream dis= new DataInputStream ( bais );
                   setTotalSize ( dis.readUTF( ) ); // here is the error  it catches an EndOfFileException without read the info
                }im tried sending other values like long and int and i was able to read them but the problem is with the Strings at the ReadUTF()
    Im tried to be the most clear as possible please help me this is driving me nuts
    and I would really appreciatte all your comments thanks

    lemaniak wrote:
    The Objective:
    im building a client server application with java and I need to send a response from the server to the client via Socket
    so the response is like this : <Signal : ByteArray> where Signal is a String so the client can Identify the Type of response
    and the ByteArray is an Array of bytes containing the Information I need
    The Problem:
    I have an Array of bytes containing the info to send and I need to pass this byte[] to a String add some String that let me Identify the data in the client side then remove the identifier in the client side and convert the resulting String back to an array of bytes this doesnt workFirst of all, well done: a nicely explained problem. I wish more people were as clear as you.
    Second: I'm no expert on this stuff, so I may well be wrong, but I did note the following:
    1. I can't see anywhere where you're putting out the ":" to separate your signal.
    2. You seem to be doing an awful lot of conversions from Strings to bytes and vice-versa, but only your filename is specified as a UTF-8 conversion. Could you not do something like:
    dos.writeUTF("14:" + requestedFile.getName());or indeed, more generically
    dos.writeUTF(signal + ":" + messageBody);from inside a createMessage() method.
    3. You haven't included the sendToClient() code, but your createData() looks suspiciously like what I would put in a method like that.
    From what I understand, you usually want mirror-images of your streams at your sending and receiving ends, so if your client is expecting an DataInputStream wrapping a ByteArrayInputStream to be read via readUTF(), your server better be sending a ByteArrayOutputStream wrapped in a DataOutputStream created, in its entirety, by writeUTF().
    But after your UTF conversion, you're adding your signal and then using String.getBytes(), which uses the default character set, not UTF.
    HIH (and hope I'm right :-))
    Winston

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