Java NIO - copy-on-write buffer

This is regarding peculiar behavior of a Java program on Linux-IA64 platform.
I have a Java program that uses MappedByteBuffer. For the same file, there are three buffers - read only, read/write and copy-on-write (cow)
First, change contents of cow buffer and print all buffers. The change is reflected only in cow buffer (not in ro or rw) - as expected.
Then, change contents of r/w buffer and print all buffers. The change is NOT observed in cow buffer, but reflected in ro and rw buffers (for Linux-IA64). I tried the same program in Linux-X86 and the change is reflected in all buffers (including cow buffer).
I used JDK 1.4.2_03 for compiling and running. The doc for MappedByteBuffer says
"The content of a mapped byte buffer can change at any time, for example if the content of the corresponding region of the mapped file is changed by this program or another. Whether or not such changes occur, and when they occur, is operating-system dependent and therefore unspecified."
Is this behaviour acceptable? Is this observed in any other platform?
I think Java NIO leaves it to the O/S and JVM is not doing anything here (as different from java.io). This could probably result in inconsistent behaviour across platforms (though it improves performance)
Please let me know your thoughts.

My thought is that you have posted this to the wrong forum.

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Java.nio read/write question

Hello,
I just started to learn the java.nio package so I decided to make a simple Echo server. I made a client which reads a line from the keyboard, sends it to the server and the server returns it. It all works except one little detail. Here's little code from the server:
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Files.copy java.nio.file.AccessDeniedException

Hello everybody,
I hope you are well, Me not.
I use this method to unzip
public void deziper(final Path zipFile, final Path destDir) throws IOException*
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Replace all files work well, but when application try to replace Executable Jar File in same directory This error is thrown
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Thank you very match
Edited by: 964115 on Oct 9, 2012 5:39 AM
Edited by: 964115 on Oct 9, 2012 5:40 AM
Edited by: 964115 on Oct 9, 2012 5:46 AM
Edited by: 964115 on Oct 9, 2012 5:55 AM

Looks like you are trying to move the jar file you are executing and Windows has placed a lock on it. As far as I am aware there is no simple way round this. Why do you think you need to do this?

Java NIO client

I need to make the server is able to hold about 500 connections and operates on a single thread. The server itself should make all the connections. Where can I find examples of finished implementations?

I have an example, but it does not work
import java.io.IOException;
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import java.net.InetSocketAddress;
import java.net.Socket;
import java.nio.ByteBuffer;
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                         if (key.isConnectable()) {
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               key.cancel();
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Edited by: 915967 on 01.08.2012 7:07

Performance of java nio with dd in linux.

Hi
I ran this code in java to dump 0s in a file of size 1gb and tried the same with dd in linux.
Java code : I use a preinitialized array (the data) and fill a mappedbytebuffer with it.
package filePersistence.test;
import java.io.File;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
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On a linux machine this takes around 7 secs while dd used as
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1000000+0 records in
1000000+0 records out
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Thanks
Sumanta

Hi
Can this be called a dd equivalent code ?
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Using java.nio

I have copied this, one program from a book that would have to read file of gives to me to you mixed but it does not work, you could me why?
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import java.io.IOException;
import java.io.File;
import java.io.FileNotFoundException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
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public static void main(String[] args) {
File aFile = new File("C:/Beg Java Stuff/primes.txt");
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try {
inFile = new FileInputStream(aFile);
} catch(FileNotFoundException e) {
e.printStackTrace(System.err);
System.exit(1);
FileChannel inChannel = inFile.getChannel();
try {
ByteBuffer lengthBuf = ByteBuffer.allocate(8);
int strLength = 0; // Stores the string length
ByteBuffer buf = null; // Stores a reference to the second byte buffer
byte[] strChars = null; // Stores a reference to an array to hold the string
while(true) {
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lengthBuf.flip();
strLength = (int)lengthBuf.getDouble(); // Extract the length and convert to int
buf = ByteBuffer.allocate(strLength+8); // Buffer for the string & the prime
if(inChannel.read(buf) == -1) { // Read the string & binary prime value
assert false; // Should not get here!
break; // Exit loop on EOF
buf.flip();
strChars = new byte[strLength]; // Create the array for the string
buf.get(strChars); // Extract string & binary prime value
System.out.println("String length: " + strChars.length+ " String: " +
new String(strChars) + " Binary value: " + buf.getLong());
lengthBuf.clear(); // Clear the buffer for the next read
System.out.println("\nEOF reached.");
inFile.close(); // Close the file and the channel
} catch(IOException e) {
e.printStackTrace(System.err);
System.exit(1);
System.exit(0);
This e' the program that writes the file
import java.io.*;
import java.nio.*;
import java.nio.channels.FileChannel;
public class PrimesToFile2 {
public static void main(String[] args) {
int primesRequired = 100; // Default count
if (args.length > 0) {
try {
primesRequired = Integer.valueOf(args[0]).intValue();
} catch (NumberFormatException e) {
System.out.println("Prime count value invalid. Using default of "
+ primesRequired);
long[] primes = new long[primesRequired]; // Array to store primes
primes[0] = 2; // Seed the first prime
primes[1] = 3; // and the second
// Count of primes found - up to now, which is also the array index
int count = 2;
long number = 5; // Next integer to be tested
outer:
for (; count < primesRequired; number += 2) {
// The maximum divisor we need to try is square root of number
long limit = (long) Math.ceil(Math.sqrt((double) number));
// Divide by all the primes we have up to limit
for (int i = 1; i < count && primes[i] <= limit; i++)
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continue outer; // yes, try the next number
primes[count++] = number; // We got one!
File aFile = new File("C:/Beg Java Stuff/primes.txt");
FileOutputStream outputFile = null;
try {
outputFile = new FileOutputStream(aFile);
} catch (FileNotFoundException e) {
e.printStackTrace(System.err);
System.exit(1);
FileChannel file = outputFile.getChannel();
final int BUFFERSIZE = 100; // Buffer size in bytes
ByteBuffer buf = ByteBuffer.allocate(BUFFERSIZE);
DoubleBuffer doubleBuf = buf.asDoubleBuffer();
buf.position(8);
CharBuffer charBuf = buf.asCharBuffer();
LongBuffer longBuf = null;
String primeStr = null;
for (int i = 0; i < primes.length; i++) {
primeStr = "prime = " + primes; // Create the string
doubleBuf.put(0,(double) primeStr.length());// Store the string length
charBuf.put(primeStr); // Store the string
buf.position(2 * charBuf.position() + 8); // Position for 3rd buffer
longBuf = buf.asLongBuffer(); // Create the buffer
longBuf.put(primes[i]); // Store the binary long value
buf.position(buf.position() + 8); // Set position after last value
buf.flip(); // and flip
try {
file.write(buf); // Write the buffer as before.
} catch (IOException e) {
e.printStackTrace(System.err);
System.exit(1);
buf.clear();
doubleBuf.clear();
charBuf.clear();
try {
System.out.println("File written is " + file.size() + " bytes.");
outputFile.close(); // Close the file and its channel
} catch (IOException e) {
e.printStackTrace(System.err);
System.exit(1);
System.exit(0);
This works correctly

I don't have problems when I compile the program but if I run the program ....I have this
String length: 9 String: prim Binary value: 7277852183226228736
String length: 0 String: Binary value: 162166969980682240
String length: 0 String: Binary value: 7854388801345436928
String length: 0 String: Binary value: 3573983215616
Stjava.lang.IllegalArgumentException
at java.nio.ByteBuffer.allocate(ByteBuffer.java:303)
at ReadPrimesMixedData.main(ReadPrimesMixedData.java:35)
ring length: 0 String: Binary value: 7566167222444367872
String length: 0 String: Binary value: 88089088
String length: 0 String: Binary value: 8214681170873443584
String length: 0 String: Binary value: 1856
String length: 0 String: Binary value: 8070575878335130880
Exception in thread "main"

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

Hello,
I'm developing a simple chat application who echo messages
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// SERVER
package test;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
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import java.util.Iterator;
import java.util.Set;
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                         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();

[java.nio] StreamCorruptedException when deserializing objects

Hello everybody!
I made a messaging (chat) program using java.io where all the client-server communication is done by serializing small objects. Now I would like to covert the server side to the NIO concept and I'm already struck. I successfully pass objects to the client and the client deserializes them, but only the first one! When it try to read the second it fails with a StreamCorruptedException.
Here�s a sample (testing) code. In the server run() method I first serialize a string, then get its byte array from ByteArrayOutputStream and in the loop periodically send this byte array through the channel. On the client side I just read the deserialized object.
Server run():
public void run() {
        try {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(baos);
            oos.writeObject("abcdefgh");
            byte[] objectArr = baos.toByteArray();
            baos.close();
            oos.close();
            ByteBuffer buff = ByteBuffer.allocate(objectArr.length);
            buff.put(objectArr);
            buff.flip();
            while(true) {
                selector.select();
                Set keys = selector.selectedKeys();
                for (Object o : keys) {
                    SelectionKey key = (SelectionKey)o;
                    if (key.isAcceptable()) {
                        ServerSocketChannel server = (ServerSocketChannel) key.channel();
                        clientChannel = server.accept();
                        if (clientChannel == null)
                            continue;
                        clientChannel.configureBlocking(false);
                        SelectionKey clientKey = clientChannel.register(selector, SelectionKey.OP_WRITE);
                    } else if (key.isWritable()) {
                        SocketChannel client = (SocketChannel) key.channel();
                        if (buff.hasRemaining()) {
                            client.write(buff);
                        } else {
                            buff.clear();
                            buff.put(objectArr);
                            buff.flip();
                try {
                    Thread.currentThread().sleep(2000);
                } catch (InterruptedException e) {
                    return;
        } catch (IOException e) {
            e.printStackTrace();
    }Client run():
public void run() {
        try {
            soc = new Socket("localhost", 4000);
            ObjectInputStream ois = new ObjectInputStream(soc.getInputStream());
            while(true) {
                Object d = ois.readObject();
                System.out.println("data = " + d.toString());
        } catch (Exception ex) {
            ex.printStackTrace();
    }At the second read I get a StreamCorruptedException.
Apart from this I would like some hints in how to implement the application with NIO. For example how can I tell the objects apart on the client side � should I send every time a byte array before the object, which tells the length of the next coming object? This is probably not a 100% bulletproof solution and presents additional data transfer?
Than you in advance!

OK, I found a solution but I don't like it, because I don't understand it.
The ObjectOutputStream adds a header (4 bytes) to the stream - if I send the array with those four bytes I get an StreamCorruptedException. If I send the array without the header I also get a StreamCorruptedException: "invalid stream header".
If I reconstruct the object, by calling ObjectOutputStream.writeObject() and get it's byte array from ByteArrayOutputStream.toByteArray(), every time I have to fill the ByteBuffer, then it works.
Here's the modified sending block, for the above example:
} else if (key.isWritable()) {
                        SocketChannel client = (SocketChannel) key.channel();
                        if (buff.hasRemaining()) {
                            client.write(buff);
                        } else {
                            //* ---- added code ---------
                            baos.reset();
                            oos.writeObject("abcdefgh");
                            objectArr = baos.toByteArray();
                            buff.clear();
                            buff.put(objectArr);
                            buff.flip();
                    }   I really don't understand why I have to write the object in the object stream every time. I used ObjectOS and ByteArrayOS, to get the object byte array and then I thought I could forget about those streams and use this array to fill the ByteBuffer. What changes if I send the object through this process with every iteration (and how this harms speed - it's like sending everything twice)? If someone would explain this to me I would appreciate it much.

Java NIO locking and NTFS network resources

Hi all - just ran into a really nasty situation and I was wondering if anyone else has hit it and might have some suggestions.
Platform: JRE 1.4_02 on a Win XP machine
The following test code locks a file, then copies it to another location using NIO.
When I run it with source path on my local drives (C), it works fine. If I run it with source path on a network shared resource, it fails with an IOException with description 'Error performing inpage operation'.
If I disable the lock immediately before the copy operation, it works fine.
My conclusion is that there is something about the NIO locking implementation that prevents it from working properly with NTFS volumes on other hosts. Can this be right? I've found the following bug report:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4774175
but this seems like a huge problem that would prevent folks from using NIO in many, many applications. Maybe I'm wrong on something here...
Anyway, here's the test code:
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
* Created on May 28, 2004
* (c) 2004 Trumpet, Inc.
* @author kevin
public class test {
     private void createFile(File f) throws IOException{
          FileOutputStream os = new FileOutputStream(f);
          for(int i = 0; i < 10; i++){
               os.write(i);
          os.close();
     public test() {
          boolean testWithReleasingLockPriorToCopy = false;
          final File f1= new File("w:/temp/test2.lok");
          final File f2 = new File("w:/temp/test.lok");
          f1.delete();
          f2.delete();
          try {
               createFile(f1);
               RandomAccessFile raf1 = new RandomAccessFile(f1, "rw");
               RandomAccessFile raf2 = new RandomAccessFile(f1, "rw");
               FileChannel ch1 = raf1.getChannel();
               FileChannel ch2 = raf2.getChannel();
               FileLock flock1 = ch1.lock();
              if (!f2.getParentFile().exists() && !f2.getParentFile().mkdirs())
                   throw new IOException("Unable to create directories for destination file '" + f2 + "'");
              if (testWithReleasingLockPriorToCopy)
                   flock1.release();
               ch1.transferTo(0, raf1.length(), ch2);
               raf1.close();
               raf2.close();
          } catch (Exception e) {
               // TODO Auto-generated catch block
               e.printStackTrace();
     public static void main(String[] args) {
          test t = new test();
}Does anyone have any pointers here? I need to be able to exclusively lock a file on a network drive (preventing any other applications from opening it), then make a copy of it. I can't use regular stream operations, because the lock prevents them from working properly (it appears that, once you grab a file lock using NIO, the only way your application can use the file is via the NIO operations - using stream operations fails...).
Thanks in advance for any help!
- Kevin

i've run into the same problem recently, channels working fine for local file locking, but when you turn to the network, they fail to accurately handle locks.
i ended up writing a jni utility to ship with my java application that locks files using native windows calls.
my .c file ends up looking something like this:
JNIEXPORT jint JNICALL Java_Mapper_NativeUtils_LockFile
(JNIEnv *env, jobject obj, jstring filename)
const char* ntvFilename = (*env)->GetStringUTFChars(env, filename, 0);
int retVal = (int)CreateFile
ntvFilename
, GENERIC_WRITE
, FILE_SHARE_READ
, 0
, OPEN_EXISTING
, FILE_FLAG_SEQUENTIAL_SCAN
, 0
//add code to throw java exceptions based on retVal
if (retVal == (int)INVALID_HANDLE_VALUE)
return retVal;
(*env)->ReleaseStringUTFChars(env, filename, ntvFilename);
return retVal;
JNIEXPORT jboolean JNICALL Java_Mapper_NativeUtils_UnlockFile
(JNIEnv *env, jobject obj, jint handle)
     CloseHandle((void *)handle);
return 1;
it's a little shy on the error checking side, but it provides support for network file locking that java seems to lack.

NIO SocketChannel truncating write from MappedByteBuffer

Hello!
I'm running SDK build 1.4.1_01-b01 on Win2K (SP3), but I can also duplicate this on Linux (2.4 kernel).
I'm writing a simple file server, and it uses the following code:FileInputStream fis = new FileInputStream(file);
FileChannel fc = fis.getChannel();
MappedByteBuffer buffer = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());
sc.write(buffer);
sc.close()However applications that download (not just Java applications) do not receive the entire file. The server reports sending all of the bytes (sc.write() returns the value from fc.size()) but it is not all received byt the client downloading (I'm using wget on a Linux box).
NIO has no way to flush, so... ok this is where I'm lost. Am I doing this all wrong?
I even triedsc.socket().getOutputStream().flush();to no avail.
Another similar example of this problem is the code from this article at JavaWorld:
http://www.javaworld.com/javaworld/jw-09-2001/jw-0907-merlin.html
The zip file contains only one class file that runs, except serving up say a 300kB Jar file does not work.

Firstly thankyou very much for your time so far...
I hope I'm not tripping over the protocol, I have implemented a simple HTTP server.
The important section of code (very cut down - no log messages and less Exception handling) is:public class HttpGetHandler extends Thread {
    private SocketChannel sc;
    private File file;
    public HttpGetHandler_1(SocketChannel pSocketChannel, File pFile) {
        super("HttpGetHandler");
        this.sc = pSocketChannel;
        this.file = pFile;
        start();
    public void run() {
        try {
            // Open the file and then get a channel from the stream
            FileInputStream fis = new FileInputStream(file);
            FileChannel fc = fis.getChannel();
            // Get the file's size and then map it into memory
            long sz = (int) fc.size();
            // Create Header
            String header = new String(
            "HTTP/1.0 200 OK\r\n"
            + "Content-Length: " + sz + "\r\n"
            transmitBuffer(ByteBuffer.wrap(header.getBytes()));
            long position = 0;
            while (position < sz) {
                MappedByteBuffer buffer = fc.map(FileChannel.MapMode.READ_ONLY, position, sz - position);
                transmitBuffer(buffer);
                position += buffer.capacity();
        } catch (Exception e) {
        } finally {
            try {
                // HACK
                try {
                    Thread.currentThread().sleep(20000);
                } catch (InterruptedException e) {
                    log.warn("InterruptedException", e);
                sc.close();
            } catch (IOException e) {
    private void transmitBuffer(ByteBuffer pBuffer) throws IOException {
        while (pBuffer.hasRemaining()) {
            sc.write(pBuffer);
}

Java.nio.channels.Pipe?

Someone explain what java.nio.channels.Pipe should be uses for, and how to use it?

You can use this class to transfer the content of a channel from one thread to another thread.
The writing thread blocks when the pipe is full.
package com.desoft.pipetest;
import java.io.*;
import java.nio.*;
import java.nio.channels.*;
public class PipeTest {
public static void main (String args[])
try
FileInputStream fis = new FileInputStream(args[0]);
FileChannel fc = fis.getChannel();
Pipe p = Pipe.open();
PipeReader pr = new PipeReader( p );
Thread t = new Thread( pr );
t.start();
fc.transferTo(0, fc.size(), p.sink() );
catch( IOException ioe )
ioe.printStackTrace();
* Read from a Pipe and write Content to System.out
static class PipeReader implements Runnable
Pipe p;
public PipeReader( Pipe p )
this.p = p;
public void run()
try
ByteBuffer buffer = ByteBuffer.allocate( 10 );
int len = 0;
while( (len=p.source().read( buffer )) > 0 )
buffer.rewind();
for( int i = 0; i < len; i++ )
System.out.print( (char)buffer.get());
buffer.rewind();
catch( IOException ioe )
ioe.printStackTrace();

Socket disconnection event not being reveived java.nio

Hi All
My question is as below
i am using java.nio package + win 2K + jdk1.4.1_02
I have a Server accepting socket connection and is configured
in Nonblocking mode.
-The server receives (selector) events (accept event)
when a client requests for a connection .
-The server is getting read and write events when
client wants to read and write
-The server gets a read event when the client disconnects
My only problem is that the Server is not getting any events
when the client disconnect due to network break down
for EX when the network connection breaks the client disconnects
but the server selector is not getting any events
I am storing the client Socket objects in a Hash Table and
if i execute the .isConnected() method it returns true
even though the the client is down
The only work around is to try to read and write on the socket
i get an IO exception and am able to make out that the
client is disconnected
But this is not desirable for my client
as client modification to give any kind of echo is not possible and
a read /write event will cause problem.
Can any one tell how to detect client side disconnection
with out Read and Write on the client socket
I get an socket Exception when the socket is in Blocking IO and is blocked on read/ write but I am facing this problem in NonBlockingIO
Regards
Avinash

int ct = read.selectNow();
if (ct > 0)
Set readyKeys = read.selectedKeys();
Iterator i = readyKeys.iterator();
while (i.hasNext())
SelectionKey key = (SelectionKey) i.next();
i.remove();
if (key.isReadable())
SelectableChannel nextReady = (SelectableChannel) key.channel();
SocketChannel sc = (SocketChannel) key.channel();
int rd = sc.read(buffer);
// Link is dead
if (rd == -1)
key.cancel();
key.attach(null);
nextReady.close();
continue;
// Process your data
catch (Exception e)
e.printStackTrace();

Java System Copy Error

Hi all. I am trying System Copy.
During the Database Load I became the following Error
"An error occurred while processing service SAP NetWeaver'04 Support Release1> Java System> MS SQL Server> Migration - Target System Installation."
jload.log is:
info: trying to create table IMS_SYNCINXVIEW
com.sap.inst.jload.Jload dbImport
info: table IMS_SYNCINXVIEW created
com.sap.inst.jload.Jload dbImport
warning: DB Error during import of IMS_SYNCINXVIEW
com.sap.inst.jload.Jload printSQLException
warning: Message: The SQL statement "INSERT INTO "IMS_SYNCINXVIEW" ("ACTIVITYID","RESOURCEID","DOCUMENTTYPE","FORMATVERSION") VALUES (?,?,?,?)" contains the semantics error[s]: table "IMS_SYNCINXVIEW" unknown
com.sap.inst.jload.Jload printSQLException
warning: SQLState: SAP06
com.sap.inst.jload.Jload printSQLException
warning: ErrorCode: 1001123
com.sap.inst.jload.Jload dbImport
info: trying to create table J2EE_CONFIG
com.sap.inst.jload.Jload logStackTrace
warning: java.nio.BufferUnderflowException
     at java.nio.Buffer.nextGetIndex(Buffer.java:404)
     at java.nio.HeapByteBuffer.getChar(HeapByteBuffer.java:234)
     at com.sap.inst.jload.io.DataFileEntry.<init>(DataFileEntry.java:52)
     at com.sap.inst.jload.io.DataFile.getNextEntry(DataFile.java:354)
     at com.sap.inst.jload.io.DataFile.findDataEntry(DataFile.java:397)
     at com.sap.inst.jload.db.DBTable.create(DBTable.java:77)
     at com.sap.inst.jload.Jload.dbImport(Jload.java:278)
     at com.sap.inst.jload.Jload.executeJob(Jload.java:397)
     at com.sap.inst.jload.Jload.main(Jload.java:621)
com.sap.inst.jload.db.DBConnection disconnect
info: disconnected

Hi,
I have also faced the same error during system copy, the tables IMS_SYNCINXVIEW, PVC_ACTVERSVIEW, PVC_OBJVERSVIEW which are related to Development Infrastructure. These are bad tables and hence it has to be removed.
I found a file called negativTableListForJload.xml in C:\Program File
sapinst_instdir\NW04S\LM\COPY\MSS\SYSTEM\CENTRAL\AS-JAVA\install\sltools\
The import could be continued after removing the line
     <object name="IMS_SYNCINXVIEW" action="insert"/>
(and of course the corresponding entries for all the other views) from
the file IMPORT.XML
So the steps u have to perform are
Please cancel the Installation by pressing the cancel button and then stop the sapinst and edit these files and again continue the old installation.
1) go to C:\Program File
sapinst_instdir\NW04S\LM\COPY\MSS\SYSTEM\CENTRAL\AS-JAVA
EDIT the IMPORT.XML i.e. delete the line
<object name="IMS_SYNCINXVIEW" action="insert"/>
2) now again got to C:\Program File
sapinst_instdir\NW04S\LM\COPY\MSS\SYSTEM\CENTRAL\AS-JAVA\install\sltools\
edit the negativTableListForJload.xml file. i.e. delete the lines which has the entry for these tables.
3) Restart the installation. Donot retry.
Reward point if u feel so.
cheers
Naveen.H

Using ByteBuffer from java.nio package

Hi,
I have a java.nio.ByteBuffer object that is returned from the C++ code, created using NewDirectByteBuffer. I would like to use this ByteBuffer object in my java code to create a WritableRaster object. I would like to avoid an array copy here as the data may be huge.
Could someone please let me know if there is a solution to this?
Thanks in advance for any help.

Warning: I know almost nothing about the java.awt.image package - so please take what Im going to suggest as the throw away, off the top of my head random rambling that it is......
Could you implement a custom DataBuffer which sits on top of a NIO ByteBuffer? Already, custom DataBuffers provide access for certain data types (e.g. theres a DataBufferByte, DataBufferDouble which wrap arrays) - so I guess you could write a NIODataBufferByte - or what ever - which sits on top of a ByteBuffer.
Im not sure how this would tie in with the SampleModel though (again, I dont know anything about this area).
Hopefully someone who knows this stuff will come across this thread and actually give you some decent advice :o)
~D

Java NIO - copy-on-write buffer

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