Help "ascending" to Java NIO

Hello there.
I've been using Java for quite some time, but the few really networked client/server applications I have used, have used java.io and java.net. Now, even I have heard the rumours about Java NIO, and I am curious. I have tried reading up and down the API on java.nio.* , but I must say I am still kind of confused.
Basically, I am looking for some example code, or a thorough explanation of how all the classes and components come together to form efficient asynchronous non-blocking I/O.
What I picture is a server over TCP/IP meant to handle 100+ clients, written with an emphasis on performance. Think MMORPG, I guess (no no, I am not ambitious enough to want to write one, but I can imagine that gives a good analogy of how I would have the communication set up). The server needs to quickly figure out which clients need to be handled at any given time, with as little overhead or reduntant iteration as possible.
Ok, I am asking alot perhaps.. I just wonder if anyone could offer links to example source-code, write something to show me, or basically just try to explain to me how this all works.
I would be very very grateful if anyone stepped up to the plate.
Thanks,
-Terje

Take a look at my thread Taming the NIO Circus. It starts with simple examples of a single thread echo server and a swing client.

Similar Messages

Need help with java.nio.socket program.

Can someone please help me here? I am trying to create a class that listens on a socket for an incoming connection, but I am getting the following error on compile:
SocketIn.java:48: incompatible types
found : java.nio.channels.SocketChannel
required: java.net.Socket
Socket requestSocket = requestChannel.accept();
Here is my code:
package NETC;
import java.net.*;
import java.util.*;
import java.io.*;
import java.nio.*;
import java.nio.charset.*;
import java.nio.channels.*;
import java.nio.channels.spi.*;
public class SocketIn{
     // Buffer for any incoming data.
     private static ByteBuffer inBuffer = ByteBuffer.allocateDirect(1024);
     CharBuffer charBuffer = null;
     public SocketIn(int intPort)throws Exception{
          // Create a non-blocking server socket.
          ServerSocketChannel serverChannel = ServerSocketChannel.open();
          serverChannel.configureBlocking(false);
          // Use the host and port to bind the server socket.
          InetAddress inetAddress = InetAddress.getLocalHost();
          InetSocketAddress socketAddress = new InetSocketAddress(inetAddress, intPort);
          serverChannel.socket().bind(socketAddress);
          // The selector for incoming requests.
          Selector requestSelector = SelectorProvider.provider().openSelector();
          // Put the server socket on the selectors 'ready list'.
          serverChannel.register(requestSelector, SelectionKey.OP_ACCEPT);
          while(requestSelector.select() > 0){
               System.out.println("Connection Accepted...");
               // A request has been made and is ready for IO.
               Set requestKeys = requestSelector.selectedKeys();
               Iterator iterator = requestKeys.iterator();
               while(iterator.hasNext()){
                    SelectionKey requestKey = (SelectionKey)iterator.next();
                    // Get the socket that's ready for IO.
                    ServerSocketChannel requestChannel = (ServerSocketChannel)requestKey.channel();
                    // This shouldn't block.
                    Socket requestSocket = requestChannel.accept();
                    inBuffer.clear();
                    requestSocket.read(inBuffer);
                    inBuffer.flip();
                    Charset charset = Charset.forName("ISO-8859-1");
                    CharsetDecoder decoder = charset.newDecoder();
                    charBuffer = decoder.decode(inBuffer);
                    iterator.remove();
}

Well its been about a month and a half so I guess you have your answer. In case you don't...
// This shouldn't block.
Socket requestSocket = requestChannel.accept();
The problem is quite simple. The ServerSocketChannel.accept() returns a SocketChannel. (Channel -> Channel).
You can get access to the socket using the SocketChannel.
SocketChannel requestSocketChannel = requestChannel.accept();
Socket requestSocket = requestSocketChannel.socket();
But you don't need the socket to read and write.

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();

Problematic frame: # J java.nio.MappedByteBuffer.load()

Helo all...
I'm getting an error when generating a PDF using BIRT Framework in Eclipse. Nothing fancy, just compiling a simple report to pdf.
The problem is, the JVM crashes with the following error:
# A fatal error has been detected by the Java Runtime Environment:
# EXCEPTION_IN_PAGE_ERROR (0xc0000006) at pc=0x0190f0be, pid=5848, tid=2392
# JRE version: 7.0_09-b05
# Java VM: Java HotSpot(TM) Client VM (23.5-b02 mixed mode, sharing windows-x86 )
**# Problematic frame:
# J java.nio.MappedByteBuffer.load()Ljava/nio/MappedByteBuffer;**
# Failed to write core dump. Minidumps are not enabled by default on client versions of Windows
# An error report file with more information is saved as:
# C:\Users\luis\Desktop\teste\birt\hs_err_pid5848.log
# If you would like to submit a bug report, please visit:
# http://bugreport.sun.com/bugreport/crash.jsp
I already tried:
1. Run the program in another computers - it worked
2. Reinstall Java on the computer - It did nothing
3. I check the integrity of the disk C: - Nothing
I already spent two days trying to fix this and I don't have any progress. I can't find a solution on the web either.
Thanks in advance

Thanks for the help.
But it can not be related to BIRT because it works in every other computer that I tried so far. There is only one computer that not works properly.
If it were BIRT's fault, it wouldn't work in any computer.
Thanks again

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.

Converting from CP1252 (Windows) to ISO 8859-1 doesn't work with java.nio?

Hi
I'm trying to write some code that checks whether an InputStream contains only characters with a given encoding. I'm using java.nio for that. For tests, I downloaded some character set examples from http://www.columbia.edu/kermit/csettables.html
When creating the CharsetDecoder, I want to get all errors:
    Charset charset = Charset.forName( encoding );
    CharsetDecoder decoder = charset.newDecoder();
    decoder.onMalformedInput( CodingErrorAction.REPORT );
    decoder.onUnmappableCharacter( CodingErrorAction.REPORT );I then read an InputStream and try to convert it. If that fails, it can't contain the desired encoding:
    boolean isWellEncoded = true;
    ByteBuffer inBuffer = ByteBuffer.allocate( 1024 );
    ReadableByteChannel channel = Channels.newChannel( inputStream );
    while ( channel.read( inBuffer ) != -1 )
      CharBuffer decoded = null;
      try
        inBuffer.flip();
        decoded = decoder.decode( inBuffer );
      catch ( MalformedInputException ex )
        isWellEncoded = false;
      catch ( UnmappableCharacterException ex )
        isWellEncoded = false;
      catch ( CharacterCodingException ex )
        isWellEncoded = false;
      if ( decoded != null )
        LOG.debug( decoded.toString() );
      if ( !isWellEncoded )
        break;
      inBuffer.compact();
    channel.close();
    return isWellEncoded;Now I want to check whether a file containing Windows 1252 characters is ISO-8859-1. From my point of view, the code above should fail when it gets to the Euro symbol (decimal 128), since that's not defined in ISO-8859-1.
But all I get is a ? character instead:
(}) 125 07/13 175 7D                 RIGHT CURLY BRACKET, RIGHT BRACE
(~) 126 07/14 176 7E                 TILDE
[?] 128 08/00 200 80 EURO SYMBOL
[?] 130 08/02 202 82 LOW 9 SINGLE QUOTEI also tried to replace the faulty character, using
    decoder.onUnmappableCharacter( CodingErrorAction.REPLACE );
    decoder.replaceWith("!");but I still get the question marks.
I'm probably doing something fundamentally wrong, but I dont get it :-)
Any help is greatly appreciated!
Eric

As a suggestion....create a complete example demonstrating the problem. It shouldn't have channel in it since that wouldn't appear to be the problem (decoding is.) You should create the byte array in the example code - populate it with the byte sequence that you think should work. And your code should then demonstrate that it doesn't. Then post that.

Thread blocking on java.nio.charset.CoderResult

Hello all,
I have a multi-threaded app which does some fairly intestive string operations (basically extracts text from documents for indexing a search system).
I am seeing a massive bottleneck around the java.nio.charset.CoderResult class. When profiling, I see a whole stack of threads blocking on (waiting for) a monitor on this java.nio.charset.CoderResult class. Seems to be a result of string encoding/decoding (I am often encoding strings as UTF-8).
Anyone know why the JVM would want my threads to sync on this class? It's creating a huge performance issue for my app. Approximately 15% of ALL the processing time is spent waiting for this class.
Help!

I would guess that you're using some of the static methods in the CoderResult class. The static methods CoderResult.unmappableCache(), CoderResult.malformedForLength() and CoderResult.malformedCache all use a static inner class called Cache. Its get() method is synchronized on Cache.class. Since the Cache inner-class is static, any part of your multi-threaded application that goes through the Cache.get() method is going to be waiting for the lock on Cache.class.
Could you create a CoderResult instance for each thread? That would mean that there would be a different static Cache class for each thread, reducing the number of threads competing for the Cache.class lock.
I'd have to see some of your code to give a better answer.
Brian

Where I can find good Java NIO tutorial?

Please, help me, where I can find good Java NIO tutorial?
thnx.

http://java.sun.com/j2se/1.4.2/docs/guide/nio/

Java NIO's puzzle

hi,all
In traditonal thread-pool based programming way,the Server can process multi-clients by thread(time-sharing),all clients's time is equal.
In Java NIO programming way,the [select] will process multi-clients without thread pool.So,the the second client must be processed after the first client be complished.if the first client is cost much time,other cients must be long time waiting?
plz help me - thanks for your time
Tony.
Hangzhou,china

As an NIO server in non-blocking mode obviously never blocks (or rather it only blocks in select(), when nothing is happening), it can implement any kind of scheduling it likes between the various SocketChannels it has accepted as connected clients. It isn't obliged in any way to completely finish with one client before starting on the next, and it generally can't do so because data from any particular client doesn't necessarily arrive in a single chunk.

Java.nio package

Is there a good tutorial somewhere which explain in depth the new I/O package in JDK 1.4 java.nio?

And there is the JavaWorld article at:
http://www.javaworld.com/javaworld/jw-09-2001/jw-0907-merlin.html
but the example code they give is a little broken, and
the article is also a little confusing. But it can help a little.
I have also started some threads on these forums about the bugs in that article.

Java.nio.BufferOverflowException on big Strings ( 87MB)

Hi!
When calling getBytes() on a big String the following exception is thrown:
java.nio.BufferOverflowException
     at java.nio.charset.CoderResult.throwException(Unknown Source)
     at java.lang.StringCoding$CharsetSD.decode(Unknown Source)
     at java.lang.StringCoding.decode(Unknown Source)
     at java.lang.StringCoding.decode(Unknown Source)
     at java.lang.String.<init>(Unknown Source)
     at java.lang.String.<init>(Unknown Source)
     at com.db.janus.Janus.main(Janus.java:99)
This happens as soon as the size of the String gets bigger than 92003848 bytes.
I can reproduce it with the following code:
String x = new String(new byte[92003848]); // --> OK
String x = new String(new byte[92003849]); // --> Exception
JDK Version: 1.4.2_06
OS: Windows XP
Is this a known bug / limitation? I found a similar bug related to Java on Linux / Solaris, but this one was about getBytes() with Strings > 16MB.
Thanks for your help!

Is there any alternative to solve this problem.I am getting the error
java.nio.BufferOverflowException .This happens in my mail server when the file six\ze of xml where i have stored data about spam/nonspam grows upto 22mb.I have stored this xml in database as blob.at server startup uploading in in my class.Keeps througout in JVM after every 50 th request saving information back to database(about spam/nonspam).Now if xml size grows i am storing this in string to parse etc.it gives this bug error.Sholud i cahnge my datatype or use something as XML Parser to split my xml in pieces(mechanism i am not aware of at all) so that string just takes some size of xml (but here can i use string builder etc.). Now is there any proper solution to this kind of problem whenever i removes some daya from xml spam mail goes to inbox and vice versa.
Please suggest me some solution if possible.
complete error is:
Servlet initialization failed:
java.nio.BufferOverflowException
at java.nio.charset.CoderResult.throwException(CoderResult.java:259)
at java.lang.StringCoding$CharsetSD.decode([BII)[C(Unknown Source)
         at java.lang.StringCoding.decode(Ljava.lang.String;[BII)[C(Unknown Source)
         at java.lang.String.<init>([BIILjava.lang.String;)V(Unknown Source)
         at java.lang.String.<init>([BLjava.lang.String;)V(Unknown Source)
         at zerocode.core.ByteBlock.toString(ByteBlock.java:89)
         at zcCollab.mailProcessing.NaiveBayesClassifier._getInstanceData(NaiveBayesClassifier.java:275)
         at zcCollab.mailProcessing.NaiveBayesClassifier.initialize(NaiveBayesClassifier.java:86)
         at zcCollab.mailProcessing.SimpleDeliveryManager._setupClassifiers(SimpleDeliveryManager.java:409)
         at zcCollab.mailProcessing.SimpleDeliveryManager.<init>(SimpleDeliveryManager.java:62)
         at zcCollab.zcApp.InfoManagerApp._createDeliveryProcessor(InfoManagerApp.java:307)
         at zcCollab.zcApp.InfoManagerApp.initialize(InfoManagerApp.java:294)
         at zerocode.udm.Application._createInstance(Application.java:168)
         at zerocode.udm.Application.createInstanceForServlet(Application.java:111)
         at zerocode.servlet.UdmServlet._createApplication(UdmServlet.java:67)
         at zerocode.servlet.UdmServlet._initialize(UdmServlet.java:52)
         at zerocode.servlet.GenericServlet.init(GenericServlet.java:116)
         at org.mortbay.jetty.servlet.ServletHolder.getServlet(ServletHolder.java:292)
         at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:329)
         at org.mortbay.jetty.servlet.ServletHandler.dispatch(ServletHandler.java:657)
         at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:567)
         at org.mortbay.http.HttpContext.handle(HttpContext.java:1808)
         at org.mortbay.http.HttpContext.handle(HttpContext.java:1758)
         at org.mortbay.http.HttpServer.service(HttpServer.java:879)
         at org.mortbay.http.handler.ForwardHandler.handle(ForwardHandler.java:130)
         at org.mortbay.http.HttpContext.handle(HttpContext.java:1808)
         at org.mortbay.http.HttpContext.handle(HttpContext.java:1758)
         at org.mortbay.http.HttpServer.service(HttpServer.java:879)
Thanks
Vijendra

Java.nio and databases

Please, need help.
I'm using java.nio to get large files contents (txt) and need to put these data into MSSQL SERVER 2000 database tables. NIO have capabilityies to get data and transfer directly to the tables? If so, how can i do it?
Thanks a lot
Aloisio

ChuckBing, i'm connected with database trough JDBC yet and i can retrieve data meaning my connection is OK.
I'm able to read data from a txt file (250mb large) trough MappedByteBuffer and write into another with the same size and content. It's working fine.
My question is if i can read the txt file and, instead write the data into another txt file, put these data into a table.
Thanks for your reply

Java.nio.channels.ClosedChannelException using https

Hello,
I have deployed an application to the OC4J 10.1.3.40, it runs well as long as it is used by http. Since it is running under https an error comes randomly.
Here is the text from the log.xml:
<MSG_TEXT>Exception in NIOServerSocketDriver:selectForRead</MSG_TEXT>
<SUPPL_DETAIL><![CDATA[java.nio.channels.ClosedChannelException
     at java.nio.channels.spi.AbstractSelectableChannel.configureBlocking(AbstractSelectableChannel.java:252)
     at oracle.oc4j.network.NIOServerSocketDriver$SelectorThreadTask.selectForRead(NIOServerSocketDriver.java:331)
     at oracle.oc4j.network.NIOServerSocketDriver.selectForRead(NIOServerSocketDriver.java:58)
     at oracle.oc4j.network.ServerSocketAcceptHandler.persistConnection(ServerSocketAcceptHandler.java:389)
     at oracle.oc4j.network.ServerSocketAcceptHandler.endReadHandlerRun(ServerSocketAcceptHandler.java:409)
     at oracle.oc4j.network.ServerSocketReadHandler$SafeRunnable.run(ServerSocketReadHandler.java:275)
     at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:303)
     at java.lang.Thread.run(Thread.java:619)
]]></SUPPL_DETAIL>
Can anybody help me?
Regards
Jens

Jens,
Can you turn up your debug level to FINEST? It appears that during the read operation an attempt to access a channel closed to read occurs.
// Create binding -- set binding properties before you open the factory.
OracleDBBinding odbBinding = new OracleDBBinding();
// Create address.
EndpointAddress odbAddress = new EndpointAddress("oracledb://ADAPTER/");
// Create channel factory from binding and address.
ChannelFactory<IRequestChannel> factory =
    new ChannelFactory<IRequestChannel>(odbBinding, odbAddress);
// Specify credentials.
factory.Credentials.UserName.UserName = "SCOTT";
factory.Credentials.UserName.Password = "TIGER";
// Open factory
factory.Open();
// Get channel and open it.
IRequestChannel channel = factory.CreateChannel();
channel.Open();-Michael

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;
public class TimeLineTest {
     private static final int BYTE_LENGTH = 1000;
     //this is the input
     static byte[] b = new byte[BYTE_LENGTH];
     public static void main(String[] arg) throws Exception
          //initializing the input
          for (int i=0;i<BYTE_LENGTH;i++)
               b[i] = 0;
          File file = new File(arg[0]);
          RandomAccessFile raFile = new RandomAccessFile(file,"rw");
          FileChannel fChannel = raFile.getChannel();
          int loopCount = 1000000;
          MappedByteBuffer mbuffer = fChannel.map( FileChannel.MapMode.READ_WRITE ,0,loopCount * BYTE_LENGTH);
          //System.out.println(" going to fill in a file" + file.getName());
          long k = 0;
          long startTime = System.currentTimeMillis();
          for (int i=0;i<loopCount;i++)
     //populate the mapped buffer
               mbuffer.put(b);
          //persist into the file
          mbuffer.force();
          long endTime = System.currentTimeMillis();
          System.out.println(" file filled size1 "+file.length());
          System.out.println(" time " + (endTime - startTime));
On a linux machine this takes around 7 secs while dd used as
"dd if=/dev/zero of=mytestfile.out bs=1000 count=1000000"
1000000+0 records in
1000000+0 records out
1000000000 bytes (1.0 GB) copied, 4.618 seconds, 217 MB/s
4.6 and 7 differ quite a lot. Is there a way the java code can be improved to match dd ?(-sever does not help)
Thanks
Sumanta

Hi
Can this be called a dd equivalent code ?
package filePersistence.test;
import java.io.File;
import java.io.FileOutputStream;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
public class TimeLineTest {
     private static final int BYTE_LENGTH = 1000;
     //this is the input
     static byte[] b = new byte[BYTE_LENGTH];
     public static void main(String[] arg) throws Exception
          //initializing the input
          for (int i=0;i<BYTE_LENGTH;i++)
               b[i] = 0;
          String srcFile = arg[0] + "_src";
          FileOutputStream fos = new FileOutputStream(srcFile);
          fos.write(b);
          fos.getFD().sync();
          fos.flush();
          fos.close();
          RandomAccessFile srcraFile = new RandomAccessFile(srcFile,"rw");
          FileChannel srcChannel = srcraFile.getChannel();
          File file = new File(arg[0]);
          RandomAccessFile raFile = new RandomAccessFile(file,"rw");
          FileChannel raChannel = raFile.getChannel();
          int loopCount = 1000000;
          //MappedByteBuffer mbuffer = fChannel.map( FileChannel.MapMode.READ_WRITE ,0,loopCount * BYTE_LENGTH);
          //System.out.println(" going to fill in a file" + file.getName());
          long startTime = System.currentTimeMillis();
          for (int i=0,position=0;i<loopCount;i++,position+=BYTE_LENGTH)
     //populate the mapped buffer
               //mbuffer.put(b);
               raChannel.position(position);
               srcChannel.transferTo(0, BYTE_LENGTH, raChannel);
          //persist into the file
          //mbuffer.force();
          raFile.getFD().sync();
          raChannel.close();
          raFile.close();
          long endTime = System.currentTimeMillis();
          System.out.println(" file filled size1 "+file.length());
          System.out.println(" time " + (endTime - startTime));
}

Any java.nio guru out there ?

Hi help,
I'm studying new java.io classes. I've compiled and learnt
a basic server like this...
import java.io.*;
import java.net.*;
import java.nio.*;
import java.nio.channels.*;
import java.util.*;
public class Server {
   private static int port = 9999;
   public static void main(String args[])
     throws Exception {
     Selector selector = Selector.open();
     ServerSocketChannel channel =
       ServerSocketChannel.open();
     channel.configureBlocking(false);
     InetSocketAddress isa = new InetSocketAddress(port);
     channel.socket().bind(isa);
     // Register interest in when connection
     channel.register(selector, SelectionKey.OP_ACCEPT);
     // Wait for something of interest to happen
     while (selector.select() > 0) {
       // Get set of ready objects
       Set readyKeys = selector.selectedKeys();
       Iterator readyItor = readyKeys.iterator();
       // Walk through set
       while (readyItor.hasNext()) {
         // Get key from set
         SelectionKey key =
           (SelectionKey)readyItor.next();
         // Remove current entry
         readyItor.remove();
         if (key.isAcceptable()) {
           // Get channel
           ServerSocketChannel keyChannel =
             (ServerSocketChannel)key.channel();
           // Get server socket
           ServerSocket serverSocket = keyChannel.socket();
           // Accept request
           Socket socket = serverSocket.accept();
           // Return canned message
           PrintWriter out = new PrintWriter
             (socket.getOutputStream(), true);
           out.println("Hello, NIO");
           out.close();
         } else {
           System.err.println("Ooops");
     // Never ends
} now I'd like to write a Proxy Server. In other
words the Server must
1. listen for a request
2. forward the request to another server
3. listen its reply
4. forward it back to the original caller.
I've tried to modify the basic class but with no success....
unfortunately I'm not that smart with these new Apis.
anybody can give me some guidelines about how should I
struct it ?
Thanks a lot
Francesco

Not a guru but I'll offer some suggestions. Are these persistent connections to the proxy, or is a connection made per request? You'll probably do things a little bit differently in the two different cases.
In general though, you can have one thread running a request dispatcher which accepts incoming connections and puts read ready channels on a queue. Another thread(or threads) can take requests off the queue and process them. Also, when you accept new connections, I think its better to do it through channels, rather than work directly with the socket. Something like this:
SocketChannel clientChannel = serverChannel.accept();
clientChannel.configureBlocking(false);
SelectionKey newReadKey = clientChannel.register(selector, SelectionKey.OP_READ);
Where are you getting into problems?

Help "ascending" to Java NIO

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