GetWebPageApp.java Source code

Introduction

Here is the source code for GetWebPageApp.java

Source

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Set;

public class GetWebPageApp {
    static Selector selector;

    public static void main(String args[]) throws Exception {
        String resource, host, file;
        int slashPos;

        resource = "www.java2s.com/index.htm"; // skip HTTP://
        slashPos = resource.indexOf('/'); // find host/file separator
        if (slashPos < 0) {
            resource = resource + "/";
            slashPos = resource.indexOf('/');
        }
        file = resource.substring(slashPos); // isolate host and file parts
        host = resource.substring(0, slashPos);
        System.out.println("Host to contact: '" + host + "'");
        System.out.println("File to fetch : '" + file + "'");

        SocketChannel channel = null;

        try {
            Charset charset = Charset.forName("ISO-8859-1");
            CharsetDecoder decoder = charset.newDecoder();
            CharsetEncoder encoder = charset.newEncoder();

            ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
            CharBuffer charBuffer = CharBuffer.allocate(1024);

            InetSocketAddress socketAddress = new InetSocketAddress(host, 80);
            channel = SocketChannel.open();
            channel.configureBlocking(false);
            channel.connect(socketAddress);

            selector = Selector.open();

            channel.register(selector, SelectionKey.OP_CONNECT | SelectionKey.OP_READ);

            while (selector.select(500) > 0) {
                Set readyKeys = selector.selectedKeys();
                try {
                    Iterator readyItor = readyKeys.iterator();

                    while (readyItor.hasNext()) {

                        SelectionKey key = (SelectionKey) readyItor.next();
                        readyItor.remove();
                        SocketChannel keyChannel = (SocketChannel) key.channel();

                        if (key.isConnectable()) {
                            if (keyChannel.isConnectionPending()) {
                                keyChannel.finishConnect();
                            }
                            String request = "GET " + file + " \r\n\r\n";
                            keyChannel.write(encoder.encode(CharBuffer.wrap(request)));
                        } else if (key.isReadable()) {
                            keyChannel.read(buffer);
                            buffer.flip();

                            decoder.decode(buffer, charBuffer, false);
                            charBuffer.flip();
                            System.out.print(charBuffer);

                            buffer.clear();
                            charBuffer.clear();

                        } else {
                            System.err.println("Unknown key");
                        }
                    }
                } catch (ConcurrentModificationException e) {
                }
            }
        } catch (UnknownHostException e) {
            System.err.println(e);
        } catch (IOException e) {
            System.err.println(e);
        } finally {
            if (channel != null) {
                try {
                    channel.close();
                } catch (IOException ignored) {
                }
            }
        }
        System.out.println("\nDone.");
    }
}