基于NIO实现客户端通过HTTP协议访问WEB站点

答案：这只是一个简单的示例，如果你想了解HTTP的详细内容可参考我的一个开源项目JQuickDown

/*
 * Created on 2005-2-1
 *
 * CopyRight by lxleaves_zhang
 */
package test;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.channels.spi.SelectorProvider;
import java.util.Iterator;

public class NIOTest {
    public static SocketChannel createSocketChannel(String host, int port)
            throws IOException {
        SocketChannel sc = SocketChannel
                .open(new InetSocketAddress(host, port));
        sc.configureBlocking(false);
        return sc;
    }

    public static final String host = "www.163.com";

    public static final String path = "/";

    public static final int port = 80;

    public static final byte[] req = ("GET " + path + " HTTP/1.0\r\nHost:"
            + host + "\r\n\r\n").getBytes();

    public static void main(String[] args) {
        Selector sel = null;
        ByteBuffer buf = ByteBuffer.allocate(256);
        SocketChannel sc[] = new SocketChannel[2];
        try {
            sel = SelectorProvider.provider().openSelector();
            sc[0] = createSocketChannel(host, port);
            sc[1] = createSocketChannel(host, port);
            buf.put(req);
            buf.flip();
            sc[0].write(buf);
            buf.flip();
            sc[1].write(buf);
            sc[0].register(sel, sc[0].validOps());
            sc[1].register(sel, sc[1].validOps());
        } catch (IOException e) {
            e.printStackTrace();
        }
        while (sel.isOpen()) {
            try {
                sel.select();
            } catch (IOException e) {
                e.printStackTrace();
            }
            Iterator it = sel.selectedKeys().iterator();
            while (it.hasNext()) {
                SelectionKey sk = (SelectionKey) it.next();
                it.remove();
                SocketChannel next = (SocketChannel) sk.channel();
                buf.clear();
                try {
                    // check whether finish
                    if (next.read(buf) == -1) {
                        sk.cancel();
                        next.close();

                        if (!it.hasNext()) {
                            sel.close();
                        }
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
                buf.flip();
                if (buf.limit() == 0)
                    continue;
                byte b[] = new byte[buf.limit()];
                buf.get(b);
                // System.out.println(next == sc[0]);
                if (next == sc[0])
                    System.out.print(new String(b));
                else
                    System.err.print(new String(b));
            }
        }
    }
}

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