平时在使用tomcat、jetty时，只是使用里面的servlet、filter等，从来没想过它们如何同浏览器进行交互的。工作中遇到一些问题，在同其它同事交流及学习源码的过程中，才明白底层原来走的也是socket，才知道所谓的NIO是什么。。。
了解NIO之前，肯定得先了解BIO，出于学习的目的 ，使用BIO写一个简单的http服务器DEMO：浏览器输入任何请求，后台打印出请求信息并在浏览器中输出Hello World
1 import java.io.BufferedReader; 2 import java.io.BufferedWriter; 3 import java.io.IOException; 4 import java.io.InputStream; 5 import java.io.InputStreamReader; 6 import java.io.OutputStream; 7 import java.io.OutputStreamWriter; 8 import java.net.InetSocketAddress; 9 import java.net.ServerSocket;10 import java.net.Socket;11 12 public class BioServer {13 ????private ServerSocket serverSocket;14 ????15 ????private String ip;16 ????17 ????private int port;18 ????19 ????public BioServer(String ip, int port) {20 ????????this.ip = ip;21 ????????this.port = port;22 ????}23 ????24 ????public void startListen() throws IOException {25 ????????serverSocket = new ServerSocket();26 ????????serverSocket.bind(new InetSocketAddress(ip, port)); //创建对指定端口及IP的监听27 ????????28 ????????while (true) {29 ????????????accept();30 ????????}31 ????}32 ????33 ????private void accept() throws IOException {34 ????????//收到客户端的请求35 ????????Socket socket = serverSocket.accept();36 ????????37 ????????//输入流用于接收客户端传输过来的数据38 ????????InputStream in = socket.getInputStream();39 ????????InputStreamReader reader = new InputStreamReader(in);40 ????????BufferedReader br = new BufferedReader(reader);41 ????????String line = null;42 ????????while ((line = br.readLine()) != null) {43 ????????????System.out.println(line);44 ????????????//按照HTTP协议，请求头和请求体之间为一空行分隔45 ????????????if ("".equals(line)) {46 ????????????????break;47 ????????????}48 ????????}49 ????????50 ????????//输出流用于向客户端发送响应消息，需遵从HTTP协议格式51 ????????OutputStream out = socket.getOutputStream();52 ????????OutputStreamWriter writer = new OutputStreamWriter(out);53 ????????BufferedWriter bw = new BufferedWriter(writer);54 ????????bw.write("HTTP/1.1 200 OK\n");55 ????????bw.write("Content-Type: text/html; charset=UTF-8\n");56 ????????bw.write("\n");57 ????????bw.write("<html>");58 ????????bw.write("<head>");59 ????????bw.write("<title>");60 ????????bw.write("BIO Http Server");61 ????????bw.write("</title>");62 ????????bw.write("</head>");63 ????????bw.write("<body>");64 ????????bw.write("<h1>Hello World!</h1>");65 ????????bw.write("</body>");66 ????????bw.write("</html>");67 ????????68 ????????//必须在请求读取和响应写入都处理完毕之后才可以调用close方法，将输入流关闭也会导致输出流不可用69 ????????bw.close();70 ????????writer.close();71 ????????out.close();72 ????????br.close();73 ????????reader.close();74 ????????in.close();75 ????????socket.close();76 ????}77 ????78 ????public static void main(String[] args) {79 ????????BioServer server = new BioServer("127.0.0.1", 8080);80 ????????try {81 ????????????server.startListen();82 ????????} catch (IOException e) {83 ????????????e.printStackTrace();84 ????????}85 ????}86 }使用BIO建立简单的http服务器
原文地址：http://www.cnblogs.com/smart-elf/p/7710837.html