学步园

一直不理解Http协议，觉得很抽象很神秘，看 《how tomcat work》时看到搭建了一个简单的http服务器，发现协议其实就是对消息格式的规范，就是大家都按这个规范约定的格式发消息收消息。

1.建立sockerserver服务

ServerSocket serverSocket = null;<br /> int port = 8088;<br /> try {<br /> serverSocket = new ServerSocket(port, 1, InetAddress<br /> .getByName("127.0.0.1"));<br /> log.info("服务启动");<br /> } catch (IOException e) {<br /> e.printStackTrace();<br /> System.exit(1);<br /> }

2.监听相应端口

socket = serverSocket.accept();<br /> input = socket.getInputStream();<br /> output = socket.getOutputStream();<br />

3.对监听到的字节进行解析

// create Request object and parse<br /> Request request = new Request(input);<br /> request.parse();

Request 实际上就是解析HTTP协议并得到资源的请求路径uri。

public void parse() {<br /> // Read a set of characters from the socket<br /> StringBuffer request = new StringBuffer(2048);<br /> int i;<br /> byte[] buffer = new byte[2048];<br /> try {<br /> i = input.read(buffer);<br /> } catch (IOException e) {<br /> e.printStackTrace();<br /> i = -1;<br /> }<br /> for (int j = 0; j < i; j++) {<br /> request.append((char) buffer[j]);<br /> }<br /> log.info("request head /n"+request.toString());<br /> uri = parseUri(request.toString());<br /> }</p> <p> private String parseUri(String requestString) {<br /> int index1, index2;<br /> index1 = requestString.indexOf(' ');<br /> if (index1 != -1) {<br /> index2 = requestString.indexOf(' ', index1 + 1);<br /> if (index2 > index1)<br /> return requestString.substring(index1 + 1, index2);<br /> }<br /> return null;<br /> }

4.对请求进行响应

// create Response object<br /> Response response = new Response(output);<br /> response.setRequest(request);<br /> response.sendStaticResource();

这里实际上根据request分析的uri进行资源的字节化，输出到socket的out

public void sendStaticResource() throws IOException {<br /> byte[] bytes = new byte[BUFFER_SIZE];<br /> FileInputStream fis = null;<br /> try {<br /> File file = new File(HttpServer.WEB_ROOT, request.getUri());<br /> if (file.exists()) {<br /> fis = new FileInputStream(file);<br /> int ch = fis.read(bytes, 0, BUFFER_SIZE);<br /> while (ch != -1) {<br /> output.write(bytes, 0, ch);<br /> ch = fis.read(bytes, 0, BUFFER_SIZE);<br /> }<br /> } else {<br /> // file not found<br /> String errorMessage = "HTTP/1.1 404 File Not Found/r/n"<br /> + "Content-Type: text/html/r/n"<br /> + "Content-Length: 23/r/n" + "/r/n" +</p> <p> "<h1>File Not Found</h1>";<br /> output.write(errorMessage.getBytes());<br /> }<br /> } catch (Exception e) {<br /> // thrown if cannot instantiate a File object<br /> System.out.println(e.toString());<br /> } finally {<br /> if (fis != null)<br /> fis.close();<br /> }<br /> }

可以看到其实就是简单的将资源用字节流输出。

最后提供完整的代码包（http://download.csdn.net/source/3194644），运行HttpServer.java 后可以通过浏览器访问：http://localhost:8088/index.htm 可以看到静态页面，通过后台可以看到请求的Http信息。