最近自己在学习《how tomcat works》,特意mark一下一些学习心得。
我们知道web服务器是网络应用中不可缺失的一个环节,那么,一个简单的web服务器是怎么实现的呢?
一 HTTP
http请求
一般一个http请求包括以下三个部分:
1 请求方法,如get,post
2 请求头
3 实体
一个http请求的实例如下:
GET /index.jsp HTTP/1.1
Host: localhost:8080
User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:15.0) Gecko/20100101 Firefox/15.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding: gzip, deflate
Connection: keep-alive
注意红色部分的url,这是我们待会要截取出来的。
http响应
与http请求类似,http响应也包括三个部分
1 协议-状态码-描述
2 响应头
3 响应实体段
二 socket类
套接字是网络连接的断点。套接字使得应用程序可以从网络中读取数据,可以向网络中写入数据。不同计算机上的应用程序可以通过套接字发送或接受字节流。java中提供了Socket类来实现这个功能,通过getInputStream和getOutputStream可以获取网络中的输入输出流。
但是,光靠Socket类还是不能够实现我们构建一个服务器应用程序的功能的,因为服务器必须时刻待命,因此java里面提供了ServerSocket类来处理等待来自客户端的请求,当ServerSocket接受到了来自客户端的请求之后,它就会创建一个实例来处理与客户端的通信。
三 服务器应用程序的实现
首先,我们要构建一个封装请求信息的类requst,一个响应请求的类response,还要有一个主程序httpServer来处理客户端来的请求。
- package com.lwq;
- import java.io.IOException;
- import java.io.InputStream;
- /**
- * @author thomaslwq
- * @version 创建时间:Sep 5, 2012 9:59:32 PM
- * 类说明
- * 将浏览器发来的请求信息转化成字符和截取url
- */
- public class Request {
-
- //输入流
- private InputStream input;
- //截取url,如 ,截取部分为 /index.html
- private String uri;
- public Request(InputStream inputStream){
- this.input = inputStream;
- }
-
- public InputStream getInput() {
- return input;
- }
- public void setInput(InputStream input) {
- this.input = input;
- }
- public String getUri() {
- return uri;
- }
- public void setUri(String uri) {
- this.uri = uri;
- }
-
- //从套接字中读取字符信息
- public void parse(){
-
- StringBuffer request = new StringBuffer(2048);
- int i = 0;
- byte[] buffer = new byte[2048];
-
- try {
- i = input.read(buffer);
- } catch (IOException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- i = -1;
- }
- for(int j = 0;j<i;j++){
- request.append((char)(buffer[j]));
- }
- System.out.println(request.toString());
- uri = parseUri(request.toString());
- }
- //截取请求的url
- private String parseUri(String requestString){
-
- int index1 = 0;
- int index2 = 0;
- index1 = requestString.indexOf(' ');
- if(index1!=-1){
- index2 = requestString.indexOf(' ',index1+1);
- if(index2>index1){
- return requestString.substring(index1+1,index2);
- }
- }
-
- return null;
- }
-
-
-
-
- }
下面是封装了响应请求的类response
- package com.lwq;
- import java.io.File;
- import java.io.FileInputStream;
- import java.io.FileNotFoundException;
- import java.io.IOException;
- import java.io.OutputStream;
- import java.io.PrintWriter;
- /**
- * @author thomaslwq
- * @version 创建时间:Sep 5, 2012 9:59:53 PM
- * 类说明 根据相应信息返回结果
- */
- public class Response {
-
- private static final int BUFFER_SIZE = 1024;
- Request request;
- OutputStream output;
- public Response(OutputStream output){
- this.output = output;
- }
-
- public void sendStaticResource() throws IOException{
-
- byte[] bytes = new byte[BUFFER_SIZE];
- FileInputStream fis = null;
-
- File file = new File(HttpServer.WEB_ROOT,request.getUri());
- if(file.exists()){
- try {
- fis = new FileInputStream(file);
- int ch = fis.read(bytes,0,BUFFER_SIZE);
- while(ch != -1){
- output.write(bytes,0,ch);
- ch = fis.read(bytes,0,BUFFER_SIZE);
- }
-
- } catch (FileNotFoundException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }catch(IOException e){
- e.printStackTrace();
- }finally{
- if(fis !=null){
- fis.close();
- }
- }
-
- }else{
- //找不到文件
- String errorMessage = "HTTP/1.1 404 File Not Found\r\n" +
- "Content-Type: text/html\r\n" +
- "Content-Length: 23\r\n" +
- "\r\n" +
- "
File Not Found
";
- try {
- output.write(errorMessage.getBytes());
- output.flush();
- } catch (IOException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- }
- }
- public Request getRequest() {
- return request;
- }
- public void setRequest(Request request) {
- this.request = request;
- }
- public OutputStream getOutput() {
- return output;
- }
- public void setOutput(OutputStream output) {
- this.output = output;
- }
- public static int getBUFFER_SIZE() {
- return BUFFER_SIZE;
- }
-
-
- }
接下来是主程序,
- package com.lwq;
- import java.io.File;
- import java.io.InputStream;
- import java.io.OutputStream;
- import java.net.InetAddress;
- import java.net.ServerSocket;
- import java.net.Socket;
- /**
- * @author thomaslwq
- * @version 创建时间:Sep 5, 2012 9:59:16 PM
- * 类说明
- */
- public class HttpServer {
- /**
- * @param args
- */
-
- //WEB_ROOT是服务器的根目录
- public static final String WEB_ROOT = System.getProperty("user.dir")+File.separator+"webroot";
-
- //关闭的命令
- private static final String SHUTDOWN_COMMAND= "/SHUTDOWN";
-
- public static void main(String[] args) {
- // TODO Auto-generated method stub
- HttpServer server = new HttpServer();
- server.await();
- }
- public void await(){
- ServerSocket serverSocket = null;
- int port = 8080;
- try {
- serverSocket = new ServerSocket(port,1,InetAddress.getByName("127.0.0.1"));
- while(true)
- {
- try {
- Socket socket = null;
- InputStream input = null;
- OutputStream output = null;
- socket = serverSocket.accept();
- input = socket.getInputStream();
- output = socket.getOutputStream();
- //封装request请求
- Request request = new Request(input);
- request.parse();
- //封装response对象
- Response response = new Response(output);
- response.setRequest(request);
- response.sendStaticResource();
- socket.close();
- } catch (Exception e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- continue;
- }
-
- }
- } catch (Exception e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
-
-
-
- }
-
- }
运行httpServer,在浏览器中打下就能看到服务器响应的结果了。
附带工程源码
SimpleWebServer.rar
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