tomcat学习(一)----HTTP服务器是怎么工作的(一个简单的tomcat)

1.Request类(模拟HttpServletRequest)

package ex01.pyrmont;

import java.io.IOException;
import java.io.InputStream;

public class Request {
	private InputStream input;
	private String uri;
	
	public Request(InputStream input) {
		this.input = input;
	}
	public String getUri() {
		return uri;
	}
	
	/**
	 * 读取InputStream中内容，转化成字符串，调用解析字符串方法解析
	 */
	public void parse() {
		//从socket中读取字符
		StringBuffer request = new StringBuffer(2048);
		int i;
		byte[] buffer = new byte[2048];
		try {
			i = input.read(buffer);
		} catch (IOException e) {
			e.printStackTrace();
			i = -1;
		}
		
		for(int j=0; j<i; j++) {
			request.append((char)buffer[j]);
		}
		System.out.println("HTTP Request:");
		System.out.print(request.toString());
		uri = parseURI(request.toString());
	}
	
	/**
	 *截取requestString第一个空格和第二个空格之间的内容返回 
	 */
	private String parseURI(String requestString) {
		int index1;
		int index2;
		index1 = requestString.indexOf(' ');
		if(index1 != -1) {
			index2 = requestString.indexOf(' ', index1 + 1);
			if (index2 > index1) {
				return requestString.substring(index1 + 1, index2);
			}
		}
		return "";
	}
}

2.Response类(模拟HttpServletResponse)

package ex01.pyrmont;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 *HTTP Response =
 *   状态行 Status-Line=HTTP-Version SP Status-Code SP Reason-Phrase CRLF
 *   响应头部字段 ((general-header | response-header | entity-header) CRLF)
 *   空行 CRLF
 *   响应主体 message-body
 */
public class Response {
	private static final int BUFFER_SIZE = 1024;
	Request request;
	OutputStream output;
	public Response(OutputStream output) {
		this.output = output;
	}
	public void setRequset(Request request) {
		this.request = request;
	}
	public void sendStaticResource() {
		byte[] bytes = new byte[BUFFER_SIZE];
		FileInputStream fis = null;
		try {
			File file = new File(HttpServer.WEB_ROOT, request.getUri());
			if(file.exists()) {
				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);
				}
			} else {
				//文件不存在
				String errorMessage = "HTTP/1.1 404 File Not Found\r\n"
									+ "Content-Type: text/html\r\n"
									+ "Content-Length: 23\r\n"
									+ "\r\n"
									+ "<h1>File Not Found</h1>";
				output.write(errorMessage.getBytes());
			}
		
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if(fis != null) {
				try {
					fis.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
}

3.HttpServer类(模拟主服务)

package ex01.pyrmont;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;

public class HttpServer {
	/**
	 * WEB_ROOT是html文件和其他文件所存放的目录 System.getProperty("user.dir")获得的是该文件编译后存放的目录
	 * 对于这个包，WEB_ROOT是在工作目录下的"webroot"
	 * 工作目录是在系统中java命令被执行的地方
	 */
	public static final String WEB_ROOT = System.getProperty("user.dir") + File.separator + "webroot";
	// shutdown command
	private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";
	// 判断是否关闭服务器标志
	private boolean shutdown = false;
	
	public void await() {
		ServerSocket server = null;
		int port = 9999;
		try {
			server = new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));
		} catch (IOException e) {
			e.printStackTrace();
			System.exit(1);
		}
		
		//循环等待请求
		while(!shutdown) {
			Socket socket = null;
			InputStream input = null;
			OutputStream output = null;
			
			try {
				socket = server.accept();
				input = socket.getInputStream();
				output = socket.getOutputStream();
				
				//创建一个Requset对象并解析
				Request request = new Request(input);
				request.parse();
				
				//创建一个Response对象来输出内容
				Response response = new Response(output);
				response.setRequset(request);
				response.sendStaticResource();
				
				//关闭socket
				socket.close();
				//检查URI是否是关闭命令
				shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		
	}
	
	public static void main(String[] args) {
		HttpServer server = new HttpServer();
		server.await();
	}
}

4.运行程序
在浏览器输入：localhost:9999/aaa.txt等会返回相应文件，或找不到提示

这三个类实现了一个简单的web服务器是如何工作的