说明

HttpServer:容器服务入口,监听一个端口
Request:对请求报文做处理,获取http请求报文第一行的资源路径
Response:延续 探究一 的内容
Servlet:自定义servlet
ServletProcessor:请求servlet资源的处理
TestControllerServlet:模拟测试类，实现servlet接口

代码

HttpServer

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

public class HttpServer {
	//静态资源的路径
	public  static final String WEB_ROOT = "D:\\tomcat_servlet\\static";
	//关闭命令
	private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";
	//是否关闭socket
	private boolean shutdown = false;
	
	public static void main(String[] args) {
		HttpServer server = new HttpServer();
		server.await();
	}
	
	public void await() {
		ServerSocket serverSocket = null;
		
		int port = 8080;
		
		try {
			serverSocket = new ServerSocket(port);
		} catch (IOException  e) {
			e.printStackTrace();
		}
		
		while(!shutdown) {
			Socket socket = null;
			InputStream in = null;
			OutputStream out = null;
			
			try {
				socket = serverSocket.accept();
				in = socket.getInputStream();
				out = socket.getOutputStream();
				
				Request request = new Request(in);
				request.parse();
				
				
				
				if(request.getUri() == null ) {
					socket.close();
					continue;
				}
				
				Response response = new Response(out, request);
				
				if(request.getUri().startsWith("/servlet/")) {
					//处理servlet
					new ServletProcessor().process(request, response);
				}else {
					//静态资源
					response.sendStaticResource();
				}
				
				socket.close();
				
				shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
				
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}
}

Request

import java.io.InputStream;

public class Request {
	private InputStream in;
	private String uri = null;
	private static final int BUFFER_SIZE = 2048;
	
	public Request (InputStream in){
		this.in = in;
	}
	
	public void parse() {
		StringBuffer request = new StringBuffer(BUFFER_SIZE);
		
		int i = 0;
		byte[] buffer = new byte[BUFFER_SIZE];
		
		try {
			i = in.read(buffer);
		} catch (Exception e) {
			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());
	}
	
	
	private String parseUri(String requestString) {
		int index1,index2;
		index1 = requestString.indexOf(' ');
		if(index1 != -1 ) {
			index2 = requestString.indexOf(' ',index1 + 1);
			if(index2 > index1) {
				return requestString.substring(index1 + 1, index2);
			}
		}
		
		return null;
	}
	
	public String getUri() {
		return uri;
	}
}

Response

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

public class Response {
	
	private static final int BUFFER_SIZE = 1024;
			
	Request request;
	
	OutputStream out;
	
	public Response(OutputStream out,Request request) {
		this.out = out;
		this.request = request;
	}
	
	public void sendStaticResource() {
		byte[] bytes = new byte[BUFFER_SIZE];
		
		FileInputStream fin = null;
		
		try {
			File file = new File(HttpServer.WEB_ROOT + File.separator + request.getUri());
			if(file.exists()) {
				fin = new FileInputStream(file);
				String pre = "HTTP/1.1 200 ok\r\n\r\n" ;
				out.write(pre.getBytes());
				int ch = fin.read(bytes, 0, BUFFER_SIZE);
				while(ch != -1) {
					out.write(bytes,0,ch);
					ch = fin.read(bytes, 0, BUFFER_SIZE);
				}
				out.flush();
			}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"
						+"
File Not Found
";
				
				out.write(errorMessage.getBytes());
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			if(fin != null) {
				try {
					fin.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
	}
}

Servlet

public interface Servlet {

	public void init();
	
	public void service(Request request,Response response);
	
	public void destroy();
	
}

ServletProcessor

import java.io.File;
import java.net.URL;
import java.net.URLClassLoader;

public class ServletProcessor {
	
	public void process(Request request,Response response) {
		String uri = request.getUri();
		
		String servletName = uri.substring(uri.lastIndexOf("/")+1);
		
		ClassLoader loader = null;
		
		try {
			URL[] urls = new URL[1];
			File classPath = new File(System.getProperty("user.dir"));
			classPath = new File("D:java\\mytomcat\\classes\\");
			URL classUri = classPath.toURL();
			urls[0] = classUri;
			loader = new URLClassLoader(urls);
//			loader = this.getClass().getClassLoader();
		} catch (Exception e) {
			e.printStackTrace();
		}
		
		Class myClass = null;
		
		try {
			/**
			* TestControllerServlet包名是serveletserver --暂时先这样
			*/
			myClass = loader.loadClass("serveletserver."+servletName);
	    }catch (Exception e) {
			e.printStackTrace();
		}
		
		Servlet servlet = null;
		try {
			servlet = (Servlet) myClass.newInstance();
			
			servlet.service(request, response);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

TestControllerServlet

在同一个包还可以创建其他类似的类

import java.io.IOException;

public class TestControllerServlet implements Servlet{

	@Override
	public void init() {
	}


	@Override
	public void destroy() {
	}

	@Override
	public void service(Request request, Response response) {
		String message = "HTTP/1.1 200 ok\r\n\r\nhello";
		try {
			response.out.write(message.getBytes());
			response.out.flush();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

请求测试

http://localhost:8080/servlet/TestControllerServlet