Tomcat ：一个简单的Servlet容器

Servlet容器处理Servlet请求的简单流程图如下图所示：

 

 UML类图如下图所示：

 

HttpServletProcessor类：

 

package com.flyer.tomcat.first;

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;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 一个简单的http服务器
 * <p />
 * 
 * @author Administrator
 */
public class HttpServer {
    
    private static Logger logger = LoggerFactory.getLogger(HttpServer.class);

    private final static String SHUTDOWN_COMMAND = "/shutdown";
    
    public final static String WEB_ROOT = System.getProperty("user.dir") + File.separator + "webroot";

    private boolean shutdown = false;

    public static void main(String[] args) {
        logger.info("server start");
        HttpServer server = new HttpServer();
        try {
            server.await();
        } catch (IOException e) {
            logger.error("io exception",e);
        }
    }

    private void await() throws IOException {

        ServerSocket serverSocket = new ServerSocket(9090,1,InetAddress.getByName("127.0.0.1"));
        InputStream input = null;
        OutputStream output = null;
        while (!shutdown) {
            Socket socket = null;
            try {
                socket = serverSocket.accept();
                input = socket.getInputStream();
                output = socket.getOutputStream();
                Request request = new Request(input);
                request.parse();
                Response response = new Response(output);
                response.setRequest(request);
                
                if(request.getUri().startsWith("/servlet")){
                    ServletProcessor servletProcessor = new ServletProcessor();
                    servletProcessor.process(request, response);
                }else{
                    StaticResourceProcessor processor = new StaticResourceProcessor();
                    processor.process(request, response);
                }
                
                
                socket.close();

                shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                
                input.close();
                output.close();
            }
        }

    }

}

 

代码

 

package com.flyer.tomcat.first;

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

import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Servlet请求处理器
 * <p />
 * 
 * @author Administrator
 */
public class ServletProcessor implements Processor {

    private static Logger logger = LoggerFactory.getLogger(ServletProcessor.class);

    // private final static String FILE_PATH = Constants.getClassPath() + File.separator + "com" +
    // File.separator
    // + "flyer" + File.separator + "tomcat" + File.separator + "first" + "" + File.separator;

    @Override
    public void process(HttpServletRequest request, HttpServletResponse response) {
        Request internalRequest = (Request) request;
        String uri = internalRequest.getUri();
        String servletClassName = uri.substring(uri.lastIndexOf("/") + 1);
        URLClassLoader classLoader = null;
        File file = new File(Constants.getClassPath());
        URL url = null;
        try {
            url = file.toURI().toURL();
        } catch (MalformedURLException e) {
            logger.error("convert to url error", e);
        }
        logger.info("url:" + url);
        URL[] urls = new URL[1];
        urls[0] = url;
        classLoader = new URLClassLoader(urls);
        Class<?> myClass = null;
        try {
            myClass = classLoader.loadClass(servletClassName);
        } catch (ClassNotFoundException e) {
            logger.error("class not found", e);
        }
        Servlet servlet = null;
        if (myClass != null) {
            try {
                servlet = (Servlet) myClass.newInstance();
            } catch (InstantiationException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                servlet.service(request, response);
            } catch (ServletException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

    }

}

 

改进：

 

添加facade类，为的是Request类中的parse方法和getUri方法不被Servlet类访问。