Tomcat ：一个简单的Servlet容器

圣凤凌霜

　　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。