how tomcat works<二>

上一篇博客《自己动手编写tomcat服务器(一)》并不完美，它只能支持请求静态文件，如hello.html,不能请求servlet文件，这篇将完善，同时支持这两种请求

应用包含以下文件：

HttpServer1

Request

Response

StaticResourceProcessor

ServletProcessor1

Constants

UML类图如下：



应用的入口是HttpServer1的main方法，它创建了一个HttpServer1的实例并调用它的await方法，这个方法等待HTTP请求，为每一个请求创建Request

对象和Response对象，然后根据请求的是静态文件还是一个servlet，把它们传给StaticResourceProcessor或ServletProcessor1的实例

如果请求的是静态文件，其路径为：http://machineName:port/staticResource

如果请求的是servlet，路径为：http://machineName:port/servlet/servletClass

HttpServer1的源码如下：

[java] view
plaincopy

package ex02.pyrmont;

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 HttpServer1 {

private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";

private boolean shutdown = false;

public static void main(String[] args) {

HttpServer1 server = new HttpServer1();

server.await();

}

private void await() {

ServerSocket serverSocket = null;

int port = 8080;

try{

serverSocket = new ServerSocket(port,1,InetAddress.getByName("127.0.0.1"));

}catch(IOException e){

e.printStackTrace();

System.exit(1);

}

while(!shutdown){

Socket socket = null;

InputStream input = null;

OutputStream output = 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/")){

ServletProcessor1 processor = new ServletProcessor1();

processor.process(request,response);

}else{

StaticResourceProcessor processor = new StaticResourceProcessor();

processor.process(request,response);

}

socket.close();

shutdown = request.getUri().equals(SHUTDOWN_COMMAND);

}catch(IOException e){

e.printStackTrace();

System.exit(1);

}

}

}

}

Request类的源代码如下：

[java] view
plaincopy

package ex02.pyrmont;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStream;

import java.io.UnsupportedEncodingException;

import java.util.Enumeration;

import java.util.Locale;

import java.util.Map;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletInputStream;

import javax.servlet.ServletRequest;

public class Request implements ServletRequest{

private InputStream input;

private String uri;

public Request(InputStream input) {

this.input = input;

}

public void parse() {

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(request.toString());

uri = parseUri(request.toString());

}

public String getUri() {

return uri;

}

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 Object getAttribute(String arg0) {

// TODO Auto-generated method stub

return null;

}

public Enumeration getAttributeNames() {

// TODO Auto-generated method stub

return null;

}

public String getCharacterEncoding() {

// TODO Auto-generated method stub

return null;

}

public int getContentLength() {

// TODO Auto-generated method stub

return 0;

}

public String getContentType() {

// TODO Auto-generated method stub

return null;

}

public ServletInputStream getInputStream() throws IOException {

// TODO Auto-generated method stub

return null;

}

public String getLocalAddr() {

// TODO Auto-generated method stub

return null;

}

public String getLocalName() {

// TODO Auto-generated method stub

return null;

}

public int getLocalPort() {

// TODO Auto-generated method stub

return 0;

}

public Locale getLocale() {

// TODO Auto-generated method stub

return null;

}

public Enumeration getLocales() {

// TODO Auto-generated method stub

return null;

}

public String getParameter(String arg0) {

// TODO Auto-generated method stub

return null;

}

public Map getParameterMap() {

// TODO Auto-generated method stub

return null;

}

public Enumeration getParameterNames() {

// TODO Auto-generated method stub

return null;

}

public String[] getParameterValues(String arg0) {

// TODO Auto-generated method stub

return null;

}

public String getProtocol() {

// TODO Auto-generated method stub

return null;

}

public BufferedReader getReader() throws IOException {

// TODO Auto-generated method stub

return null;

}

public String getRealPath(String arg0) {

// TODO Auto-generated method stub

return null;

}

public String getRemoteAddr() {

// TODO Auto-generated method stub

return null;

}

public String getRemoteHost() {

// TODO Auto-generated method stub

return null;

}

public int getRemotePort() {

// TODO Auto-generated method stub

return 0;

}

public RequestDispatcher getRequestDispatcher(String arg0) {

// TODO Auto-generated method stub

return null;

}

public String getScheme() {

// TODO Auto-generated method stub

return null;

}

public String getServerName() {

// TODO Auto-generated method stub

return null;

}

public int getServerPort() {

// TODO Auto-generated method stub

return 0;

}

public boolean isSecure() {

// TODO Auto-generated method stub

return false;

}

public void removeAttribute(String arg0) {

// TODO Auto-generated method stub

}

public void setAttribute(String arg0, Object arg1) {

// TODO Auto-generated method stub

}

public void setCharacterEncoding(String arg0)

throws UnsupportedEncodingException {

// TODO Auto-generated method stub

}

}

Request类代表传递给Servlet的service方法的request对象，它实现了javax.servlet.ServletRequest接口

Response类的源代码如下：

[java] view
plaincopy

package ex02.pyrmont;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.OutputStream;

import java.io.PrintWriter;

import java.util.Locale;

import javax.servlet.ServletOutputStream;

import javax.servlet.ServletResponse;

public class Response implements ServletResponse{

private static final int BUFFER_SIZE = 1024;

private OutputStream output;

private Request request;

private PrintWriter writer;

public Response(OutputStream output) {

this.output = output;

}

public void setRequest(Request request) {

this.request = request;

}

public void sendStaticResource() throws IOException {

byte[] bytes = new byte[BUFFER_SIZE];

FileInputStream fis = null;

try {

/* request.getUri has been replaced by request.getRequestURI */

File file = new File(Constants.WEB_ROOT, request.getUri());

fis = new FileInputStream(file);

/*

* HTTP Response = Status-Line(( general-header | response-header |

* entity-header ) CRLF) CRLF [ message-body ] Status-Line =

* HTTP-Version SP Status-Code SP Reason-Phrase CRLF

*/

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) {

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());

} finally {

if (fis != null)

fis.close();

}

}

public void flushBuffer() throws IOException {

// TODO Auto-generated method stub

}

public int getBufferSize() {

// TODO Auto-generated method stub

return 0;

}

public String getCharacterEncoding() {

// TODO Auto-generated method stub

return null;

}

public String getContentType() {

// TODO Auto-generated method stub

return null;

}

public Locale getLocale() {

// TODO Auto-generated method stub

return null;

}

public ServletOutputStream getOutputStream() throws IOException {

// TODO Auto-generated method stub

return null;

}

public PrintWriter getWriter() throws IOException {

writer = new PrintWriter(output,true);

return writer;

}

public boolean isCommitted() {

// TODO Auto-generated method stub

return false;

}

public void reset() {

// TODO Auto-generated method stub

}

public void resetBuffer() {

// TODO Auto-generated method stub

}

public void setBufferSize(int arg0) {

// TODO Auto-generated method stub

}

public void setCharacterEncoding(String arg0) {

// TODO Auto-generated method stub

}

public void setContentLength(int arg0) {

// TODO Auto-generated method stub

}

public void setContentType(String arg0) {

// TODO Auto-generated method stub

}

public void setLocale(Locale arg0) {

// TODO Auto-generated method stub

}

}

它实现了javax.servlet.ServletResponse接口，代表传递给servlet的service方法的response对象

StaticResourceProcessor的源代码如下：

[java] view
plaincopy

package ex02.pyrmont;

import java.io.IOException;

public class StaticResourceProcessor {

public void process(Request request, Response response) {

try{

response.sendStaticResource();

}catch(IOException e){

e.printStackTrace();

}

}

}

它用来处理对静态资源的请求

ServletProcessor1的源码如下：

[java] view
plaincopy

package ex02.pyrmont;

import java.io.File;

import java.io.IOException;

import java.net.URL;

import java.net.URLClassLoader;

import java.net.URLStreamHandler;

import javax.servlet.Servlet;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

public class ServletProcessor1 {

public void process(Request request, Response response) {

String uri = request.getUri();

String servletName = uri.substring(uri.lastIndexOf("/") + 1);

URLClassLoader loader = null;

try{

URL[] urls = new URL[1];

URLStreamHandler streamHandler = null;

File classPath = new File(Constants.WEB_ROOT);

String repository = new URL("file",null,classPath.getCanonicalPath()+ File.separator).toString();

urls[0] = new URL(null,repository,streamHandler);

loader = new URLClassLoader(urls);

}catch(IOException e){

System.out.println(e.toString());

}

Class myClass = null;

try{

myClass = loader.loadClass(servletName);

}catch(ClassNotFoundException e){

System.out.println(e.toString());

}

Servlet servlet = null;

try{

servlet = (Servlet) myClass.newInstance();

servlet.service((ServletRequest)request, (ServletResponse)response);

}catch(Exception e){

System.out.println(e.toString());

}catch(Throwable e){

System.out.println(e.toString());

}

}

}

它用来处理对servlet的请求

Constants的源代码如下：

[java] view
plaincopy

package ex02.pyrmont;

import java.io.File;

public class Constants {

public static final String WEB_ROOT =

System.getProperty("user.dir") + File.separator + "webroot";

}

再写一个简单的servlet测试一下

PrimitiveServlet

[java] view
plaincopy

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.Servlet;

import javax.servlet.ServletConfig;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

public class PrimitiveServlet implements Servlet {

public void destroy() {

System.out.println("destroy");

}

public ServletConfig getServletConfig() {

// TODO Auto-generated method stub

return null;

}

public String getServletInfo() {

// TODO Auto-generated method stub

return null;

}

public void init(ServletConfig arg0) throws ServletException {

System.out.println("init");

}

public void service(ServletRequest arg0, ServletResponse arg1)

throws ServletException, IOException {

System.out.println("form service");

PrintWriter out = arg1.getWriter();

out.println("Hello,roses are red");

out.println("violets are blues");

}

}

将index.html和PrimitiveServlet编译后的class文件放入到webroot目录中，运行HttpServer1程序，在浏览器中输入：http://localhost:8080/index.html

或http://localhost:8080/servlet/PrimitiveServlet，将会看到结果

转自:http://blog.csdn.net/wenjingyu/article/details/10484091