浅析Tomcat(一)

wzh789

想必大家都知道Tomcat其实就是servlet容器。负责servlet前期的准备工作。在这里简单用代码模拟一下Tomcat的工作。
首先牵涉到网络，那么网络编程是少不了的。
1.这个类就是一个servlet服务的工具，程序从这里开始
package com.arz.server;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class ServletServer {
private ServerSocket serverSocket;
private int port;
private boolean shutDown;
public ServletServer (int port){
this.port = port;
}
public void startServer(){
try{
serverSocket = new ServerSocket(port);
}catch(IOException e){
System.out.println("监听"+port+"失败！");
System.exit(0);
}
while(!shutDown){
try{
//监听着8080端口
Socket socket = serverSocket.accept();
//实例一个Runnable接口类，在这里面运行全部的核心工作
DispatchSocket dispatchSocket = new DispatchSocket(socket);
//启动Runnable中的run()方法
new Thread(dispatchSocket).start();
}catch(IOException e){
System.out.println("客户端出了问题");
e.printStackTrace();
}
}
}
public static void main(String[] args){
ServletServer server = new ServletServer(8080);
server.startServer();
}
public boolean isShutDown(){
return shutDown;
}
public void setShutDown(boolean shutDown){
this.shutDown = shutDown;
}
}

2.创建DispatchSocket这个类是为了满足Tomcat的多线程而产生的。有了这个类“Tomcat”就可以同时被多个访问了
package com.arz.server;
import java.io.IOException;
import java.net.Socket;
import com.arz.servlet.Servlet;
import com.arz.servlet.ServletMapping;
import com.arz.servlet.TestServlet;
import com.arz.servlet.WebApp;
public class DispatchSocket implements Runnable {
private Socket socket;
public DispatchSocket(Socket socket){
this.socket = socket;
}
@Override
public void run() {
try{
System.out.println("客户端是："+socket.getRemoteSocketAddress());
//实例request，可以跟踪查看Request类，将socket类的输入流交给request。可以看做是HttpServletRequest
Request request = new Request(socket.getInputStream(),8080);
//实例response，可以跟踪查看Response类，将socket类的输出流交给response。结果将会输出到网页。可以看做是HttpServletResponse
Response response = new Response(socket.getOutputStream());
//*****************这里是直接运行Servlet类的service方法*****************
//将这个类看做是HttpServlet
Servlet servlet = new TestServlet();
//调用我们写的service()方法
servlet.service(request, response);
//*****************这里是我们解析web.xml得到的servlet对象,和上面是并行的*****************
//解析web.xml的类，并且将对象的对应关系包装好
WebApp webApp = WebApp.getWebApp();
String urlPattern = request.getUrlPattern();
ServletMapping mapping = webApp.getServletMappings().get(urlPattern);
if(mapping != null){
String servletName = mapping.getServletName();
Servlet servlet1 = webApp.getServletContext().getServlet(servletName);
if(servlet1 != null){
servlet1.service(request, response);
}else{
response.println("没有获得Servlet");
}
}else{
response.print("你请求的url错误，该url不正确。没有找到相应的页面！");
}
}catch(Exception e){
e.printStackTrace();
}finally{
closeSocket(socket);
}
}
public void closeSocket(Socket socket){
if(socket != null){
try{
socket.getOutputStream().flush();
socket.close();
}catch(IOException e){
e.printStackTrace();
}
}
}
}

3.大家应该知道java在servlet编程中只是提供了类的接口，具体的实现是交给服务商完成的。作为比较优秀的服务器Tomcat自然也要实现java定义的servlet类例如HttpServletRequest，下面是HttpServletRequest的模拟代码。当然真正的HttpServletRequest要复杂的多的多
package com.arz.server;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;
public class Request {
private int port;
private String host;
private String urlPattern;
private Map<String,String> map = new HashMap<String,String>();
private String method;
private String headInfo;
private InputStream inStream;
protected Request(InputStream inStream,int port) {
this.inStream = inStream;
this.port = port;
parseRequestHead();
}
private void parseRequestHead(){
byte[] buf = new byte[1024];
try{
inStream.read(buf);
headInfo = new String(buf);
System.out.println(headInfo);
method = headInfo.substring(0,headInfo.indexOf("/")).trim();
System.out.println("请求方式："+method);
host = headInfo.substring(headInfo.indexOf("Host:")+5,headInfo.indexOf(":"+port)).trim();
System.out.println("请求地址："+host);
//??
if(method.equalsIgnoreCase("get")){
parseGetString();
}else if (method.equalsIgnoreCase("post")){
parsePostString();
}
}catch(IOException e){
e.printStackTrace();
}
}
private void parsePostString(){
urlPattern = headInfo.substring(5, headInfo.indexOf("HTTP/")).trim();
String dataString = headInfo.substring(headInfo.lastIndexOf("\r\n")).trim();
//??
StringTokenizer st = new StringTokenizer(dataString,"&");
while(st.hasMoreTokens()){
String[] ss = st.nextToken().split("=");
map.put(ss[0], ss[1]);
}
}
private void parseGetString(){
String url = headInfo.substring(4, headInfo.indexOf("HTTP/"));
if(url.indexOf("?")==-1){
urlPattern = url.trim();
}else{
urlPattern = url.substring(0, url.indexOf("?")).trim();
String dataString = url.substring(url.indexOf("?")+1).trim();
StringTokenizer st = new StringTokenizer(dataString,"&");
while(st.hasMoreTokens()){
String[] ss = st.nextToken().split("=");
map.put(ss[0], ss[1]);
}
}
}
public int getPort() {
return port;
}
public void setPort(int port) {
this.port = port;
}
public String getHost() {
return host;
}
public void setHost(String host) {
this.host = host;
}
public String getUrlPattern() {
return urlPattern;
}
public void setUrlPattern(String urlPattern) {
this.urlPattern = urlPattern;
}
public String getMethod() {
return method;
}
public void setMethod(String method) {
this.method = method;
}
public String getHeadInfo() {
return headInfo;
}
public void setHeadInfo(String headInfo) {
this.headInfo = headInfo;
}
public String getParameter(String name){
if(map != null && map.size() > 0){
return (String)map.get(name);
}
return null;
}
}