手动实现Web容器（转）

一个类似Tomcat的容器，不过只是模拟Web容器的解析过程，只做了简单的解析HTML。
      首先用Java IDE建立一个普通的Java Project，要解析web少不了Request和Response对象，所以在工程（项目）里建立两个类：MyHttpServletRequest（对应HttpServletRequest）、MyHttpServletResponse(对应 HttpServletResponse),如下：

//MyHttpServletRequest.java
package com.kalman03.servlet;

import java.io.BufferedReader;
import java.io.IOException;

public class MyHttpServletRequest{
    private BufferedReader br;
    private String header;
    public MyHttpServletRequest(BufferedReader br){
        try{
            this.br = br;
            this.header = br.readLine();//  GET /index.html HTTP/1.1
        }catch(IOException ex){
            ex.printStackTrace();
        }
    }   

    public String getURL(){
        String [] temp = header.split(" ");
        return temp[1].substring(1);
    }
}

//MyHttpServletResponse.java
package com.kalman03.servlet;

import java.io.PrintWriter;

public class MyHttpServletResponse{
    private PrintWriter out;
    public MyHttpServletResponse(PrintWriter out){
        this.out = out;
        out.println("HTTP/1.1 200 OK");
    }

    public PrintWriter getWriter(){
        return out;
    }
}

构造一个抽象类MyHttpServlet：

//MyHttpServlet.java
package com.kalman03.servlet;

public abstract class MyHttpServlet{
    public abstract void doGet(MyHttpServletRequest request,MyHttpServletResponse response)throws Exception;
    public abstract void doPost(MyHttpServletRequest request,MyHttpServletResponse response)throws Exception;
}

用MyServlet类实现上面MyHttpServlet抽象类：

//MyServlet.java
package com.kalman03.servlet.ext;

import java.io.BufferedReader;
import java.io.PrintWriter;
import java.io.File;
import java.io.FileReader;
import com.kalman03.servlet.MyHttpServlet;
import com.kalman03.servlet.MyHttpServletRequest;
import com.kalman03.servlet.MyHttpServletResponse;

//该类继承MyHttpServlet类，实现其中的doGet(),doPost()方法
public class MyServlet extends MyHttpServlet {
    private PrintWriter out;
    private String url;

    public void doGet(MyHttpServletRequest request,
                      MyHttpServletResponse response) throws Exception {
        this.out = response.getWriter();
        url = request.getURL();
        if (url.equals("")) {
            url = "index.html";
        }
        File file = new File(url);
        FileReader fr = new FileReader(file);
        BufferedReader brR = new BufferedReader(fr);
        String temp;
        while ((temp = brR.readLine()) != null) {
            out.println(temp);
        }
        out.close();
        brR.close();
        fr.close();
    }

    public void doPost(MyHttpServletRequest request,
                       MyHttpServletResponse response) throws Exception {
        this.doGet(request, response);
    }
}

跑一个线程监听类MyWebService：

//MyWebService.java
package com.kalman03.servlet;

import java.net.ServerSocket;
import java.net.Socket;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;

public class MyWebService {
    public MyWebService(MyHttpServlet ms) {
        try {
            ServerSocket ss = new ServerSocket(2008);
            while (true) {
                Socket s = ss.accept();
                new myRunnable(s, ms).start();
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}


//线程监听
class myRunnable extends Thread {
    private Socket s;
    private MyHttpServlet ms;
    public myRunnable(Socket s, MyHttpServlet ms) {
        this.s = s;
        this.ms = ms;
    }

    public void run() {
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader(s.
                    getInputStream()));
            PrintWriter out = new PrintWriter(s.getOutputStream(), true);
            MyHttpServletRequest req = new MyHttpServletRequest(br);
            MyHttpServletResponse rep = new MyHttpServletResponse(out);
            ms.doGet(req, rep);
            br.close();
            out.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}

至此大工基本告成，再来一个main方法（MainClass类）就OK了：

//MainClass.java
package com.kalman03.test;

import com.kalman03.servlet.MyWebService;
import com.kalman03.servlet.ext.MyServlet;

public class MainClass {
    public static void main (String[] args) {
       new MyWebService(new MyServlet());
   }
}

运行，OK！一个web容器已经启动，当你在刚建的工程（项目）目录下丢一个HTML（比如welcome.html）,在浏览器里输入 http://127.0.0.1:2008/welcome.html,即可解析welcome.html。
（转自http://www.blogjava.net/kalman03/archive/2008/10/17/235090.html，尊重原作者的成果）