构建简单服务器

读how tomcat works 第一章，想把一直没有怎么搞透彻的服务器基本原理搞清楚，找来了源码，构建了一个测试的工程，把过程记录一下。

    java web 服务器的本质，主要就是实现了http协议的socket。

 1.   先来看http，分为两部分，一是请求，而是响应。

    请求部分分为如下内容：

       方法

       请求头

       请求体

     eg：

       GET /index.html HTTP/1.1
Accept: image/jpeg, application/x-ms-application, image/gif, application/xaml+xml, image/pjpeg, application/x-ms-xbap, application/x-shockwave-flash, application/msword, application/vnd.ms-powerpoint, application/vnd.ms-excel, */*
Accept-Language: zh-CN
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; QQDownload 718; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; InfoPath.3)
Accept-Encoding: gzip, deflate
Host: 127.0.0.1:8080
Connection: Keep-Alive

    【请求体为空】

    响应部分分为如下内容：

       响应状态

       响应头

       响应体

eg：

HTTP/1.1 404 File Not Found
Content-Type: text/html
Content-Length: 23

<h1>File Not Found</h1>

这个是用了    getBytes() 之后的值：  [B@a32b

2.再来看socket部分

 

3.直接上代码，一共是三个类

HttpServer

Request

Response

package com.yangpb;

import java.net.Socket;
import java.net.ServerSocket;
import java.net.InetAddress;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;
import java.io.File;

public class HttpServer {

  /** WEB_ROOT is the directory where our HTML and other files reside.
   *  For this package, WEB_ROOT is the "webroot" directory under the working
   *  directory.
   *  The working directory is the location in the file system
   *  from where the java command was invoked.
   */
  public static final String WEB_ROOT =
    System.getProperty("user.dir") + File.separator  + "webroot";

  // shutdown command
  private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";

  // the shutdown command received
  private boolean shutdown = false;

  public static void main(String[] args) {
    HttpServer server = new HttpServer();
    server.await();
  }

  public 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);
    }

    // Loop waiting for a request
    while (!shutdown) {
      Socket socket = null;
      InputStream input = null;
      OutputStream output = null;
      try {
        socket = serverSocket.accept();
        input = socket.getInputStream();
        output = socket.getOutputStream();

        // create Request object and parse
        Request request = new Request(input);
        request.parse();

        // create Response object
        Response response = new Response(output);
        response.setRequest(request);
        response.sendStaticResource();

        // Close the socket
        socket.close();

        //check if the previous URI is a shutdown command
        shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
      }
      catch (Exception e) {
        e.printStackTrace();
        continue;
      }
    }
  }
}

 

package com.yangpb;

import java.io.InputStream;
import java.io.IOException;

public class Request {

  private InputStream input;
  private String uri;

  public Request(InputStream input) {
    this.input = input;
  }

  public void parse() {
    // Read a set of characters from the socket
    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.print(request.toString());
    uri = parseUri(request.toString());
  }

  private String parseUri(String requestString) {
	  
	  
	  
	  System.out.println("requestString ==" + requestString);
    int index1, index2;
    index1 = requestString.indexOf(' ');
    if (index1 != -1) {
      index2 = requestString.indexOf(' ', index1 + 1);
      if (index2 > index1)
      {
        
    	  System.out.println("file==" + requestString.substring(index1 + 1, index2) );
    	  return requestString.substring(index1 + 1, index2);
        
      }
    }
    return null;
  }

  public String getUri() {
    return uri;
  }

}

 

package com.yangpb;

import java.io.OutputStream;
import java.io.IOException;
import java.io.FileInputStream;
import java.io.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
*/

public class Response {

  private static final int BUFFER_SIZE = 1024;
  Request request;
  OutputStream output;

  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 {
      File file = new File(HttpServer.WEB_ROOT, request.getUri());
      if (file.exists()) {
        fis = new FileInputStream(file);
        int ch = fis.read(bytes, 0, BUFFER_SIZE);
        while (ch!=-1) {
        	System.out.println("bytes==" + bytes);
          output.write(bytes, 0, ch);
          ch = fis.read(bytes, 0, BUFFER_SIZE);
        }
      }
      else {
        // file not found
        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>";
        System.out.println("errorMessage==" + errorMessage);
        System.out.println("errorMessage.getBytes()==" + errorMessage.getBytes());
        output.write(errorMessage.getBytes());
      }
    }
    catch (Exception e) {
      // thrown if cannot instantiate a File object
      System.out.println(e.toString() );
    }
    finally {
      if (fis!=null)
        fis.close();
    }
  }
}

 4.测试

本机输入：http://127.0.0.1:8080/index.html

本模拟服务器会在对应工程下面的webroot 下面找 index.html 文件，然后给返回。