用java开发一个简单的web服务器

来源：互联网发布：mac os x install dvd 编辑：程序博客网时间：2024/06/05 08:44

本文会初步介绍web应用中的服务器，客户端模型，帮助新人大致了解一个网络中处理请求的框架，最后用java实现了一个简单服务器(处理静。

首先指出客户端与用户端的实质，它们都是进程。(一台主机自然可以运行多个不同的客户端与服务器)

下图是客户端与服务器交互的一个基本模型

发送请求

客户端--------------------------> 服务器<--------------------------------------->资源

<------------------------ 调用资源处理请求

响应请求

我们用一个例子来说明这个模型

若我们在网站中输入一个网址(也就是一个请求)如www.google.com:80/index.html,分为三个部分。

1.www.google.com 服务器所在的主机

2.:80 80指端口号：用于与前面隔开,计算机中一个端口对应一个进程，这也再次说明服务器就是一个进程。

3./index.html 主机中的资源文件，每条由服务器返回的内容都与其管理的某个文件相关联。

有了这些基本了解我们就着手实现一个服务器。

首先创建一个服务器入口

import java.net.Socket;import java.net.ServerSocket;import java.net.InetAddress;import java.io.InputStream;import java.io.OutputStream;import java.io.IOException;public class HttpServer1 {//服务器入口处  // shutdown command  private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";  // the shutdown command received  private boolean shutdown = false;  public static void main(String[] args) {     HttpServer1 server = new HttpServer1();     server.await();  }  public void await() {    ServerSocket serverSocket = null;  //由于我们的服务器端要一直等待,所以用了ServerSocket这个类一直等待直到接收消息    int port = 8080;    try {    //设置端口号及服务器主机地址      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 {      //一个服务器必须要有一个接收流对象与一个输出流对象        socket = serverSocket.accept();        input = socket.getInputStream();        output = socket.getOutputStream();        // create Request object and parse        Request request = new Request(input);        //解析浏览器中输入的网址        request.parse();        // create Response object        Response response = new Response(output);        response.setRequest(request);               //检查是否以"/servlet/"开头(也可以以其它字母开头再对应去处理，这便是动态处理)，否则处理静态资源        if (request.getUri().startsWith("/servlet/")) {          ServletProcessor1 processor = new ServletProcessor1();          processor.process(request, response);                }        else {          StaticResourceProcessor processor = new StaticResourceProcessor();          processor.process(request, response);        }        // 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();        System.exit(1);      }    }  }}

Constants用来存储我们的文件目录

import java.io.File;public class Constants {  public static final String WEB_ROOT =    System.getProperty("user.dir") + File.separator  + "webroot";}

Request，服务器请求类的实现,还有许多接口方法没有列举出来，因为此处仅是实现一个最基本的Request故暂不实现它们。

import java.io.InputStream;import java.io.IOException;import java.io.BufferedReader;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 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 void parse() {    // 读取请求的信息    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());  }

同样Response类.

import java.io.OutputStream;import java.io.IOException;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.File;import java.io.PrintWriter;import java.util.Locale;import javax.servlet.ServletResponse;import javax.servlet.ServletOutputStream;public class Response implements ServletResponse {  private static final int BUFFER_SIZE = 1024;  Request request;  OutputStream output;  PrintWriter writer;  public Response(OutputStream output) {    this.output = output;  }  public void setRequest(Request request) {    this.request = request;  }  /* This method is used to serve a static page */  public void sendStaticResource() throws IOException {    byte[] bytes = new byte[BUFFER_SIZE];    FileInputStream fis = null;    try {      //根据我们Constant中指定目录与浏览器解析的地址去初始化一个文件。      File file = new File(Constants.WEB_ROOT, request.getUri());      fis = new FileInputStream(file);      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();    }  }

动态处理类

import java.net.URL;import java.net.URLClassLoader;import java.net.URLStreamHandler;import java.io.File;import java.io.IOException;import javax.servlet.Servlet;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;public class ServletProcessor1 {public void process(Request request, Response response) {// TODO Auto-generated method stub    String uri = request.getUri();    String servletName = uri.substring(uri.lastIndexOf("/") + 1);    URLClassLoader loader = null;    try {      // create a URLClassLoader      URL[] urls = new URL[1];      URLStreamHandler streamHandler = null;      File classPath = new File(Constants.WEB_ROOT);      // the forming of repository is taken from the createClassLoader method in      // org.apache.catalina.startup.ClassLoaderFactory            String repository = (new URL("file", null, classPath.getCanonicalPath() + File.separator)).toString() ;      System.out.println("repository="+repository);      // the code for forming the URL is taken from the addRepository method in      // org.apache.catalina.loader.StandardClassLoader class.      urls[0] = new URL(null, repository, streamHandler);      System.out.println("urls="+urls[0].toString());     // System.out.print(urls[0].toString());      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());    }}}

静态处理类

import java.io.IOException;public class StaticResourceProcessor {public void process(Request request, Response response) {// TODO Auto-generated method stub    try {        response.sendStaticResource();      }      catch (IOException e) {        e.printStackTrace();      }}}

0 0