Http服务器实现JAVA版

import java.net.*;
import java.io.*;
import java.util.Properties;
import java.util.Enumeration;

/**
Http客户端程序已集成在Java语言中，可以通过URLConnection类调用。遗憾的
是，由于SUN没有公布Http客户程序的源码，它实现的细节仍是一个谜。本文根据HTTP
协议规范，用Java.net.Socket类实现一个HTTP协议客户端程序。

1.Socket类:
了解TCP/IP协议集通信的读者知道，协议间的通信是通过Socket完成的。在
Java.net包中，Socket类就是对Socket的具体实现。它通过连接到主机后，返回一个
I/O流，实现协议间的信息交换。

2 . HTTP协议
HTTP协议同其它TCP/IP协议集中的协议一样，是遵循客户/服务器模型工作的。客
户端发往服务端的信息格式如下:
------------------------------
请求方法 URL HTTP协议的版本号
提交的元信息
**空行**
实体
------------------------------
请求方法是对这次连接工作的说明，目前HTTP协议已经发展到1.1版，它包括GET、
HEAD、POST、DELETE、OPTIONS、TRACE、PUT七种。元信息是关于当前请求的信息。通
过分析元信息，可以检查实体数据是否完整，接收过程是否出错，类型是否匹配等。元
信息的引入使HTTP协议通信更加稳妥可靠。实体是请求的具体内容。
将上述报文发往Web服务器，如果成功，应答格式如下:
--------------------------------
HTTP协议的版本号 应答状态码 应答状态码说明
接收的元信息
**空行**
实体
--------------------------------
以上报文发向客户端，并且接收成功，彼此间关闭连接，完成一次握手。
下面用最常用的GET方法，来说明具体的报文应用
----------------------------------
GET http://www.youhost.com HTTP/1.0
accept: www/source; text/html; image/gif; image/jpeg; *／*
User_Agent: myAgent
**空行**
-----------------------------------
这个报文是向www.youhost.com主机请求一个缺省HTML文档。客户端HTTP协议版本
号是1.0版，元信息包括可接收的文件格式，用户代理，每一段之间用回车换行符分
隔，最后以一个空行结束。发向服务器后，如果执行过程正常，服务器返回以下代码:
------------------------------------
HTTP/1.1 200 OK
Date: Tue, 14 Sep 1999 02:19:57 GMT
Server: Apache/1.2.6
Connection: close
Content-Type: text/html
**空行**
......
------------------------------------
HTTP/1.1表示这个HTTP服务器是1.1版，200是服务器对客户请求的应答状态码，OK
是对应答状态码的解释，之后是这个文档的元信息和文档正文。(相关应答状态码和元
信息的解释请参阅Inetrnet标准草案:RFC2616)。

注: 程序中只实现GET、HEAD、POST三种方法。其他几种因不常使用，暂且忽略。

*/
public class Http {
 protected Socket client;
 protected BufferedOutputStream sender;
 protected BufferedInputStream receiver;
 protected ByteArrayInputStream byteStream;
 protected URL target;
 private int responseCode=-1;
 private String responseMessage="";
 private String serverVersion="";
 private Properties header = new Properties();

 public Http() { }

 public Http(String url) {
 GET(url) ;
 }

 /* GET方法根据URL，会请求文件、数据库查询结果、程序运行结果等多种内容 */
 public void GET(String url){
  try{
   checkHTTP(url);
   openServer(target.getHost(),target.getPort() );
   String cmd = "GET " + getURLFormat(target) + " HTTP/1.0\r\n" + getBaseHeads() + "\r\n";
   sendMessage(cmd);
   receiveMessage();
  }
  catch(ProtocolException p){
   p.printStackTrace();
   return;
  }
  catch(UnknownHostException e){
   e.printStackTrace();
   return;
  }
  catch(IOException i){
   i.printStackTrace();
   return;
  }
 }

 /*
 * HEAD方法只请求URL的元信息，不包括URL本身。若怀疑本机和服务器上的
 * 文件相同，用这个方法检查最快捷有效。
 */
 public void HEAD(String url){
  try{
   checkHTTP(url);
   openServer(target.getHost(),target.getPort());
   String cmd = "HEAD " + getURLFormat(target) + " HTTP/1.0\r\n" + getBaseHeads() + "\r\n";
   sendMessage(cmd);
   receiveMessage();
  }
  catch(ProtocolException p){
   p.printStackTrace();
   return;
  }
  catch(UnknownHostException e){
   e.printStackTrace();
   return;
  }
  catch(IOException i){
   i.printStackTrace();
   return;
  }
 }

 /*
 * POST方法是向服务器传送数据，以便服务器做出相应的处理。例如网页上常用的
 * 提交表格。
 */
 public void POST(String url,String content) {
  try{
   checkHTTP(url);
   openServer(target.getHost(),target.getPort() );
   String cmd = "POST " + getURLFormat(target) + " HTTP/1.0\r\n" + getBaseHeads();
   cmd += "Content-type: application/x-www-form-urlencoded\r\n";
   cmd += "Content-length: " + content.length() + "\r\n\r\n";
   cmd += content + "\r\n";
   sendMessage(cmd);
   receiveMessage();
  }
  catch(ProtocolException p){
   p.printStackTrace();
   return;
  }
  catch(UnknownHostException e){
   e.printStackTrace();
   return;
  }
  catch(IOException i){
   i.printStackTrace();
   return;
  }

 }

 protected void checkHTTP(String url) throws ProtocolException {
  try{
   URL target = new URL(url);
   if(target == null || !target.getProtocol().toUpperCase().equals("HTTP")){
    throw new ProtocolException("这不是HTTP协议");
   }
   this.target = target;
  }
  catch(MalformedURLException m) {
   throw new ProtocolException("协议格式错误");
  }
 }

 /*
 * 与Web服务器连接。若找不到Web服务器，InetAddress会引发UnknownHostException
 * 异常。若Socket连接失败，会引发IOException异常。
 */
 protected void openServer(String host,int port) throws UnknownHostException,IOException {
  header.clear();
  responseMessage="";
  responseCode=-1;

  if(client!=null){
   closeServer();
  }
  if(byteStream != null){
   byteStream.close();
   byteStream=null;
  }

  InetAddress address = InetAddress.getByName(host);
  client = new Socket(address,port==-1 80:port);
  client.setSoTimeout(5000);
  sender = new BufferedOutputStream(client.getOutputStream());
  receiver = new BufferedInputStream(client.getInputStream());
 }

 /* 关闭与Web服务器的连接 */
 protected void closeServer() throws IOException {
  if(client==null){
   return;
  }
  try{
   client.close();
   sender.close();
   receiver.close();
  }
  catch(IOException i){
   throw i;
  }

  client=null;
  sender=null;
  receiver=null;
 }

 protected String getURLFormat(URL target) {
  String spec = "http://" + target.getHost();
  if(target.getPort()!=-1){
   spec+=":"+target.getPort();
  }

  return spec+=target.getFile();
 }

 /* 向Web服务器传送数据 */
 protected void sendMessage(String data) throws IOException{
  sender.write(data.getBytes(),0,data.length());
  sender.flush();
 }

 /* 接收来自Web服务器的数据 */
 protected void receiveMessage() throws IOException{
  byte data[] = new byte[1024];
  int count=0;
  int word=-1;
  // 解析第一行
  while( (word=receiver.read())!=-1 ) {
   if(word=='\r'||word=='\n') {
    word=receiver.read();
    if(word=='\n') word=receiver.read();
    break;
   }
   if(count == data.length) data = addCapacity(data);
   data[count++]=(byte)word;
  }
  String message = new String(data,0,count);
  int mark = message.indexOf(32);
  serverVersion = message.substring(0,mark);
  while( mark
  responseCode = Integer.parseInt(message.substring(mark+1,mark+=4));
  responseMessage = message.substring(mark,message.length()).trim();

  // 应答状态码和处理请读者添加
  switch(responseCode) {
   case 400:
    throw new IOException("错误请求");
   case 404:
    throw new FileNotFoundException( getURLFormat(target) );
   case 503:
    throw new IOException("服务器不可用" );
  }
  if(word==-1) throw new ProtocolException("信息接收异常终止");
  int symbol=-1;
  count=0;
  // 解析元信息
  while( word!='\r' && word!='\n' && word>-1) {
   if(word=='\t') word=32;
   if(count==data.length) data = addCapacity(data);
   data[count++] = (byte)word;
   parseLine: {
    while( (symbol=receiver.read()) >-1 ) {
     switch(symbol) {
     case '\t':
     symbol=32; break;
     case '\r':
     case '\n':
     word = receiver.read();
     if( symbol=='\r' && word=='\n') {
     word=receiver.read();
     if(word=='\r') word=receiver.read();
     }
     if( word=='\r' || word=='\n' || word>32) break parseLine;
     symbol=32; break;
     }
     if(count==data.length) data = addCapacity(data);
     data[count++] = (byte)symbol;
    }
    word=-1;
   }
   message = new String(data,0,count);
   mark = message.indexOf(':');
   String key = null;
   if(mark>0) key = message.substring(0,mark);
   mark++;
   while( mark
<="32">   String value = message.substring(mark,message.length() );
   header.put(key,value);
   count=0;
  }
  // 获得正文数据
  while( (word=receiver.read())!=-1) {
  if(count == data.length) data = addCapacity(data);
  data[count++] = (byte)word;
  }
  if(count>0) byteStream = new ByteArrayInputStream(data,0,count);
  data=null;
  closeServer();
 }

 public String getResponseMessage() {
  return responseMessage;
 }

 public int getResponseCode() {
  return responseCode;
 }

 public String getServerVersion() {
  return serverVersion;
 }

 public InputStream getInputStream() {
  return byteStream;
 }

 public synchronized String getHeaderKey(int i) {
  if(i>=header.size()){
   return null;
  }
  Enumeration enum = header.propertyNames();
  String key = null;
  for(int j=0; j<=i; j++){
   key = (String)enum.nextElement();
  }
  return key;
 }

 public synchronized String getHeaderValue(int i) {
  if(i>=header.size()) return null;
  return header.getProperty(getHeaderKey(i));
 }

 public synchronized String getHeaderValue(String key) {
  return header.getProperty(key);
 }

 protected String getBaseHeads() {
  String inf = "User-Agent: IcewolfHttp/1.0\r\nAccept: www/source; text/html; image/gif; */*\r\n";
  return inf;
 }

 private byte[] addCapacity(byte rece[]){
  byte temp[] = new byte[rece.length+1024];
  System.arraycopy(rece,0,temp,0,rece.length);
  return temp;
 }

 public static void main(String [] args){
  /*
  Http p = new Http();
  p.GET("http://www.google.com/search q=java+book");
  byte[] bGets = new byte[1024];
  ByteArrayInputStream pS = (ByteArrayInputStream)p.getInputStream();
  int offset = 0;
  while((offset=pS.read(bGets,0,1024)) != -1){
   System.out.print(new String(bGets,0,offset));
  }
  */
  String target = "http://www.google.com/search q=java+book";
  try {
   URL url = new URL(target);
   HttpURLConnection pconn = (HttpURLConnection)url.openConnection();
   //HttpURLConnection.setFollowRedirects(true);
   //pconn.setInstanceFollowRedirects(true);
   pconn.addRequestProperty("User-Agent","IcewolfHttp/1.0");
   pconn.addRequestProperty("Accept","www/source; text/html; image/gif; */*");
   
   pconn.connect();
   System.out.println("Connect status:"+pconn.getResponseCode());
   //if(HttpURLConnection.HTTP_ACCEPTED == pconn.getResponseCode())
   //InputStream in = url.openConnection();

   InputStream in = pconn.getInputStream();
   System.out.println("Get status:"+pconn.getResponseCode());
   BufferedInputStream buff = new BufferedInputStream(in);
   Reader r = new InputStreamReader(buff);
   int c = 0;
   while ( (c = r.read()) != -1){
    System.out.print((char)c);
   }
   buff.close();
   in.close();
   pconn.disconnect();
  } catch (MalformedURLException mfe) {
   System.err.println(target + " is not a parsable URL");
  } catch (IOException ioe) {
   System.err.println(ioe);
  }

 }
}