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-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=header.size()){
???return null;
??}
??Enumeration enum = header.propertyNames();
??String key = null;
??for(int j=0; j=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);
??}
?}
}
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