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);
}
}
}
