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**
＜html＞＜head＞...＜/head＞＜body＞...＜/body＞＜/html＞
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)。
3. HTTP客户端程序:
import java.net.*;
import java.io.*;
import java.util.Properties;
import java.util.Enumeration;
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;
try {
if(client!=null) closeServer();
if(byteStream != null) {
byteStream.close(); byteStream=null;
}
InetAddress address = InetAddress.getByName(host);
client = new Socket(address,port==-1?80:port);
sender = new BufferedOutputStream(client.getOutputStream());
receiver = new BufferedInputStream(client.getInputStream());
}catch(UnknownHostException u) {
throw u;
}catch(IOException i) {
throw i;
}
}
/* 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( mark0) 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: myselfHttp/1.0\r\n"+
"Accept: 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;
}
}
(责任编辑：包春林)
