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方法根據URL，會請求文件、數據庫查詢結果、程序運行結果等多種內容 */
public void GET(String url) {
try {
checkHTTP(url);
openServer(target.getHost(),target.getPort() );
String cmd = "GET "+ getURLFormat(target) +" HTTP/1.0"
+ getBaseHeads()+"";
sendMessage(cmd);
receiveMessage();
}catch(ProtocolException p) {
p.printStackTrace();
return;
}catch(UnknownHostException e) {
e.printStackTrace();
return;
}catch(IOException i)

i.printStackTrace();
return;
}
}

/*
* HEAD方法只請求URL的元信息，不包括URL本身。若懷疑本機和服務器上的
* 文件相同，用這個方法檢查最快捷有效。
*/
public void HEAD(String url) {
try {
checkHTTP(url);
openServer(target.getHost(),target.getPort() );
String cmd = "HEAD "+getURLFormat(target)+" HTTP/1.0"
+getBaseHeads()+"";
sendMessage(cmd);
receiveMessage();
}catch(ProtocolException p) {
p.printStackTrace();
return;
}catch(UnknownHostException e) {
e.printStackTrace();
return;
}catch(IOException i)

i.printStackTrace();
return;
}
}
/*
* POST方法是向服務器傳送數據，以便服務器做出相應的處理。例如網頁上常用的
* 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"+getBaseHeads();
cmd += "Content-type: application/x-www-form-urlencoded";
cmd += "Content-length: " + content.length() + "";
cmd += content+"";
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("這不是HTTP協議");
this.target = target;
}catch(MalformedURLException m) {
throw new ProtocolException("協議格式錯誤");
}
}
/*
* 與Web服務器連接。若找不到Web服務器，InetAddress會引發UnknownHostException
* 異常。若Socket連接失敗，會引發IOException異常。
*/
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;
}
}
/* 關閉與Web服務器的連接 */
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服務器傳送數據 */
protected void sendMessage(String data) throws IOException{
sender.write(data.getBytes(),0,data.length());
sender.flush();
}
/* 接收來自Web服務器的數據 */
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==''||word=='') {
word=receiver.read();
if(word=='') 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<message.length() && message.charAt(mark+1)==32 ) mark++;
responseCode = Integer.parseInt(message.substring(mark+1,mark+=4));
responseMessage = message.substring(mark,message.length()).trim();

// 應答狀態碼和處理請讀者添加
switch(responseCode) {
case 400:
throw new IOException("錯誤請求");
case 404:
throw new FileNotFoundException( getURLFormat(target) );
case 503:
throw new IOException("服務器不可用" );
}
if(word==-1) throw new ProtocolException("信息接收異常終止");
int symbol=-1;
count=0;
// 解析元信息
while( word!='' && word!='' && word>-1) {
if(word=='') word=32;
if(count==data.length) data = addCapacity(data);
data[count++] = (byte)word;
parseLine: {
while( (symbol=receiver.read()) >-1 ) {
switch(symbol) {
case '':
symbol=32; break;
case '':
case '':
word = receiver.read();
if( symbol=='' && word=='') {
word=receiver.read();
if(word=='') word=receiver.read();
}
if( word=='' || word=='' || 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<message.length() && message.charAt(mark)<=32 ) mark++;
String value = message.substring(mark,message.length() );
header.put(key,value);
count=0;
}
// 獲得正文數據
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: myselfHttp/1.0"+
"Accept: www/source; text/html; image/gif; */*";
return inf;
}
private byte[] addCapacity(byte rece[]){
byte temp[] = new byte[rece.length+1024];
System.arraycopy(rece,0,temp,0,rece.length);
return temp;
}
}