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.
<pre>
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**
<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)。
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。
</pre>
*/
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 < message.length() && message.charAt(mark + 1 ) == 32 ) {
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 < message.length() && message.charAt(mark) <= 32 ) {
mark ++ ;
}
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 enumss = header.propertyNames();
String key = null ;
for ( int j = 0 ; j <= i; j ++ ){
key = (String) enumss.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: ZealHttp/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;
}
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