用Socket类实现HTTP协议客户端应用

下载本文示例代码
　　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/1.0accept: www/source; text/html; image/gif; image/jpeg; */*User_Agent: myAgent**空行** 　　这个报文是向主机请求一个缺省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 OKDate: Tue, 14 Sep 1999 02:19:57 GMTServer: Apache/1.2.6Connection: closeContent-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) throwsUnknownHostException,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;}} 　　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。 　　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/1.0accept: www/source; text/html; image/gif; image/jpeg; */*User_Agent: myAgent**空行** 　　这个报文是向主机请求一个缺省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 OKDate: Tue, 14 Sep 1999 02:19:57 GMTServer: Apache/1.2.6Connection: closeContent-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) throwsUnknownHostException,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;}} 　　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。 下载本文示例代码


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