Java Tutorial/Network/URLConnection

Материал из Java эксперт
Перейти к: навигация, поиск

All Headers

   <source lang="java">

import java.net.URL; import java.net.URLConnection; public class MainClass { 

 public static void main(String args[]) throws Exception {
   URL u = new URL("http://www.jexp.ru");
   URLConnection uc = u.openConnection();
   for (int j = 1;; j++) {
     String header = uc.getHeaderField(j);
     if (header == null)
       break;
     System.out.println(uc.getHeaderFieldKey(j) + ": " + header);
   }
 }

}</source>





Call a servlet from a Java command line application

   <source lang="java">

import java.io.ByteArrayOutputStream; import java.io.DataInputStream; import java.io.DataOutputStream; public class CounterApp { 

 String servletURL;
 String sessionCookie = null;
 public static void main(String args[]) {
   if (args.length == 0) {
     System.out.println("\nServlet URL must be specified");
     return;
   }
   try {
     CounterApp app = new CounterApp(args[0]);
     for (int i = 1; i <= 5; i++) {
       int count = app.getCount();
       System.out.println("Pass " + i + " count=" + count);
     }
   } catch (Exception ex) {
     ex.printStackTrace();
   }
 }
 public CounterApp(String url) {
   servletURL = url;
 }
 public int getCount() throws Exception {
   java.net.URL url = new java.net.URL(servletURL);
   java.net.URLConnection con = url.openConnection();
   if (sessionCookie != null) {
     con.setRequestProperty("cookie", sessionCookie);
   }
   con.setUseCaches(false);
   con.setDoOutput(true);
   con.setDoInput(true);
   ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
   DataOutputStream out = new DataOutputStream(byteOut);
   out.flush();
   byte buf[] = byteOut.toByteArray();
   con.setRequestProperty("Content-type", "application/octet-stream");
   con.setRequestProperty("Content-length", "" + buf.length);
   DataOutputStream dataOut = new DataOutputStream(con.getOutputStream());
   dataOut.write(buf);
   dataOut.flush();
   dataOut.close();
   DataInputStream in = new DataInputStream(con.getInputStream());
   int count = in.readInt();
   in.close();
   if (sessionCookie == null) {
     String cookie = con.getHeaderField("set-cookie");
     if (cookie != null) {
       sessionCookie = parseCookie(cookie);
       System.out.println("Setting session ID=" + sessionCookie);
     }
   }
   return count;
 }
 public String parseCookie(String raw) {
   String c = raw;
   if (raw != null) {
     int endIndex = raw.indexOf(";");
     if (endIndex >= 0) {
       c = raw.substring(0, endIndex);
     }
   }
   return c;
 }

}</source>





Chain the InputStream to a Reader

   <source lang="java">

import java.io.BufferedInputStream; import java.io.InputStream; import java.io.InputStreamReader; import java.io.Reader; import java.net.URL; import java.net.URLConnection; public class MainClass { 

 public static void main(String[] args) throws Exception {
   URL u = new URL("http://www.jexp.ru");
   URLConnection uc = u.openConnection();
   InputStream raw = uc.getInputStream();
   InputStream buffer = new BufferedInputStream(raw);
   // chain the InputStream to a Reader
   Reader r = new InputStreamReader(buffer);
   int c;
   while ((c = r.read()) != -1) {
     System.out.print((char) c);
   }
 }

}</source>





Downloading a web page using URL and URLConnection classes

   <source lang="java">

import java.io.BufferedInputStream; import java.net.URL; import java.net.URLConnection; public class Main { 

 public static void main(String[] args) throws Exception {
   URLConnection urlc = new URL("http://www.google.ru").openConnection();
   BufferedInputStream buffer = new BufferedInputStream(urlc.getInputStream());
   
   int byteRead;
   while ((byteRead = buffer.read()) != -1){
     System.out.println((char) byteRead);
   }
   buffer.close();
 }

}</source>





Encoding Aware Source Viewer

   <source lang="java">

import java.io.BufferedInputStream; import java.io.InputStream; import java.io.InputStreamReader; import java.io.Reader; import java.net.URL; import java.net.URLConnection; public class MainClass { 

 public static void main(String[] args) throws Exception {
   String encoding = "ISO-8859-1";
   URL u = new URL("http://www.jexp.ru");
   URLConnection uc = u.openConnection();
   String contentType = uc.getContentType();
   int encodingStart = contentType.indexOf("charset=");
   if (encodingStart != -1) {
     encoding = contentType.substring(encodingStart + 8);
   }
   InputStream in = new BufferedInputStream(uc.getInputStream());
   Reader r = new InputStreamReader(in, encoding);
   int c;
   while ((c = r.read()) != -1) {
     System.out.print((char) c);
   }
 }

}</source>





Get files updated last 24 hours

   <source lang="java">

import java.io.BufferedInputStream; import java.io.InputStream; import java.io.InputStreamReader; import java.io.Reader; import java.net.URL; import java.net.URLConnection; import java.util.Date; public class MainClass { 

 public static void main(String[] args) throws Exception {
   Date today = new Date();
   long millisecondsPerDay = 24 * 60 * 60 * 1000;
   URL u = new URL("http://www.jexp.ru");
   URLConnection uc = u.openConnection();
   uc.setIfModifiedSince((new Date(today.getTime() - millisecondsPerDay)).getTime());
   InputStream in = new BufferedInputStream(uc.getInputStream());
   Reader r = new InputStreamReader(in);
   int c;
   while ((c = r.read()) != -1) {
     System.out.print((char) c);
   }
 }

}</source>





Get response header from HTTP request

   <source lang="java">

import java.net.URL; import java.net.URLConnection; import java.util.Iterator; import java.util.List; import java.util.Map; public class Main { 

 public static void main(String[] args) throws Exception {
   URL url = new URL("http://www.google.ru/index.html");
   URLConnection connection = url.openConnection();
   Map responseMap = connection.getHeaderFields();
   for (Iterator iterator = responseMap.keySet().iterator(); iterator.hasNext();) {
     String key = (String) iterator.next();
     System.out.println(key + " = ");
     List values = (List) responseMap.get(key);
     for (int i = 0; i < values.size(); i++) {
       Object o = values.get(i);
       System.out.println(o + ", ");
     }
   }
 }

}</source>





Getting the Cookies from an HTTP Connection

   <source lang="java">

import java.net.URL; import java.net.URLConnection; public class Main { 

 public static void main(String[] argv) throws Exception {
   URL url = new URL("http://hostname:80");
   URLConnection conn = url.openConnection();
   for (int i = 0;; i++) {
     String headerName = conn.getHeaderFieldKey(i);
     String headerValue = conn.getHeaderField(i);
     if (headerName == null && headerValue == null) {
       break;
     }
     if ("Set-Cookie".equalsIgnoreCase(headerName)) {
       String[] fields = headerValue.split(";\\s*");
       for (int j = 1; j < fields.length; j++) {
         if ("secure".equalsIgnoreCase(fields[j])) {
           System.out.println("secure=true");
         } else if (fields[j].indexOf("=") > 0) {
           String[] f = fields[j].split("=");
           if ("expires".equalsIgnoreCase(f[0])) {
             System.out.println("expires"+ f[1]);
           } else if ("domain".equalsIgnoreCase(f[0])) {
             System.out.println("domain"+ f[1]);
           } else if ("path".equalsIgnoreCase(f[0])) {
             System.out.println("path"+ f[1]);
           }
         }
       }
     }
   }
 }

}</source>





Getting the Response Headers from an HTTP Connection

   <source lang="java">

import java.net.URL; import java.net.URLConnection; public class Main { 

 public static void main(String[] argv) throws Exception {
   URL url = new URL("http://hostname:80");
   URLConnection conn = url.openConnection();
   for (int i = 0;; i++) {
     String headerName = conn.getHeaderFieldKey(i);
     String headerValue = conn.getHeaderField(i);
     System.out.println(headerName);
     System.out.println(headerValue);
     if (headerName == null && headerValue == null) {
       System.out.println("No more headers");
       break;
     }
   }
 }

}</source>





Header Viewer

   <source lang="java">

import java.net.URL; import java.net.URLConnection; import java.util.Date; public class MainClass { 

 public static void main(String args[]) throws Exception {
   URL u = new URL("http://www.jexp.ru");
   URLConnection uc = u.openConnection();
   System.out.println("Content-type: " + uc.getContentType());
   System.out.println("Content-encoding: " + uc.getContentEncoding());
   System.out.println("Date: " + new Date(uc.getDate()));
   System.out.println("Last modified: " + new Date(uc.getLastModified()));
   System.out.println("Expiration date: " + new Date(uc.getExpiration()));
   System.out.println("Content-length: " + uc.getContentLength());
 }

}</source> 



Content-type: text/html
Content-encoding: null
Date: Thu May 24 18:41:00 PDT 2007
Last modified: Fri May 18 08:20:08 PDT 2007
Expiration date: Wed Dec 31 16:00:00 PST 1969
Content-length: 345648


Identify yourself using HTTP Authentification

   <source lang="java">

import java.io.InputStream; import java.net.URL; import java.net.URLConnection; public class Main { 

 public static void main(String[] argv) throws Exception {
   
   URLConnection conn = new URL("http://www.yourserver.ru").openConnection();
   conn.setDoInput(true);
   conn.setRequestProperty("Authorization", "asdfasdf");
   conn.connect();
   InputStream in = conn.getInputStream();
 }

}</source>





java.net.URLConnection

  1. A URLConnection object represents a connection to a remote machine.
  2. You use it to read a resource from and write to a remote machine.
  3. To obtain an instance of URLConnection, call the openConnection method on a URL object.
  4. To use a URLConnection object to write: set the value of doOutput to true using setDoOutput methods:



   <source lang="java">

URL url = new URL ("http://www.google.ru/"); InputStream inputStream = url.openStream ();</source>





Preventing Automatic Redirects in a HTTP Connection

   <source lang="java">

import java.net.HttpURLConnection; import java.net.URL; import java.net.URLConnection; public class Main { 

 public static void main(String[] argv) throws Exception {
   HttpURLConnection.setFollowRedirects(false);
   URL url = new URL("http://hostname:80");
   URLConnection conn = url.openConnection();
   HttpURLConnection httpConn = (HttpURLConnection) conn;
   httpConn.setInstanceFollowRedirects(false);
   conn.connect();
 }

}</source>





Read a GIF or CLASS from an URL and save it locally

   <source lang="java">

import java.io.DataInputStream; import java.io.FileOutputStream; import java.net.URL; import java.net.URLConnection; public class Main { 

 public static void main(String args[]) throws Exception {
   byte[] b = new byte[1];
   URL url = new URL("http://www.server.ru/a.gif");
   URLConnection urlConnection = url.openConnection();
   urlConnection.connect();
   DataInputStream di = new DataInputStream(urlConnection.getInputStream());
   FileOutputStream fo = new FileOutputStream("a.gif");
   while (-1 != di.read(b, 0, 1))
     fo.write(b, 0, 1);
   di.close();
   fo.close();
 }

}</source>





Read from a URL with buffered stream

   <source lang="java">

import java.io.BufferedReader; import java.io.InputStreamReader; import java.net.URL; import java.net.URLConnection; public class MainClass { 

 public static void main(String[] args) throws Exception {
   URL u = new URL(args[0]);
   URLConnection uc = u.openConnection();
   BufferedReader br = new BufferedReader(new InputStreamReader(uc.getInputStream()));
   String s = br.readLine();
   while (s != null) {
     System.out.println(s);
     s = br.readLine();
   }
 }

}</source>





Sending a Cookie to an HTTP Server

   <source lang="java">

import java.net.URL; import java.net.URLConnection; public class Main { 

 public static void main(String[] argv) throws Exception {
   URL url = new URL("http://hostname:80");
   URLConnection conn = url.openConnection();
   conn.setRequestProperty("Cookie", "name1=value1; name2=value2");
   conn.connect();
 }

}</source>





Sending a POST Request Using a URL

   <source lang="java">

import java.io.BufferedReader; import java.io.InputStreamReader; import java.io.OutputStreamWriter; import java.net.URL; import java.net.URLConnection; import java.net.URLEncoder; public class Main { 

 public static void main(String[] argv) throws Exception {
   String data = URLEncoder.encode("key1", "UTF-8") + "=" + URLEncoder.encode("value1", "UTF-8");
   data += "&" + URLEncoder.encode("key2", "UTF-8") + "=" + URLEncoder.encode("value2", "UTF-8");
   URL url = new URL("http://server.ru:80/cgi");
   URLConnection conn = url.openConnection();
   conn.setDoOutput(true);
   OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
   wr.write(data);
   wr.flush();
   BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
   String line;
   while ((line = rd.readLine()) != null) {
     System.out.println(line);
   }
   wr.close();
   rd.close();
 }

}</source>





Sending a POST Request with Parameters From a Java Class

   <source lang="java">

import java.io.BufferedReader; import java.io.InputStreamReader; import java.io.OutputStreamWriter; import java.net.URL; import java.net.URLConnection; public class Main { 

 public static void main(String[] args) throws Exception {
   URL url = new URL("http://www.jexp.ru");
   URLConnection conn = url.openConnection();
   conn.setDoOutput(true);
   OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());
   writer.write("value=1&anotherValue=1");
   writer.flush();
   String line;
   BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
   while ((line = reader.readLine()) != null) {
     System.out.println(line);
   }
   writer.close();
   reader.close();
 }

}</source>





URLConnection.openStream is more powerful than URL.openStream

Reading a Web resource"s headers and content:



   <source lang="java">

import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.MalformedURLException; import java.net.URL; import java.net.URLConnection; import java.util.List; import java.util.Map; import java.util.Set; public class MainClass { 

 public static void main(String[] args) {
   try {
     URL url = new URL("http://www.jexp.ru/");
     URLConnection urlConnection = url.openConnection();
     Map<String, List<String>> headers = urlConnection.getHeaderFields();
     Set<Map.Entry<String, List<String>>> entrySet = headers.entrySet();
     for (Map.Entry<String, List<String>> entry : entrySet) {
       String headerName = entry.getKey();
       System.out.println("Header Name:" + headerName);
       List<String> headerValues = entry.getValue();
       for (String value : headerValues) {
         System.out.print("Header value:" + value);
       }
       System.out.println();
       System.out.println();
     }
     InputStream inputStream = urlConnection.getInputStream();
     BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
     String line = bufferedReader.readLine();
     while (line != null) {
       System.out.println(line);
       line = bufferedReader.readLine();
     }
     bufferedReader.close();
   } catch (MalformedURLException e) {
     e.printStackTrace();
   } catch (IOException e) {
     e.printStackTrace();
   }
 }

}</source> 



Header Name:Content-Length
Header value:329495
Header Name:X-Powered-By
Header value:ASP.NET
Header Name:ETag
Header value:"30d67746a17c71:11e5"
Header Name:null
Header value:HTTP/1.1 200 OK
Header Name:Date
Header value:Fri, 26 Jan 2007 17:02:42 GMT
Header Name:Accept-Ranges
Header value:bytes
Header Name:Content-Type
Header value:text/html
Header Name:Server
Header value:Microsoft-IIS/6.0
Header Name:Last-Modified
Header value:Mon, 04 Dec 2006 06:04:11 GMT
Header Name:Content-Location
Header value:http://www.jexp.ru/index.htm


Writing to a Web server

You can use a URLConnection object to send an HTTP request.



   <source lang="java">

import java.io.PrintWriter; import java.net.URL; import java.net.URLConnection; public class MainClass { 

 public static void main(String[] a)throws Exception {
   URL url = new URL("http://www.yourdomain.ru/form.jsp");
   URLConnection connection = url.openConnection();
   connection.setDoOutput(true);
   PrintWriter out = new PrintWriter(connection.getOutputStream());
   out.println("firstName=Joe");
   out.println("lastName=Average");
   out.close();
 }

}</source>


Источник — «http://jexp.ru/index.php?title=Java_Tutorial/Network/URLConnection&oldid=4640»