Java Tutorial/Network/URLConnection

Содержание

1 All Headers
2 Call a servlet from a Java command line application
3 Chain the InputStream to a Reader
4 Downloading a web page using URL and URLConnection classes
5 Encoding Aware Source Viewer
6 Get files updated last 24 hours
7 Get response header from HTTP request
8 Getting the Cookies from an HTTP Connection
9 Getting the Response Headers from an HTTP Connection
10 Header Viewer
11 Identify yourself using HTTP Authentification
12 java.net.URLConnection
13 Preventing Automatic Redirects in a HTTP Connection
14 Read a GIF or CLASS from an URL and save it locally
15 Read from a URL with buffered stream
16 Sending a Cookie to an HTTP Server
17 Sending a POST Request Using a URL
18 Sending a POST Request with Parameters From a Java Class
19 URLConnection.openStream is more powerful than URL.openStream
20 Writing to a Web server

All Headers

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);
    }
  }
}

Call a servlet from a Java command line application

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;
  }
}

Chain the InputStream to a Reader

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);
    }
  }
}

Downloading a web page using URL and URLConnection classes

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();
  }
}

Encoding Aware Source Viewer

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);
    }
  }
}

Get files updated last 24 hours

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);
    }
  }
}

Get response header from HTTP request

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 + ", ");
      }
    }
  }
}

Getting the Cookies from an HTTP Connection

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]);
            }
          }
        }
      }
    }
  }
}

Getting the Response Headers from an HTTP Connection

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;
      }
    }
  }
}

Header Viewer

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());
  }
}

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

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();
  }
}

java.net.URLConnection

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

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

Preventing Automatic Redirects in a HTTP Connection

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();
  }
}

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

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();
  }
}

Read from a URL with buffered stream

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();
    }
  }
}

Sending a Cookie to an HTTP Server

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();
  }
}

Sending a POST Request Using a URL

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();
  }
}

Sending a POST Request with Parameters From a Java Class

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();
  }
}

URLConnection.openStream is more powerful than URL.openStream

Reading a Web resource"s headers and content:

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();
    }
  }
}

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.

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();
  }
}

Java Tutorial/Network/URLConnection

Содержание

All Headers

Call a servlet from a Java command line application

Chain the InputStream to a Reader

Downloading a web page using URL and URLConnection classes

Encoding Aware Source Viewer

Get files updated last 24 hours

Get response header from HTTP request

Getting the Cookies from an HTTP Connection

Getting the Response Headers from an HTTP Connection

Header Viewer

Identify yourself using HTTP Authentification

java.net.URLConnection

Preventing Automatic Redirects in a HTTP Connection

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

Read from a URL with buffered stream

Sending a Cookie to an HTTP Server

Sending a POST Request Using a URL

Sending a POST Request with Parameters From a Java Class

URLConnection.openStream is more powerful than URL.openStream

Writing to a Web server

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