File download using HTTP Socket

// Socket Programming

// File download using Http Socket

import java.io.*;

import java.net.*;

public class Filedownload

{

     private final static int BUF_SIZE = 4096;

    

     public static void downloadFile(String fileURL, String targetDir) throws IOException

     {

          URL url = new URL(fileURL);

    

          // Establish connection to remote URL

          HttpURLConnection conc = (HttpURLConnection) url.openConnection();

         

          // Check response code for connection status.

          // Use static variable (HttpURLConnection.HTTP_OK) or its code (200).

          int responseCode = conc.getResponseCode();

          // if (responseCode == HttpURLConnection.HTTP_OK)

          if (responseCode == 200)         

          {

              // Get information about the file and its content

              String fileName = "";

              String content = conc.getHeaderField("Content-Disposition");

              String contentType = conc.getContentType();

              int contentLength = conc.getContentLength();

              if (content != null)

              {

                   // Extract file name from header field

                   int index = content.indexOf("filename=");

                   if (index > 0)

                   {

                        fileName = content.substring(index + 10,content.length() - 1);

                   }

              }

              else

              {

                   // Extract file name from URL

                   fileName = fileURL.substring(fileURL.lastIndexOf("/") + 1, fileURL.length());

              }

System.out.println("Content-Type = " + contentType);

System.out.println("Content-Length = " + contentLength);

System.out.println("fileName = " + fileName);

// Open input stream from the HTTP connection

InputStream in = conc.getInputStream();

String filepath = targetDir + File.separator + fileName;

// Open output stream to save content to file

FileOutputStream out = new FileOutputStream(filepath);

                            

int data = -1;

byte[] buf = new byte[BUF_SIZE];

              while ((data = in.read(buf)) != -1)

              {

                   out.write(buf, 0, data);

              }

out.close();

in.close();

System.out.println("File downloaded");

}

else

{

System.out.println("No file to download. ");

System.out.println("Server replied HTTP code: " + responseCode);

}

conc.disconnect();

     }

         

public static void main(String[] args)

{

String fileURL = "http://drranurekha.com/wp-content/uploads/2018/02/3-Segmentation.pdf";

         

String targetDir = "D:/cnlab/Http_socket";

       

try

{

     downloadFile(fileURL, targetDir);

}

catch (IOException E)

{

     E.printStackTrace();

}

}

}

/*

Note 1: Specify the URL for file to download clearly

Example:

     Open a pdf file in BROWSER.

     Check the address bar and copy the link in url=""

     Paste it in string fileURL

*/

/*

Note 2:

response code retrieves the status of the http connection.

Example:

     HTTP_OK - HTTP Status-Code 200: OK.

     HTTP_ACCEPTED - HTTP Status-Code 202: Accepted.

     HTTP_NO_CONTENT - HTTP Status-Code 204: No Content.

     HTTP_FORBIDDEN - HTTP Status-Code 403: Forbidden.

     HTTP_CLIENT_TIMEOUT - HTTP Status-Code 408: Request Time-Out.

     HTTP_BAD_GATEWAY - HTTP Status-Code 502: Bad Gateway.

*/

/*

Note 3:

The MIME Content-disposition header provides presentation information for the body-part. It is often added to attachments specifying whether the attachment body part should be displayed (inline) or presented as a file name to be copied (attachment)

*/

Sample Output:

> javac Filedownload.java

> java Filedownload

Content-Type = application/pdf

Content-Length = 211589

fileName = 3-Segmentation.pdf

File downloaded

>