CN Lab-6
// Socket programming to download image from web
import java.net.*;
import java.io.*;
public class WebClientImage
{
public static void main(String[] args) throws Exception
{
//open a socket to the URL www.java2s.com"
InetAddress IPobject=InetAddress.getByName("www.bits-pilani.ac.in");
Socket Fromclient= new Socket(IPobject,80);
PrintWriter OutToServer= new PrintWriter(Fromclient.getOutputStream());
OutToServer.println("GET //Uploads/Campus/BITS_Dubai_campus_logo.gif HTTP/1.1");
OutToServer.println("Host: www.bits-.pilani.ac.in");
OutToServer.println("");//send a blank line
OutToServer.flush();//do not forget
InputStream InputFromServ= Fromclient.getInputStream();// attach an inputstream to socket
File Fileobj= new File("C:\\Users\\test\\Downloads\\Image.gif");
FileOutputStream OutToFile= new FileOutputStream(Fileobj);
byte[] ImageBytes= new byte[2048];
//read block of data via inputstream and put it into the defined byte array
int length;
boolean HeadersComplete=false;
while((length=InputFromServ.read(ImageBytes))!=-1)
{
if(HeadersComplete)// already got rid of all the headers
{
OutToFile.write(ImageBytes,0,length);//for further image data from server
//after /r/n/r/n detected
}
else// still yet to get rid of end of headers
{
for(int i=0;i< 2045;i++)
{
if(ImageBytes[i]==13 && ImageBytes[i+1]==10 && ImageBytes[i+2]==13 && ImageBytes[i+3]==10)
{
HeadersComplete=true;
OutToFile.write(ImageBytes,i+4,2048-i-4);
break;// first time end of headers detected
}
}//end of for loop
}// end of else
//OutToFile.write(ImageBytes,0,length);
}// end of while
OutToFile.flush();//flush the fileoutputstream to push all information
// Fileobj.close();
}
}
WRITE A PROGRAM TO DOWNLOAD THE IMAGE OF YOUR FAVORITE CARTOON CHARACTER USING HTTPURLCONNECTION OBJECT CLASS IN JAVA.NET PACKAGE
In Java, we can use the classes URL and HttpURLConnection in the package java.net to programmatically download a file from a given URL by following these steps:
- Create a URL object for a given URL. The URL can be either:
- A direct link which contains the real file name at the end, for example:
http://jdbc.postgresql.org/download/postgresql-9.2-1002.jdbc4.jar
- An indirect link which does not contain the real file name, for example:
http://myserver.com/download?id=1234
- Open connection on the URL object – which would return an HttpURLConnection object if the URL is an HTTP URL.
- Open the input stream of the opened connection.
- Create an output stream to save file to disk.
- Repeatedly read array of bytes from the input stream and write them to the output stream, until the input stream is empty.
- Close the input stream, the output stream and the connection.
For the purpose of reusability, we create a utility class as follows:
import
java.io.File;
import
java.io.FileOutputStream;
import
java.io.IOException;
import
java.io.InputStream;
import
java.net.HttpURLConnection;
import
java.net.URL;
/**
* A utility that downloads a file from a URL.
* @author www.codejava.net
*
*/
public
class
HttpDownloadUtility {
private
static
final
int
BUFFER_SIZE = 4096;
/**
* Downloads a file from a URL
* @param fileURL HTTP URL of the file to be downloaded
* @param saveDir path of the directory to save the file
* @throws IOException
*/
public
static
void
downloadFile(String fileURL, String saveDir)
throws
IOException {
URL url = new
URL(fileURL);
HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
int
responseCode = httpConn.getResponseCode();
// always check HTTP response code first
if
(responseCode == HttpURLConnection.HTTP_OK) {
String fileName = "";
String disposition = httpConn.getHeaderField("Content-Disposition");
String contentType = httpConn.getContentType();
int
contentLength = httpConn.getContentLength();
if
(disposition != null) {
// extracts file name from header field
int
index = disposition.indexOf("filename=");
if
(index > 0) {
fileName = disposition.substring(index + 10,
disposition.length() - 1);
}
} else
{
// extracts file name from URL
fileName = fileURL.substring(fileURL.lastIndexOf("/") + 1,
fileURL.length());
}
System.out.println("Content-Type = "
+ contentType);
System.out.println("Content-Disposition = "
+ disposition);
System.out.println("Content-Length = "
+ contentLength);
System.out.println("fileName = "
+ fileName);
// opens input stream from the HTTP connection
InputStream inputStream = httpConn.getInputStream();
String saveFilePath = saveDir + File.separator + fileName;
// opens an output stream to save into file
FileOutputStream outputStream = new
FileOutputStream(saveFilePath);
int
bytesRead = -1;
byte[] buffer = new
byte[BUFFER_SIZE];
while
((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.close();
inputStream.close();
System.out.println("File downloaded");
} else
{
System.out.println("No file to download. Server replied HTTP code: "
+ responseCode);
}
httpConn.disconnect();
}
}