Java Source Viewer,View Source of HTML File Using Java Program,View Source Example in Java

This section illustrates you the procedure of viewing complete html code of a page i.e. running on the server. This section provides you an example with the complete code of the program which views the html source code of your given page running on server. Following program strictly takes a url (Uniform Resource Locator) started with the "http://" otherwise it will generate an error which is caught by the MalformedURLException in catch block.


import java.io.*;

import java.net.*;



public class SourceViewer{

  public static void main (String[] args) throws IOException{

    System.out.print("Enter url of local for viewing html source code: ");

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

    String url = br.readLine();

    try{

      URL u = new URL(url);

      HttpURLConnection uc = (HttpURLConnection) u.openConnection();

      int code = uc.getResponseCode();

      String response = uc.getResponseMessage();

      System.out.println("HTTP/1.x " + code + " " + response);

      for(int j = 1; ; j++){

        String header = uc.getHeaderField(j);

        String key = uc.getHeaderFieldKey(j);

        if(header == null || key == null)

          break;

        System.out.println(uc.getHeaderFieldKey(j) + ": " + header);

      }

      InputStream in = new BufferedInputStream(uc.getInputStream());

      Reader r = new InputStreamReader(in);

      int c;

      while((c = r.read()) != -1){

        System.out.print((char)c);

      }

    }

    catch(MalformedURLException ex){

      System.err.println(url + " is not a valid URL.");

    }

    catch(IOException ie){

      System.out.println("Input/Output Error: " + ie.getMessage());

    }

  }

}

Following program takes an url name which should be started with "http://" otherwise it will generate an error like this:

And if the file name (given through the url) exists then the program gives you the complete html source code of the file.

Various methods and APIs have been used in the above program. These are illustrated as follows:

HttpURLConnection:
This is the abstract class of the java.net package. This class extends the URLConnection class of the java.net package and facilitates all same facilities of the URLConnection class with the specific HTTP features specially.

getResponseCode():
This is the method of the HttpURLConnection class that returns a integer value which is the code for the status from the http response message.

getResponseMethod():
This is also the method of the HttpURLConnection class that show the message with the http response code from the server.

getHeaderFieldKey(int j):
Above method returns the key for the given j^th header field. Given j is the argument of the method. And this method returns the String type value that will be the key value.

Downloading and Viewing html source of a page i.e. running on the server