Sunday, 3 July 2011

Controlling an executable from Java program


Windows tools like Notepad, internet explorer and other executable files can be started from java program through its core API.


Procedure to start a Notepad application from java program:

 Create an object for Runtime class
                         Runtime runtime = Runtime.getRuntime();
       
Create the command string
                         String command = "notepad.exe";        
Call exec()
                         try{
                             Process process = runtime.exec(command);
                         }catch(IOException e){
                     
                         }
         For starting Notepad application does not require Process object, but few executables requires I/O operation. In that case we will have to use the process object exclusively.

Simple program which starts Notepad:


                                                                         Fig-1.01


Procedure to start Browser in java Program:

We have seen starting a notepad application from java program, now let us start Internet Explorer with some URL.

The command string varies depending upon the OS and  Browser we are using.

1. Identify current Operating System and Browser:
                                               
        public boolean isWindowsPlatform() {
     
          String OS = System.getProperty("os.name");
          if(OS != null && OS.startsWith(WIN_ID)) {
              return true;
          }else{
              return false;
          }
    }

2. Create FLAG and PATH:
     
        Windows OS:
               Flag is used to display the URL:
                         String WIN_FLAG = "url.dll,FileProtocolHandler";
               Path is used to open the default browser:
                         String WIN_PATH = "rundll32"
                URL:
                          http://www.java.com
         Unix OS:
               Flag to display the URL:
                        String UNIX_FLAG = "-remote openURL";
               To open Netscape Navigator:
                        String UNIX_PATH = "netscape"
               URL:
                         http://www.java-gui.blogspot.com
3. Create Command String:
     
         String command = WIN_PATH+" "+WIN_FLAG+" "+URL; [windows platform]

4.  Create Runtime object and execute the command:
        Runtime runtime = Runtime.getRuntime();
          try {
                 runtime.exec(command);
          } catch(Exception e){
              e.printStackTrace();
          }

Complete program to start Browser:
/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

public class StartBrowser {

    public StartBrowser(String URL) {

       String command = null;
        // check OS
       if(isWindowsPlatform()) {

         // create command string
         command = WIN_PATH+" "+WIN_FLAG+" "+URL;
         //pass command to the exec()
         Runtime runtime = Runtime.getRuntime();
         try {
              runtime.exec(command);
         } catch(Exception e){e.printStackTrace();}
       }
    }

    public boolean isWindowsPlatform() {
        String OS = System.getProperty("os.name");
        if(OS != null && OS.startsWith(WIN_ID)) {
            return true;
        }else{
            return false;
        }
    }

    public static void main(String[] args) {
         new StartBrowser("http://www.java-gui.blogspot.com");
    }

    private static final String WIN_ID = "Windows";
    // default browser start from windows.
    private static final String WIN_PATH = "rundll32";
    // The flag to display a url.
    private static final String WIN_FLAG = "url.dll,FileProtocolHandler";
}

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