refreshing the page automatically if the configuration file changes

Hi All,

Am trying to create a small web page in JSP in which it will get it css file name from a configuration file and load it , if the values in the confiugration file has been changed then this jsp page should be refreshed automically

I have write and collect some code from the net but am getting some error

the following are the files

1. index.jsp

<jsp:useBean id="man" class="test.CheckingFileChange"/>
  <html>
   <head>
   <LINK href="<jsp:getProperty name='man' property='cssFileName'/>" rel="stylesheet" type="text/css">
  <title>JSP Page</title>
  </head>
   <body>
   <form>
   <h2><root>Hello World!</root></h2>
   </form>
    </body>
  </html>

2.servlet called "CheckingFileChange.java"

package test;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.sun.mail.iap.Response;

/**
 * Servlet implementation class CheckingFileChange
 */
public class CheckingFileChange extends HttpServlet implements FileChangeListener {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
	public CheckingFileChange(boolean b) {
    	System.out.println("Example Construcator");
        this.useClasspath = b;
	reloadProperties();
    }
	
    public CheckingFileChange() {
        //super();
        // TODO Auto-generated constructor stub
    	reloadProperties();
    	System.out.println("here we are inside checking the super");
    }

/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//super.doGet(request, response);
		System.out.println("hi am here get");
		
		response.sendRedirect("index.jsp");
		System.out.println("Going to checkFileChangeOrNot() ");
		checkFileChangeOrNot();
		
	}

/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		System.out.println("hi am here post");
		//super.doPost(request, response);
		
	}
	
	public void checkFileChangeOrNot(){
		
		boolean useClasspath = false;

try {
			System.out.println("the value of the arg is ");
			String[] anArray;  
			anArray = new String[10];
			anArray[0] = "Example.java";
			
			useClasspath = Boolean.valueOf(anArray[0]).booleanValue();
		    //useClasspath = Boolean.valueOf(args[0]).booleanValue();
		}
		catch (Exception e) {
			System.out.println("There is some exception and going to exit");
		    System.out.println("Usage: java Example <true|false>");
		    e.printStackTrace();
		    System.exit(1);
		}

// Example ex = new Example(useClasspath);
	        System.out.println("no am going to terminate the program ");
	        while(true){
	        	try {
					Thread.sleep(60000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
	        }
	        }

private static final String PROPERTIES_FILE = "f:/config.properties";

private boolean useClasspath;
    private long checkPeriod;
    private String cssFileName;

public long getCheckPeriod() {
    	System.out.println("getCheckPeriod");
        return checkPeriod;
    }

public synchronized void setCheckPeriod(long period) {
        log("Setting checkPeriod: " + period);
        checkPeriod = period;
	try {
	    FileMonitor.getInstance().addFileChangeListener(this, 
							PROPERTIES_FILE, 
							checkPeriod);
	}
	catch (FileNotFoundException e) {
	    e.printStackTrace();
	}
    }

public String getcssFileName() {
        return cssFileName;
    }

private synchronized void setcssFileName(String email) {
        log("Setting emailAddress: " + email);
        cssFileName = email;
    }

private void reloadProperties() {
    	System.out.println("reloadProperties()");
	Properties props = new Properties();
        InputStream in;

try {
            if (useClasspath) {
	        in = getClass().getClassLoader().getResourceAsStream(PROPERTIES_FILE);
	    }
	    else {
	        in = new FileInputStream(PROPERTIES_FILE);
	    }

props.load(in);
	    in.close();
	}
	catch (IOException e) {
	    e.printStackTrace();
	}

setCheckPeriod(Long.parseLong(props.getProperty("checkPeriod")));
	setcssFileName(props.getProperty("cssFileName"));
	//setLogLevel(Integer.parseInt(props.getProperty("logLevel")));
    }

public void fileChanged(String fileName) {
    	System.out.println("fileChanged(String fileName)");
        reloadProperties();
        System.out.println("We are going to redirect to main index.jsp");
        HttpServletResponse response = null ;
        try {
			response.sendRedirect("index.jsp");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
        
    }

public void log(String s) {
        System.out.println(s);
    }

}

3. FileChangeListener.java

package test;

public interface FileChangeListener {
    /** Invoked when a file changes.   
     * @param fileName name of changed file.
     */
    public void fileChanged(String fileName);
}

the following files are placed in the drive f:

4.configuration file config.properties

# Sample properties
checkPeriod=30
cssFileName=f:/style1.css

5. style sheet style1.css

root {
 
  display: block;
 
  font-size: 4px;
 
  font-style: italic;
 
  font-weight: normal;
 
  font-variant: normal;
 
  color: green;
 
  background-color: #ffffcc;
 
  background-attachment: none;
 
  font-family: Georgia,'Times New Roman',times,serif;
 
  }

6.style2.css same as style1.css with color  as red

please help me in that

anitha meena wrote:I have write and collect some code from the net but am getting some error

I anxiously await the details of the error.

Hi thanks alot for the reply ,

once you run the application i mean after opening the web page
http://localhost:8080/JSP-Listener-File/index.jsp

after doing that , open the configuratin file
config.properties and make a change to the property
cssFileName=style2.css
(if it is style1.css change it style2.css and vice versa)

save the changes , once you did this you ll see the error

It would be better if you posted the relevant parts of the error message here.
You're more likely to get useful help here if you can communicate the problem without requiring users to to test your application on another server.

Crossposted: http://forums.sun.com/thread.jspa?threadID=5358888
Please read this: http://faq.javaranch.com/java/BeForthrightWhenCrossPostingToOtherSites

Hi Thanks alot for the advise ,

I am really gaining knowledge from such replies , i ll try to fix the issues and let you know if i face any problem

Thanking you again