Applet Servlet Communication

[hareesh Puthala]

Can you please help me out in this issue.


Our requirement is that Applet (PrintApplet in our case)just needs to send a value(jsp page name)
to a servlet(AppletListenerServlet in our case) and that servlet needs to redirect it to the page which is sent by the Applet.

My applet request is able to reach the servlet and i am able to get the jsp page value in the servlet,but the servlet is not able to forward the request to that jsp instead of that the same applet page is displayed.

Servlet is not able to forward the request.

Could you please please please help me out in this ....

Many many thanks in advance.

[Ulf Dittmer]

So the applet calls the servlet using java.net.URLConnection or something similar? If so, then the servlet can't cause the applet page to redirect to another page - the applet needs to do that by calling AppletContext.showDocument.

[hareesh Puthala]

Ulf Dittmer wrote:So the applet calls the servlet using java.net.URLConnection or something similar? If so, then the servlet can't cause the applet page to redirect to another page - the applet needs to do that by calling AppletContext.showDocument.

Iam getting this Exception while iam trying to call the method 'this.getAppletContext().showDocument(url)';


Exception in thread "AWT-EventQueue-2" java.lang.NullPointerException
at sun.plugin2.main.client.MessagePassingExecutionContext.showDocument(Unknown Source)
at sun.plugin2.main.client.MessagePassingExecutionContext.showDocument(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletContextImpl.showDocument(Unknown Source)
at PrintApplet.actionPerformed(PrintApplet.java:105)
at java.awt.Button.processActionEvent(Unknown Source)
at java.awt.Button.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

But the appletcontext object is not null which i found on the java console.

Thanks in advance.

[Ulf Dittmer]

The NPE occurs in the showDocument method, so the AppletContext is obviously not null.

What's the value of the URL you're passing in? In which browser does this happen?

[hareesh Puthala]

Ulf Dittmer wrote:The NPE occurs in the showDocument method, so the AppletContext is obviously not null.

What's the value of the URL you're passing in? In which browser does this happen?

Value of the URL is: http://10.16.1.43:8090/collectionpak/pages/consumerService.jsp

And the browser is IE 6.0

[hareesh Puthala]

hareesh Puthala wrote:

Ulf Dittmer wrote:The NPE occurs in the showDocument method, so the AppletContext is obviously not null.

What's the value of the URL you're passing in? In which browser does this happen?

Value of the URL is: http://10.16.1.43:8090/collectionpak/pages/consumerService.jsp

And the browser is IE 6.0

Here is my code:

import java.applet.Applet;
import java.awt.Button;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedWriter;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.net.URL;
import java.util.Hashtable;

import javax.print.Doc;
import javax.print.DocFlavor;
import javax.print.DocPrintJob;
import javax.print.PrintService;
import javax.print.PrintServiceLookup;

public class PrintApplet extends Applet implements ActionListener {

	private static final long serialVersionUID = 1L;

	String flag = "";

	Button btnCreateFile_;

	Hashtable headers = null;

	String applFees = "", secDeposit = "", devCharges = "",
			serviceLineCharges = "", fileName = "", eroname = "", uscno2 = "",
			RCCODE = "", cahsInWords = "", modeofrec1 = "", ddcheckno1 = "",
			dddate = "", nameofbank1 = "", cashreceived2 = "", eroc2 = "",
			paac2 = "", acd2 = "", collect2 = "", rcfee3 = "", currentpr = "",
			finalprno2 = "", category = "", arrears4 = "", currentdemand2 = "",
			dt2 = "", uscno3 = "", name4 = "", arrears2 = "", rcname = "",
			section2 = "", remarks = "", miscFlag = "", stringurl = "",
			JSESSIONID = "";

	String eroName = "";

	String misc = "";

	String msg_ = "Before printing";

	public void init() {

		fileName = getParameter("fileName");
		eroname = getParameter("eroname");
		uscno2 = getParameter("uscno2");
		RCCODE = getParameter("RCCODE");
		cahsInWords = getParameter("cashInWords");
		modeofrec1 = getParameter("modeofrec1");
		ddcheckno1 = getParameter("ddcheckno1");
		dddate = getParameter("dddate");
		nameofbank1 = getParameter("nameofbank1");
		cashreceived2 = getParameter("cashreceived2");
		eroc2 = getParameter("eroc2");
		acd2 = getParameter("acd2");
		rcfee3 = getParameter("rcfee3");
		currentpr = getParameter("currentpr");
		finalprno2 = getParameter("finalprno2");
		category = getParameter("category");
		arrears4 = getParameter("arrears4");
		currentdemand2 = getParameter("currentdemand2");
		dt2 = getParameter("dt2");
		uscno3 = getParameter("uscno3");
		name4 = getParameter("name4");
		rcname = getParameter("rcname");
		section2 = getParameter("section");
		misc = getParameter("misc");
		remarks = getParameter("remarks");
		miscFlag = getParameter("miscFlag");
		applFees = getParameter("applFees");
		secDeposit = getParameter("devCharges");
		devCharges = getParameter("secDeposit");
		serviceLineCharges = getParameter("serviceLineCharges");
		stringurl = getParameter("stringurl");
		btnCreateFile_ = new Button("Print");
		headers = new Hashtable();
		add(btnCreateFile_);
		btnCreateFile_.addActionListener(this);

	}

	public void actionPerformed(ActionEvent ae) {
		String str = ae.getActionCommand();

		if (str.equals("Print")) {
			createFile();
			btnCreateFile_.setVisible(false);
			repaint();
		}
		try {
			String urlstr = getCodeBase().toString();
			urlstr = urlstr.concat(stringurl);
			URL url = new URL(stringurl);
			System.out.println("urlstr:" + urlstr);
			System.out.println("APPLCONTEXT:" + this.getAppletContext());
			this.getAppletContext().showDocument(url);
		} catch (Exception e) {

		}
	}

}

I am performing spme business logic in the create method(It creates a text file in the local file system and drives the default printer and prin ts the text file.)


Please look into this ...
Thanks a lot for helping me.

[hareesh Puthala]

Now it is not even calling the appletcontext.showDocument().

Why this is happening?

[Ulf Dittmer]

This is never a good idea:

} catch (Exception e) {  
}

You need to do proper error handling. At least put something like "e.printStackTrace()" so that you know what happened.

Also, does "urlstr" have any meaning? It is not used in the code.

[hareesh Puthala]

Thanks a lot Ulf Dittmer..

It has done the trick.

Once again thank you very much......