PrintServiceLookup.lookup in Tomcat

Question

Hi Forum,
How could I get javax.print.PrintServiceLookup.lookupPrintServices(null,null) to return the current available services while the program that uses lookupPrintServices is running? In a tomcat servlet, I use the lookupPrintServices(..) to get a list of the printer services available. The class works well and returns the
list but if I install a new printer, the servlet does not list the newly installed service until I restart Tomcat.
Is there a way to unload and reload the PrintServiceLookup class and then call PrintServiceLookup.lookupPrintServices?
It appears that the lookupPrintServices(..) returns the list of services that was available when the instance of the virtual machine was started. Hence, while the instance is running, it allways returns the same list of
services. If I run a program that lists the services and then exits, the program lists the newly added printer on re-run. But if the program never exits (it runs in a loop, re-listing the services every so often), and I add
a new printer while the program is running, the newly added printer is not listed until I terminate the pogram and re-start it.
Thanks in advance for your response

Answer 1

Thank for your response,
It appears that there is a bug in the JDK. A bug reported against the SUN JDK for this problem and it seeems that the bug has not been resolved yet.
A ling to the bug: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4744405
A brief description of the reported bug:
Bug ID: 4744405
Votes 17
Synopsis RFE: lookupPrintServices() to refresh the printers list dynamically
Category java:classes_2d
Reported Against 1.4 , 1.4.1
Release Fixed
State In progress, request for enhancement
Related Bugs 5028849 , 5033703
Submit Date 10-SEP-2002
Description *This also happened on Windows platform.
java version "1.4.1-rc"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.1-rc-b19)
Java HotSpot(TM) Client VM (build 1.4.1-rc-b19, mixed mode)
When invoke method lookupPrintServices() on class PrinterJob or PrintServiceLookup, the printers list can not refreshed when adding or deleting printers dynamically.
Steps to follow to reproduce the problem:
1. Compile and run the included test case
2. The print dialog shows up and avaible printers information is printed out on screen. Click "cancel" to dismiss the dialog. The test case is pending.
3. Use Printer Selector Tool to add a new printer into selected printers list and save changes.
4. Back to the terminal that run the test case an click "enter" button to continue. Then a new thread will be created to invoke the lookupPrintServices() and pop up the print dialog again.
5. The screen output shows that invoking lookupPrintServices() doesn't reflect the newly added printer information, neither does the print dialog.
//-------- source code begin-----------//
import java.awt.print.*;
import javax.print.*;
public class MTPrinterTest extends Thread {
public static void main(String[] args) {
MTPrinterTest t1 = new MTPrinterTest();
t1.start();
try {
System.in.read();
} catch (Exception e){}
MTPrinterTest t2 = new MTPrinterTest();
t2.start();
public void run() {
PrinterJob printerJob;
PrintService[] printServices;
printerJob = PrinterJob.getPrinterJob();
printServices = printerJob.lookupPrintServices();
System.out.println("Number of servies found: " + printServices.length);
for (int i =0; i< printServices.length; i++)
System.out.println("--> Available Printer " + i + ": " + printServices);
printerJob.printDialog();
//-------- source code end ----------//
Work Around Exit the current running application and run it again, then the printers list get refreshed. Seems the running JVM can not get updated printer information