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8263311: Watch registry changes for remote printers update instead of polling

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Reviewed-by: psadhukhan, serb
This commit is contained in:
Alexey Ivanov 2021-03-18 13:26:22 +00:00
parent 3f31a6baa9
commit a85dc557b3
3 changed files with 49 additions and 176 deletions
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112
src/java.desktop/windows/classes/sun/print/PrintServiceLookupProvider.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -26,8 +26,6 @@
package sun.print;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import javax.print.DocFlavor;
import javax.print.MultiDocPrintService;
@ -50,31 +48,7 @@ public class PrintServiceLookupProvider extends PrintServiceLookup {
private String[] printers; /* excludes the default printer */
private PrintService[] printServices; /* includes the default printer */
private static final int DEFAULT_REFRESH_TIME = 240; // 4 minutes
private static final int MINIMUM_REFRESH_TIME = 120; // 2 minutes
private static final boolean pollServices;
private static final int refreshTime;
static {
/* The system property "sun.java2d.print.polling"
* can be used to force the printing code to poll or not poll
* for PrintServices.
*/
String pollStr = java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction("sun.java2d.print.polling"));
pollServices = !("false".equalsIgnoreCase(pollStr));
/* The system property "sun.java2d.print.minRefreshTime"
* can be used to specify minimum refresh time (in seconds)
* for polling PrintServices. The default is 240.
*/
String refreshTimeStr = java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction(
"sun.java2d.print.minRefreshTime"));
refreshTime = (refreshTimeStr != null)
? getRefreshTime(refreshTimeStr)
: DEFAULT_REFRESH_TIME;
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<Void>() {
public Void run() {
@ -84,17 +58,6 @@ public class PrintServiceLookupProvider extends PrintServiceLookup {
});
}
private static int getRefreshTime(final String refreshTimeStr) {
try {
int minRefreshTime = Integer.parseInt(refreshTimeStr);
return (minRefreshTime < MINIMUM_REFRESH_TIME)
? MINIMUM_REFRESH_TIME
: minRefreshTime;
} catch (NumberFormatException e) {
return DEFAULT_REFRESH_TIME;
}
}
/* The singleton win32 print lookup service.
* Code that is aware of this field and wants to use it must first
* see if its null, and if so instantiate it by calling a method such as
@ -126,13 +89,11 @@ public class PrintServiceLookupProvider extends PrintServiceLookup {
thr.setDaemon(true);
thr.start();
if (pollServices) {
// start the remote printer listener thread
Thread remThr = new Thread(null, new RemotePrinterChangeListener(),
"RemotePrinterListener", 0, false);
remThr.setDaemon(true);
remThr.start();
}
// start the remote printer listener thread
Thread remThr = new Thread(null, new RemotePrinterChangeListener(),
"RemotePrinterListener", 0, false);
remThr.setDaemon(true);
remThr.start();
} /* else condition ought to never happen! */
}
@ -356,70 +317,15 @@ public class PrintServiceLookupProvider extends PrintServiceLookup {
}
}
/* Windows provides *PrinterChangeNotification* functions that provides
information about printer status changes of the local printers but not
network printers.
Alternatively, Windows provides a way through which one can get the
network printer status changes by using WMI, RegistryKeyChange combination,
which is a slightly complex mechanism.
The Windows WMI offers an async and sync method to read through registry
via the WQL query. The async method is considered dangerous as it leaves
open a channel until we close it. But the async method has the advantage of
being notified of a change in registry by calling callback without polling for it.
The sync method uses the polling mechanism to notify.
RegistryValueChange cannot be used in combination with WMI to get registry
value change notification because of an error that may be generated because the
scope of the query would be too big to handle(at times).
Hence an alternative mechanism is chosen via the EnumPrinters by polling for the
count of printer status changes(add\remove) and based on it update the printers
list.
*/
class RemotePrinterChangeListener implements Comparator<String>, Runnable {
RemotePrinterChangeListener() {
}
@Override
public int compare(String o1, String o2) {
return ((o1 == null)
? ((o2 == null) ? 0 : 1)
: ((o2 == null) ? -1 : o1.compareTo(o2)));
}
private final class RemotePrinterChangeListener implements Runnable {
@Override
public void run() {
// Init the list of remote printers
String[] prevRemotePrinters = getRemotePrintersNames();
if (prevRemotePrinters != null) {
Arrays.sort(prevRemotePrinters, this);
}
while (true) {
try {
Thread.sleep(refreshTime * 1000);
} catch (InterruptedException e) {
break;
}
String[] currentRemotePrinters = getRemotePrintersNames();
if (currentRemotePrinters != null) {
Arrays.sort(currentRemotePrinters, this);
}
if (!Arrays.equals(prevRemotePrinters, currentRemotePrinters)) {
// The list of remote printers got updated,
// so update the cached list printers which
// includes both local and network printers
refreshServices();
// store the current data for next comparison
prevRemotePrinters = currentRemotePrinters;
}
}
notifyRemotePrinterChange(); // busy loop in the native code
}
}
private native String getDefaultPrinterName();
private native String[] getAllPrinterNames();
private native void notifyLocalPrinterChange();
private native String[] getRemotePrintersNames();
private native void notifyRemotePrinterChange();
}