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Rendering big Post Script file with Ghost4J in Java

i made a Java application whose purpose is to offer a Print Preview for PS files.
My program uses Ghostscript and Ghost4J to load the Post Script file and produces a list of Images (one for each page) using the SimpleRenderer.render method. Then using a simple JList i show only the image corresponding to the page the user selected in JList.
This worked fine until a really big PS file occurred, causing an OutOfMemoryError when executing the code
PSDocument pdocument = new PSDocument(new File(filename));
I know that is possibile to read a file a little at a time using InputStreams, the problem is that i can't think of a way to connect the bytes that i read with the actual pages of the document.
Example, i tried to read from PS file 100 MB at a time
int buffer_size = 100000000;
byte[] buffer = new byte[buffer_size];
FileInputStream partial = new FileInputStream(filename);
partial.read(buffer, 0, buffer_size);
document.load(new ByteArrayInputStream(buffer));
SimpleRenderer renderer = new SimpleRenderer();
//how many pages do i have to read?
List<Image> images = renderer.render(document, firstpage ??, lastpage ??);
Am i missing some Ghost4J functionality to read partially a file?
Or has someone other suggestions / approaches about how to solve this problem in different ways?
I am really struggling

I found out I can use Ghost4J Core API to retrieve from a Post Script file a reduced set of pages as Images.
Ghostscript gs = Ghostscript.getInstance();
String[] gsArgs = new String[9];
gsArgs[0] = "-dQUIET";
gsArgs[1] = "-dNOPAUSE";
gsArgs[2] = "-dBATCH";
gsArgs[3] = "-dSAFER";
gsArgs[4] = "-sDEVICE=display";
gsArgs[5] = "-sDisplayHandle=0";
gsArgs[6] = "-dDisplayFormat=16#804";
gsArgs[7] = "-sPageList="+firstPage+"-"+lastPage;
gsArgs[8] = "-f"+filename;
//create display callback (capture display output pages as images)
ImageWriterDisplayCallback displayCallback = new ImageWriterDisplayCallback();
//set display callback
gs.setDisplayCallback(displayCallback);
//run PostScript (also works with PDF) and exit interpreter
try {
gs.initialize(gsArgs);
gs.exit();
Ghostscript.deleteInstance();
} catch (GhostscriptException e) {
System.out.println("ERROR: " + e.getMessage());
e.printStackTrace();
}
return displayCallback.getImages(); //return List<Images>
This solve the problem of rendering page as images in the preview.
However, i could not find a way to use Ghost4J to know total number of pages of PS file (in case the file is too big for opening it with Document.load()).
So, i am still here needing some help

How to get the opened document using UNO?

I'm writing an add-on that opens a dialog and I need to access the currently opened text document but I don't know how get it.
I'm using the OpenOffice plug-in in NetBeans and I started from an Add-on project. It created a class that gives me a XComponentContext instance but I don't know how to use it to get a OfficeDocument instance of the current document.
I've been googling for some time and I can't find any example that uses an existing, opened, document. They all start from a new document or a document that is loaded first so they have an URL for it.
I gave it a try based on the OpenOffice wiki (https://wiki.openoffice.org/wiki/API/Samples/Java/Office/DocumentHandling) and this is what I came up with:
private OfficeDocument getDocument() {
if (this.officeDocument == null) {
try {
// this causes the error
XMultiComponentFactory xMultiComponentFactory = this.xComponentContext.getServiceManager();
Object oDesktop = xMultiComponentFactory.createInstanceWithContext("com.sun.star.frame.Desktop", this.xComponentContext);
XComponentLoader xComponentLoader = UnoRuntime.queryInterface(XComponentLoader.class, oDesktop);
String url = "private:factory/swriter";
String targetFrameName = "_self";
int searchFlags = FrameSearchFlag.SELF;
PropertyValue[] propertyValues = new PropertyValue[1];
propertyValues[0] = new PropertyValue();
propertyValues[0].Name = "Hidden";
propertyValues[0].Value = Boolean.TRUE;
XComponent xComponent = xComponentLoader.loadComponentFromURL(url, targetFrameName, searchFlags, propertyValues);
XModel xModel = UnoRuntime.queryInterface(XModel.class, xComponent);
this.officeDocument = new OfficeDocument(xModel);
} catch (com.sun.star.uno.Exception ex) {
throw new RuntimeException(ex);
}
}
return this.officeDocument;
}
But there is something strange going on. Just having this method in my class, even if it's never been called anywhere, causes an error when adding the add-on.
(com.sun.star.depoyment.DeploymentDescription){{ Message = "Error during activation of: VaphAddOn.jar", Context = (com.sun.star.uno.XInterface) #6ce03e0 }, Cause = (any) {(com.sun.star.registry.CannotRegisterImplementationException){{ Message = "", Context = (com.sun.star.uno.XInterface) #0 }}}}
It seems this line causes the error:
XMultiComponentFactory xMultiComponentFactory = this.xComponentContext.getServiceManager();
I have no idea how to preceed.
I posted this question on the OpenOffice forum but I haven't got a response there. I'm trying my luck here now.

Use this in your code to get the current document:
import com.sun.star.frame.XDesktop;
...
XDesktop xDesktop = (XDesktop) UnoRuntime.queryInterface(XDesktop.class, oDesktop);
XComponent xComponent = xDesktop.getCurrentComponent();
I opened the BookmarkInsertion sample in NetBeans and added this code to use the current document instead of loading a new document.
As far as the error, there may be a problem with how it is getting built. A couple of things to check:
Does the Office SDK version match the Office version? Check version number and whether it's 32- or 64-bit.
Make sure that 4 .jar files (juh.jar, jurt.jar, unoil.jar, ridl.jar) are shown under Libraries in NetBeans, because they need to be included along with the add-on.
If you get frustrated with trying to get the build set up correctly, then you might find it easier to use python, since it doesn't need to be compiled. Also python does not require queryInterface().

Zxing qr scanning blackberry crash

I am implementing a QR code scanner for blackberry devices and I am using ZXing libraries to do so. This is for os 6+ by the way. The problem I am having is that sometimes, only sometimes, when the camera opens up to prepare scanning, the device will freeze and do a full reboot...
Otherwise it works most of the time, I am able to scan and decode the qr codes etc. However is just seems like it occasionally feels like crashing for no reason. I do not know if it is something with the camera or something in my code, but I will provide the code.
public void scanBarcode() {
// First we create a hashtable to hold all of the hints that we can
// give the API about how we want to scan a barcode to improve speed
// and accuracy.
Hashtable hints = new Hashtable();
// The first thing going in is a list of formats. We could look for
// more than one at a time, but it's much slower.
Vector formats = new Vector();
formats.addElement(BarcodeFormat.QR_CODE);
hints.put(DecodeHintType.POSSIBLE_FORMATS, formats);
// We will also use the "TRY_HARDER" flag to make sure we get an
// accurate scan
hints.put(DecodeHintType.TRY_HARDER, Boolean.TRUE);
// We create a new decoder using those hints
BarcodeDecoder decoder = new BarcodeDecoder(hints);
// Finally we can create the actual scanner with a decoder and a
// listener that will handle the data stored in the barcode. We put
// that in our view screen to handle the display.
try {
_scanner = new BarcodeScanner(decoder, new MyBarcodeDecoderListener());
_barcodeScreen = new MyBarcodeScannerViewScreen(_scanner);
} catch (Exception e) {
return;
}
// If we get here, all the barcode scanning infrastructure should be set
// up, so all we have to do is start the scan and display the viewfinder
try {
_scanner.stopScan();
_scanner.getPlayer().start();
_scanner.startScan();
UiApplication.getUiApplication().pushScreen(_barcodeScreen);
} catch (Exception e) {
}
}
/***
* MyBarcodeDecoderListener
* <p>
* This BarcodeDecoverListener implementation tries to open any data encoded
* in a barcode in the browser.
*
* #author PBernhardt
*
**/
private class MyBarcodeDecoderListener implements BarcodeDecoderListener {
public void barcodeDecoded(final String rawText) {
//UiApplication.getUiApplication().popScreen(UiApplication.getUiApplication().getActiveScreen());
UtilityDecoder.saveToHistory(rawText);
try {
UtilityDecoder.distributeBarcode(rawText);
} catch (PIMException e) {
}
}
}
I basically call scanBarcode() when I click on a button on a toolbar.
Can anyone tell me if my code is the problem, or the device, or something else? Thanks in advance for any help provided!

Try this link:
Scan Any Type of Barcode Image which Supports Blackberry
See this forun link and see the discussions of that link. Surely, you will get overall concept of barcode scanning and you will also get the Implemention of QRCode in version 5.0
Any type of Barcode scaning in 5.0

Remember the values entered on standalone app on the client side

We have a standalone java swing app, in which the user can print something that he drew, on a printer by giving its IP.
Now the requirement is that the app needs to remember the ip that was given the last time by this user.
What I could think of till now is (a brute one though) - keep a log file kind of storage on the client machine, and that everytime the app comes up it reads the last submitted one.
Any suggestions would be helpful.
Thanks in advance.

Here's a tutorial on using the Java Preferences API to achieve what you want.
From the article:
The Java Preferences API provides a
systematic way to handle user and
system preference and configuration
data, e.g. to save user settings,
remember the last value of a field
etc.
I would use this approach over writing any data out explicitly to a file because its platform agnostic.

More or Less that's it. Still you can review the source code for HistoryTextField component of jEdit.
http://www.jedit.org/api/org/gjt/sp/jedit/gui/HistoryTextField.html
A Sample from jEdit source:
public boolean save(Map<String, HistoryModel> models)
{
Log.log(Log.MESSAGE,HistoryModel.class,"Saving history");
File file1 = new File(MiscUtilities.constructPath(
jEdit.getSettingsDirectory(), "#history#save#"));
File file2 = new File(MiscUtilities.constructPath(
jEdit.getSettingsDirectory(), "history"));
if(file2.exists() && file2.lastModified() != historyModTime)
{
Log.log(Log.WARNING,HistoryModel.class,file2
+ " changed on disk; will not save history");
return false;
}
jEdit.backupSettingsFile(file2);
String lineSep = System.getProperty("line.separator");
BufferedWriter out = null;
try
{
out = new BufferedWriter(new OutputStreamWriter(
new FileOutputStream(file1), "UTF-8"));
if(models != null)
{
Collection<HistoryModel> values = models.values();
for (HistoryModel model : values)
{
if(model.getSize() == 0)
continue;
out.write('[');
out.write(StandardUtilities.charsToEscapes(
model.getName(),TO_ESCAPE));
out.write(']');
out.write(lineSep);
for(int i = 0; i < model.getSize(); i++)
{
out.write(StandardUtilities.charsToEscapes(
model.getItem(i),
TO_ESCAPE));
out.write(lineSep);
}
}
}
out.close();
/* to avoid data loss, only do this if the above
* completed successfully */
file2.delete();
file1.renameTo(file2);
}
catch(IOException io)
{
Log.log(Log.ERROR,HistoryModel.class,io);
}
finally
{
IOUtilities.closeQuietly(out);
}
historyModTime = file2.lastModified();
return true;
}

Since it is a Swing app., you might launch it using Java Web Start then persist the data using the PersistenceService. Here is a demo. of the PersistenceService.

i dont really recommend this, but you could use the registry also.

Is there a good reference for using OLE Automation (from Java)?

I am trying to communicate with Excel from a Java/SWT application. I have been able to open a worksheet, open a file and save it but that's about it.
Can anyone point me to some documentation/examples for this? I especially need to know which commands are available. I did try to record macros to inspect. This was useful but did not give me everything I wanted.
This is a sample of what I have been trying so far:
private static OleAutomation openFile(
OleAutomation automation, String fileName) {
Variant workbooks = automation.getProperty(0x0000023c);// get User
// Defined
// Workbooks
Variant[] arguments = new Variant[1];
arguments[0] = new Variant(fileName);
System.out.println("workbooks::\t" + workbooks);
IDispatch p1 = workbooks.getDispatch();
int[] rgdispid = workbooks.getAutomation().getIDsOfNames(new String[] { "Open" });
int dispIdMember = rgdispid[0];
Variant workbook = workbooks.getAutomation().invoke(dispIdMember, arguments);
System.out.println("Opened the Work Book");
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
int id = workbook.getAutomation().getIDsOfNames(new String[] { "ActiveSheet" })[0];
System.out.println(id);
Variant sheet = workbook.getAutomation().getProperty(id);
OleAutomation sheetAutomation = sheet.getAutomation();
return (sheetAutomation);
}

Use VBA help MSOffice. Also you can use Object Browser in Office's VB editor.

Not a documentation, but since you asked about the available commands via automation: have you tried the OLE/COM Object viewer that comes with the Windows 2000 resource kit? Download here.