Error: Object reference not set to an instance of an object…Exception object : System.NullReferenceException: Object reference not set to an instance of an object.
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at Aspose.Pdf.Document.#=zi4GC8wjiZUZd(Stream #=z4pqNpB4=, SaveOptions #=zi4O4HzyLOJ$X)
at Aspose.Pdf.Document.Save(Stream output)
- We are trying to replace text in particular position.
- It is working in onprem services and local windows machine.
- We are migrating our onprem service to GCP when we deploy our code to GCP in which we have GKE linux based instance, Its throwing above exception.
- We using Aspose.PDF 23.9 Latest version
- The sample pdf file here
sample-pdf.pdf (59.0 KB)
here is the C# code in .net core 6 we using
Code Snippet:
var transformedFileInBytes = TransformDocumentUsingAspose_test(pdfStream, "Signature", "Venkateswarlu123");
private byte[] TransformDocumentUsingAspose_test(Stream stream, string searchText, string textToReplace)
{
byte[] transformedFileInBytes = null;
Document pdfDocument = new Document(stream); //Converting PDF Document Stream to Aspose.PDF.Document
Page searchTextMatchedPage = null; //Aspose.PDF.Page
var textFragmentAbsorber = new TextFragmentAbsorber(searchText); //Aspose.PDF.Text.TextFragmentAbsorber
Position position = null;
foreach (Page page in pdfDocument.Pages)
{
page.Accept(textFragmentAbsorber);
position = textFragmentAbsorber.TextFragments?.ConvertToGenericList<TextFragment>()?.Select(x => x?.Position)?.FirstOrDefault();
if (position == null) continue;
searchTextMatchedPage = page;
break;
}
if (position == null)
{
throw new KeyNotFoundException($"Document doesn't contain {searchText} text");
}
var xIndent = position?.XIndent ?? 20;
var yIndent = position?.YIndent ?? 220;
var searchTextMatchedPosition = new Position(xIndent, yIndent + 20);
var textFragment = new TextFragment(textToReplace)
{
Position = searchTextMatchedPosition
};
textFragment.TextState.FontSize = 12;
FontRepository.Sources.Add(new FolderFontSource(@"TimesNewRoman")); //To resolve Font Not Found exception on GCP GKE Linux instance
var font = FontRepository.FindFont("TimesNewRoman");
textFragment.TextState.Font = FontRepository.FindFont("TimesNewRoman");
textFragment.TextState.BackgroundColor = Color.FromRgb(System.Drawing.Color.LightGray);
textFragment.TextState.ForegroundColor = Color.FromRgb(System.Drawing.Color.Black);
// Create TextBuilder object
var textBuilder = new TextBuilder(searchTextMatchedPage);
textBuilder.AppendText(textFragment);
using (var memoryStream = new MemoryStream())
{
pdfDocument.Save(memoryStream);
transformedFileInBytes = memoryStream.ToArray();
}
return transformedFileInBytes;
}@sergei.shibanov Here is the method implementation
public static IList<TList> ConvertToGenericList<TList>(this IEnumerable sourceList)
{
try
{
return sourceList.Cast<TList>().ToList();
}
catch (NullReferenceException ex)
{
throw ex;
}
catch (InvalidCastException innerException)
{
throw new InvalidCastException($"All source in sourceList must be of type: {typeof(TList)}", innerException);
}
}@venkateswarlu123
I tried to reproduce this exception, but it worked for me.
Perhaps the reason is that the environment you are using does not have any fonts. I used the operator at the beginning of the code
FontRepository.Sources.Add(new FolderFontSource("Fonts"));
There were the following files in the Fonts folder. image.png (3.3 KB)
@sergei.shibanov Can you please confirm
- did you use linux machine ?
- we getting this issue ony when deployed to Google cloud GKE using linux base image. its working in onprem.
are you trying the same to reproduce the issue?
We also added this
FontRepository.Sources.Add(new FolderFontSource("Fonts"));
and font also getting read without any errors.
@venkateswarlu123
I don’t have GKE and I tested it in Visual Studio using docker desktop (for testing in a Linux environment). The most common problem in this case is the lack of any fonts. Unfortunately, this often throws a NullReferenceException or something else instead of indicating the absence of fonts. The stack trace you provided also indicates problems when opening the font. This feature is mentioned in How to Install Aspose.PDF for .NET|Aspose.PDF for .NET in the section Working with .NET Core DLLs in Non-Windows Environment.
When checking myself, I did
image.png (5.5 KB)
In addition, when working on Linux systems, I recommend using the Aspose.Pdf.Drawing library, which in this case is more reliable and does not require installation libgdiplus package (since it does not use libgdiplus)
Hi @sergei.shibanov
We have migrated that piece of code to another repo which is also hosted in GCP GKE
but using .net core 3.1 . There also we got Font Not Found exception, then we downloaded fonts manually to a folder and added that folder to Font Sources. After that it started working.
But this is not a permanent fix in our case. All of our code base will use .Net 6 going forward. Please get it fixed for .Net 6 deployed to GKE as soon as possible. If it is already fixed please help us to fix it.
at this link I posted a project with the code you provided under .Net 6 working in Docker Linux container.