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Converting Documents in AWS
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If you’re building cloud-native applications on AWS and require robust PDF generation, manipulation, or conversion capabilities, integrating Aspose.PDF for .NET into AWS Lambda functions offers a powerful and scalable solution. This approach allows you to leverage the extensive features of Aspose.PDF within the serverless environment of AWS, potentially integrating with other services like S3 for storage.
This article guides you through setting up and running Aspose.PDF for .NET in AWS Lambda, covering basic PDF creation and addressing common challenges like font management in the cloud.
Prerequisites
- Active AWS Account. Required for creating and deploying Lambda functions. If you don’t have one, sign up at aws.amazon.com.
- Visual Studio 2017, 2019, or 2022 with the AWS Toolkit for Visual Studio installed. This simplifies project creation, deployment, and testing.
Run an Aspose.PDF for .NET application in AWS Lambda
Follow these steps to create a simple Lambda function that generates a PDF document using Aspose.PDF and saves it to Amazon S3:
- Create AWS Lambda Project. In Visual Studio, create a new project using the AWS Lambda Project (.NET Core - C#) template. Select the Empty Function blueprint when prompted. This provides a basic function structure.
- Add NuGet Packages. Right-click on your project in Solution Explorer, select “Manage NuGet Packages…”, and install the following:
Aspose.PDF. The core library for PDF manipulation.AWSSDK.S3. The AWS SDK for .NET library to interact with S3 storage.
- Implement the Lambda Function. Replace the contents of your function handler file (e.g.,
Function.cs) with the following code. This example creates a basic PDF document with text and saves it to an S3 bucket.
using System;
using System.IO;
using System.Threading.Tasks;
using Amazon.Lambda.Core;
using Amazon.S3;
using Amazon.S3.Model;
using Aspose.Pdf;
using Aspose.Pdf.Text;
// Assembly attribute to enable the Lambda function's JSON input to be converted into a .NET class.
[assembly: LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]
namespace TestAsposePdfLambda
{
public class Function
{
private IAmazonS3 S3Client { get; set; }
private const string BucketName = "your-s3-bucket-name";
/// <summary>
/// Default constructor. Initializes the S3 client.
/// </summary>
public Function()
{
S3Client = new AmazonS3Client();
// Consider setting the License here if needed, e.g., in a static constructor
Aspose.Pdf.License lic = new Aspose.Pdf.License();
// Assumes license file is an embedded resource
lic.SetLicense("Aspose.PDF.lic");
}
/// <summary>
/// Lambda function handler: Creates a PDF document and saves it to S3.
/// </summary>
public async Task<string> FunctionHandler(string input, ILambdaContext context)
{
context.Logger.LogLine($"Function processing input: {input}");
// Create PDF document
Document pdfDocument = new Document();
// Add a page
Page page = pdfDocument.Pages.Add();
// Add text elements
page.Paragraphs.Add(new TextFragment($"Hello {input} from Aspose.PDF!"));
page.Paragraphs.Add(new TextFragment($"You are running on: {System.Environment.OSVersion.VersionString}"));
// Save the PDF to a MemoryStream
using (MemoryStream ms = new MemoryStream())
{
// Aspose.PDF saves directly to PDF format
pdfDocument.Save(ms);
// Reset stream position for reading
ms.Position = 0;
// Upload the stream to S3
string outputKey = $"AP_out_{DateTime.UtcNow:yyyyMMddHHmmss}.pdf";
context.Logger.LogLine($"Attempting to upload {outputKey} to bucket {BucketName}");
bool putResult = await PutS3Object(BucketName, outputKey, ms, context);
return putResult ? $"OK - PDF saved as s3://{BucketName}/{outputKey}" : "FAILED to upload PDF to S3";
}
}
/// <summary>
/// Helper method to upload a stream to an S3 bucket.
/// </summary>
private async Task<bool> PutS3Object(string bucket, string key, Stream content, ILambdaContext context)
{
try
{
PutObjectRequest request = new PutObjectRequest
{
BucketName = bucket,
Key = key,
InputStream = content,
// Set appropriate content type
ContentType = "application/pdf"
};
var response = await S3Client.PutObjectAsync(request);
context.Logger.LogLine($"S3 PutObject Response: {response.HttpStatusCode}");
return response.HttpStatusCode == System.Net.HttpStatusCode.OK;
}
catch (AmazonS3Exception s3ex)
{
context.Logger.LogLine($"Error uploading to S3: {s3ex.Message} (AWS Request ID: {s3ex.RequestId}, Error Code: {s3ex.ErrorCode})");
return false;
}
catch (Exception ex)
{
context.Logger.LogLine($"General error during S3 upload: {ex.Message}");
return false;
}
}
}
}
- Deploy and Test
- Replace
"your-s3-bucket-name"in the code with the name of an S3 bucket you have write access to. - Right-click the project in Visual Studio and select Publish to AWS Lambda…. Follow the wizard to configure and deploy your function.
- Once deployed, you can invoke the function from Visual Studio’s AWS Explorer or the AWS Management Console. Pass any string as input.
- Check your S3 bucket for the generated PDF file (e.g.,
AP_out_... .pdf).
Potential Issue: Font availability
When you examine the generated PDF, you might notice that the text doesn’t use the standard fonts you’d expect (like Arial or Times New Roman). Instead, Aspose.PDF might use a fallback font. AWS Lambda execution environments are minimal Linux containers. They typically lack the common TrueType fonts found on Windows or desktop Linux distributions. When Aspose.PDF cannot find the specified or default fonts, it substitutes them with available fallback fonts to ensure the text is still rendered. This can affect the visual fidelity of your document.
How to Use Custom Fonts Stored in S3 with Aspose.PDF for .NET
To ensure your PDFs render with the correct fonts, you need to provide them to Aspose.PDF within the Lambda environment. Storing fonts in an S3 bucket is a flexible and common approach for cloud applications:
- Upload Fonts to S3. Create a folder (e.g.,
Fonts) in your S3 bucket and upload the necessary TrueType (.ttf) or OpenType (.otf) font files. For demonstration, you could use a freely available set like “Noto Sans”. - Load Fonts from S3 in Lambda. Modify your Lambda function to fetch these font files from S3 and register them with Aspose.PDF’s
FontRepository.
Here’s how you can adapt the previous Lambda function code:
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Amazon.Lambda.Core;
using Amazon.S3;
using Amazon.S3.Model;
using Aspose.Pdf;
using Aspose.Pdf.Text;
// Assembly attribute
[assembly: LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]
namespace TestAsposePdfLambda
{
public class Function
{
private IAmazonS3 S3Client { get; set; }
private const string BucketName = "your-s3-bucket-name"; // Replace with your bucket name
private const string FontsS3Folder = "Fonts/"; // Folder in your bucket containing .ttf/.otf files
private static bool _fontsLoaded = false; // Flag to load fonts only once per container instance
private static readonly object _fontLoadLock = new object(); // Lock for thread safety
/// <summary>
/// Static constructor: Ensures fonts are loaded when the class is first accessed
/// within a Lambda execution environment instance.
/// </summary>
static Function()
{
// Consider setting the License here if needed
Aspose.Pdf.License lic = new Aspose.Pdf.License();
lic.SetLicense("Aspose.PDF.lic");
}
/// <summary>
/// Default constructor. Initializes S3 client.
/// </summary>
public Function()
{
S3Client = new AmazonS3Client();
// Ensure fonts are loaded
EnsureFontsLoaded(S3Client, BucketName, FontsS3Folder);
}
/// <summary>
/// Lambda function handler: Creates a PDF with custom fonts loaded from S3.
/// </summary>
public async Task<string> FunctionHandler(string input, ILambdaContext context)
{
context.Logger.LogLine($"Function processing input: {input}");
// Ensure fonts loaded (important for warm starts)
EnsureFontsLoaded(S3Client, BucketName, FontsS3Folder, context);
// Create PDF document
Document pdfDocument = new Document();
// Add a page
Page page = pdfDocument.Pages.Add();
// Create TextFragment and specify the font
TextFragment titleFragment = new TextFragment($"Hello {input} from Aspose.PDF!");
// Attempt to find the font loaded from S3. Use the actual font name
titleFragment.TextState.Font = FontRepository.FindFont("Noto Sans");
// If the font wasn't found/loaded, FindFont might return a default/fallback font
titleFragment.TextState.FontSize = 14;
page.Paragraphs.Add(titleFragment);
TextFragment infoFragment = new TextFragment($"Running on: {System.Environment.OSVersion.VersionString}");
// Example using a specific style
infoFragment.TextState.Font = FontRepository.FindFont("Noto Sans Regular");
infoFragment.TextState.FontSize = 10;
page.Paragraphs.Add(infoFragment);
// Save PDF to stream
using (MemoryStream ms = new MemoryStream())
{
pdfDocument.Save(ms);
ms.Position = 0;
// Upload to S3
string outputKey = $"AP_Font_out_{DateTime.UtcNow:yyyyMMddHHmmss}.pdf";
context.Logger.LogLine($"Attempting to upload {outputKey} to bucket {BucketName}");
bool putResult = await PutS3Object(BucketName, outputKey, ms, context);
return putResult ? $"OK - PDF saved as s3://{BucketName}/{outputKey}" : "FAILED to upload PDF to S3";
}
}
/// <summary>
/// Loads fonts from S3 into Aspose.PDF's FontRepository if not already loaded.
/// </summary>
private void EnsureFontsLoaded(IAmazonS3 s3Client, string bucketName, string fontsFolderKey, ILambdaContext context = null)
{
// Prevent multiple threads/invocations trying to load simultaneously
lock (_fontLoadLock)
{
if (_fontsLoaded)
{
return;
}
context?.Logger.LogLine("Attempting to load fonts from S3...");
try
{
// Get font sources from S3
var fontSources = Task.Run(async () => await GetS3FontSources(s3Client, bucketName, fontsFolderKey, context)).Result;
if (fontSources.Any())
{
// Clear existing default sources (optional, ensures only S3 fonts are primary)
// FontRepository.Sources.Clear();
// Add the sources loaded from S3
FontRepository.Sources.AddRange(fontSources);
context?.Logger.LogLine($"Successfully loaded {fontSources.Count()} font sources from S3.");
_fontsLoaded = true;
}
else
{
context?.Logger.LogLine("No font sources found in S3 folder.");
// Set _fontsLoaded to true anyway to avoid retrying every invocation if folder is empty/missing
_fontsLoaded = true;
}
}
catch (AggregateException aggEx) when (aggEx.InnerException is AmazonS3Exception s3Ex)
{
context?.Logger.LogLine($"S3 Error loading fonts: {s3Ex.Message} (Request ID: {s3Ex.RequestId}, Error Code: {s3Ex.ErrorCode}) - Check bucket/folder name and permissions.");
// Avoid retrying constantly on permission errors
_fontsLoaded = true;
}
catch (Exception ex)
{
context?.Logger.LogLine($"Error loading fonts from S3: {ex.ToString()}");
// Decide if you want to retry or not. Setting _fontsLoaded = true prevents retries.
_fontsLoaded = true;
}
}
}
/// <summary>
/// Lists font files in an S3 folder and creates MemoryFontSource for each.
/// </summary>
private static async Task<List<MemoryFontSource>> GetS3FontSources(IAmazonS3 client, string bucketName, string fontsFolderKey, ILambdaContext context)
{
List<MemoryFontSource> fontSources = new List<MemoryFontSource>();
ListObjectsV2Request request = new ListObjectsV2Request()
{
BucketName = bucketName,
// e.g., "Fonts/"
Prefix = fontsFolderKey,
};
context?.Logger.LogLine($"Listing objects in {bucketName}/{fontsFolderKey}");
ListObjectsV2Response response;
do
{
// Requires s3:ListBucket permission on the bucket
response = await client.ListObjectsV2Async(request);
foreach (S3Object entry in response.S3Objects)
{
// Skip the folder itself and non-font files (simple check)
if (entry.Key.EndsWith("/") || !(entry.Key.EndsWith(".ttf", StringComparison.OrdinalIgnoreCase) || entry.Key.EndsWith(".otf", StringComparison.OrdinalIgnoreCase)))
{
continue;
}
context?.Logger.LogLine($"Found font file: {entry.Key}");
try
{
// Requires s3:GetObject permission on the font files
GetObjectRequest fontRequest = new GetObjectRequest
{
BucketName = bucketName,
Key = entry.Key
};
using (GetObjectResponse fontResponse = await client.GetObjectAsync(fontRequest))
{
using (MemoryStream ms = new MemoryStream())
{
await fontResponse.ResponseStream.CopyToAsync(ms);
// IMPORTANT: Aspose.PDF needs the raw byte array for MemoryFontSource.
// It manages the stream internally after this.
fontSources.Add(new MemoryFontSource(ms.ToArray()));
context?.Logger.LogLine($" -- Added MemoryFontSource for {entry.Key}");
}
}
}
catch (Exception ex)
{
context?.Logger.LogLine($" -- Failed to load font {entry.Key}: {ex.Message}");
// Decide how to handle failures - continue or stop?
}
}
request.ContinuationToken = response.NextContinuationToken;
} while (response.IsTruncated);
return fontSources;
}
/// <summary>
/// Helper method to upload a stream to an S3 bucket.
/// </summary>
private async Task<bool> PutS3Object(string bucket, string key, Stream content, ILambdaContext context)
{
try
{
PutObjectRequest request = new PutObjectRequest
{
BucketName = bucket,
Key = key,
InputStream = content,
// Set appropriate content type
ContentType = "application/pdf"
};
var response = await S3Client.PutObjectAsync(request);
context.Logger.LogLine($"S3 PutObject Response: {response.HttpStatusCode}");
return response.HttpStatusCode == System.Net.HttpStatusCode.OK;
}
catch (AmazonS3Exception s3ex)
{
context.Logger.LogLine($"Error uploading to S3: {s3ex.Message} (AWS Request ID: {s3ex.RequestId}, Error Code: {s3ex.ErrorCode})");
return false;
}
catch (Exception ex)
{
context.Logger.LogLine($"General error during S3 upload: {ex.Message}");
return false;
}
}
}
}