Скачать или смотреть Resolving the Font Not Found Error in Apache POI XLSX Export on Azure Web App

Discover how to fix the frustrating `Font not found` error while using Apache POI for XLSX exports in your Azure Web App. Learn why this issue occurs and how to quickly roll back your Apache Tomcat version.
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Troubleshooting Font Errors in Apache POI XLSX Exports on Azure Web Apps

If you're experiencing a sudden Font not found error while generating XLSX files with Apache POI in your Azure web application, you're not alone. This problem has been reported by various developers and can be particularly frustrating, especially when it seems to arise out of nowhere. The error typically occurs when the application is unable to locate the necessary font resources required for rendering documents, often due to changes in the underlying environment.

Understanding the Issue

In a recent occurrence, a developer found their Java application — which had been using Apache POI to generate XLSX exports — throwing a font-related error unexpectedly. The application had been functioning perfectly for months without any changes to the font configuration on the Azure web service. However, the error was triggered when the worksheet creation method attempted to reference a font that was no longer available in the environment.

Here’s a significant portion of the error stack trace:

[[See Video to Reveal this Text or Code Snippet]]

Diagnosing the Problem

Upon closer inspection, it was identified that the application deployed on Azure App Service was operating on a specific version of Apache Tomcat. An automatic update within the Azure configuration that happened to coincide with the error introduction had switched the Java provider to OpenJDK. This change led to the absence of necessary fonts that were previously available with the older Tomcat configuration.

Steps to Resolve the Font Not Found Error

Step 1: Roll Back the Apache Tomcat Version

To resolve the issue, the simple solution is to rollback to a previous version of Apache Tomcat that includes the correct font configurations. Here’s how you can do that:

Log into the Azure Portal: Go to your Azure App Service configuration settings.

Navigate to Configuration: Click on the ‘Configuration’ tab in your App Service settings.

Locate Tomcat Version Settings: Check the configured Tomcat version and look for an option to change or rollback the version.

Select an Earlier Version (e.g., 8.5.66): Changing the version to 8.5.66 or another suitable version that includes the font support should resolve the font errors.

Step 2: Verify the Changes

After rolling back to the older version, it’s important to test your application to ensure that the XLSX export feature is functioning correctly again. If the functionality returns, it indicates that the problem was indeed related to the change in Java providers and the absence of font resources.

Conclusion

The Font not found error when generating XLSX exports with Apache POI can be a challenging issue, especially when it arises unexpectedly due to changes in your environment. By understanding the root cause and reverting to an earlier version of Apache Tomcat, you can mitigate this error effectively.

If you encounter similar issues in the future, remember to check for any recent automatic updates that might affect your app's performance, especially regarding external libraries and configurations. Happy coding!