How to Resolve FileNotFoundException When Recursively Listing Files in Groovy

Описание: Learn how to troubleshoot the `FileNotFoundException` error caused by Groovy's `eachFileRecurse` method and ensure your file paths are correct.
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This video is based on the question https://stackoverflow.com/q/65025970/ asked by the user 'Stéphane GRILLON' ( https://stackoverflow.com/u/3535537/ ) and on the answer https://stackoverflow.com/a/65027416/ provided by the user 'cfrick' ( https://stackoverflow.com/u/3181392/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Resolve FileNotFoundException When Recursively Listing Files in Groovy

Working with file systems programmatically can often lead to complications, especially when file paths are not correctly specified or when the existence of files cannot be confidently guaranteed. If you're using Groovy for file operations and have encountered the dreaded java.io.FileNotFoundException while trying to use the eachFileRecurse method, you’re not alone. In this post, we'll dive deep into this issue and explore how to effectively resolve it.

Understanding the Problem

You might find yourself in a scenario where your Groovy script runs in a Jenkins job, attempting to list all files recursively in a specified directory. However, instead of receiving a list of files, you're greeted with the following error:

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This implies that your code is pointing to a File location that either doesn't exist or could not be accessed. The relevant Groovy snippet looks like this:

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In this code, new File("abcd/TestFlux") creates a file object but does not confirm its existence. Let’s break down how to resolve the FileNotFoundException issue.

Why the Error Occurs

File Checking Basics

It's important to understand that calling new File() does not guarantee that the specified file or directory exists. It merely creates a reference to a potential file system object. For example:

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Creating this object does not automatically check whether it exists in the file system. You might see outputs like:

exists(): Returns false if the file or directory is missing.

isDirectory(): Returns false if the specified path is not a directory.

Common Causes of the Error

Incorrect File Path: The specified path may not point to a valid directory.

Permissions Issues: The script may not have access to the specified directory.

Directory Doesn't Exist: The target directory might not exist in the expected location.

Troubleshooting Steps

Step 1: Verify the File Path

Make sure that the path you're providing to the File object is correct. Pay attention to the path prefix (absolute vs relative paths) and make sure that it accurately reflects your file system's structure.

Print the Absolute Path: Use println f.getAbsolutePath() to debug and confirm where Groovy is looking.

Step 2: Check for Existence and Types

Before attempting to iterate over the files, check if the path points to a valid directory:

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Step 3: Check Permissions

If you're running your script on a platform like Jenkins, ensure that the user executing the script has the necessary permissions to read the directory.

Example Correction

Here’s an improved version of the code that includes checks for file existence and directory validation:

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Conclusion

Encountering a java.io.FileNotFoundException when using eachFileRecurse in Groovy can be frustrating, but with a systematic approach, you can effectively troubleshoot and resolve the issue. Always ensure you're working with the correct file paths, verify file existence, and handle permissions appropriately. By following the steps outlined in this blog, you can make your file handling in Groovy more robust and reliable.

Remember, a clear understanding of how the file system interacts with your scripts is key to avoiding these types of errors in the future.