👀 Views: 59 💬 Answers: 1 📅 Created: 2025-06-09

regex base64 validation Java

I'm reviewing some code and I'm upgrading from an older version and I'm converting an old project and Quick question that's been bugging me - After trying multiple solutions online, I still can't figure this out... I'm working on validating Base64 encoded strings in a Java application, specifically using Java 11's `Pattern` and `Matcher` classes. My regex pattern is supposed to match strings that are valid Base64, including proper padding with `=` characters. However, I'm working with issues when the input string is at the edge of valid Base64 encoding, particularly when the strings have one or two padding characters. Here's the regex I've been using: ```java String regex = "^[A-Za-z0-9+/]*={0,2}$"; Pattern pattern = Pattern.compile(regex); Matcher matcher = pattern.matcher(inputString); if (!matcher.matches()) { System.out.println("Invalid Base64 string"); } else { System.out.println("Valid Base64 string"); } ``` When I test with strings like `SGVsbG8=`, it works fine. However, strings like `SGVsbG8=` and `SGVsbG8` (without padding) are not being captured correctly, leading to unexpected behavior. The output is `Invalid Base64 string` for `SGVsbG8`, even though it should be valid. I understand that Base64 encoded strings can be of various lengths and may not always include padding; however, my regex seems to reject valid strings that do not use padding when they are a multiple of 3 characters. I've also tried tweaking the regex pattern with other variations like `^[A-Za-z0-9+/]*={0,2}$` but this doesn't seem to resolve the scenario either. Could someone please guide to refine this regex to accurately handle these edge cases? Any insights into how to properly accommodate both padded and non-padded Base64 strings would be greatly appreciated. Has anyone else encountered this? I'm working on a API that needs to handle this. I'd really appreciate any guidance on this. I'm working on a web app that needs to handle this. Any ideas how to fix this? The stack includes Java and several other technologies. Is this even possible? I'm working in a Linux environment. Any examples would be super helpful. For context: I'm using Java on Windows 11.