Fixing java.lang.IllegalArgumentException: Illegal Base64 Character 2d

Encountering a java.lang.IllegalArgumentException: Illegal Base64 Character 2d error can be confusing for Java developers. In this post, we’ll explore the causes of this error and provide practical solutions to fix it.

Understanding

This error occurs when attempting to decode a Base64 encoded string that contains an illegal character. In this case, the character is 2d, which is the ASCII representation of the hyphen (-) character. Base64 encoded strings should only contain characters from the Base64 alphabet (A-Z, a-z, 0-9, +, and /).

Causes of java.lang.IllegalArgumentException: Illegal Base64 Character 2d

The primary cause of this error is an improperly formatted Base64 encoded string. This can occur if:

• The string was incorrectly encoded.
• The string was modified or corrupted after encoding.

Let’s look at an example that triggers a java.lang.IllegalArgumentException: Illegal Base64 Character 2d error.

import java.util.Base64;

public class Example {
 public static void main(String[] args) {
 String encodedString = "TGV0J3Mg-ExwbG9yZSBCYXNlNjQh";
 byte[] decodedBytes = Base64.getDecoder().decode(encodedString);
 String decodedString = new String(decodedBytes);
 System.out.println(decodedString);
 }
}

In this example, the encoded string contains a hyphen (-), which is not a valid Base64 character. This causes the java.lang.IllegalArgumentException: Illegal Base64 Character 2d error during decoding.

How to Fix

To fix this error, follow these steps:

1. Verify that the Base64 encoded string is properly formatted and contains only valid characters.
2. If necessary, re-encode the original data to ensure a valid Base64 encoded string.

For the example above, we could fix the error by removing the hyphen from the encoded string:

import java.util.Base64;

public class Example {
 public static void main(String[] args) {
 String encodedString = "TGV0J3MgExwbG9yZSBCYXNlNjQh";
 byte[] decodedBytes = Base64.getDecoder().decode(encodedString);
 String decodedString = new String(decodedBytes);
 System.out.println(decodedString);
 }
}

By correcting the encoded string, we can prevent the java.lang.IllegalArgumentException: Illegal Base64 Character 2d error from occurring.

Best Practices to Prevent java.lang.IllegalArgumentException: Illegal Base64 Character 2d

Follow these best practices to avoid encountering the java.lang.IllegalArgumentException: Illegal Base64 Character 2d error in your Java projects:

• Ensure that you are using a reliable Base64 encoding and decoding library, such as the built-in java.util.Base64 class or a well-maintained third-party library.
• Validate the Base64 encoded strings before attempting to decode them, checking for invalid characters or incorrect padding.
• Store Base64 encoded strings securely and avoid modifying them manually to prevent accidental corruption.

Conclusion

In this post, we’ve learned about the java.lang.IllegalArgumentException: Illegal Base64 Character 2d error, its causes, and how to fix it. By following best practices and understanding the error’s origin, you can prevent it from occurring in your Java projects and ensure smooth data encoding and decoding.

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