Resolving IllegalArgumentException: Illegal Base64 Character 20

The IllegalArgumentException: Illegal Base64 Character 20 is a common error that Java developers may encounter when working with Base64 encoded strings. This error occurs when an invalid character is present in the Base64 encoded string while trying to decode it. In this post, we will discuss the causes of this error and provide practical solutions to fix it.

Understanding

The IllegalArgumentException is a runtime exception that occurs when a method receives an argument with an inappropriate value. The Illegal Base64 Character 20 error specifically occurs when the Base64 decoder encounters an illegal character, such as a space, in the encoded string. Base64 encoding uses a specific set of characters, and any deviation from this set can lead to this error.

Causes of IllegalArgumentException: Illegal Base64 Character 20

Here are some common reasons why this error might occur:

• The Base64 encoded string contains an invalid character (in this case, a space or 0x20).
• The encoded string was corrupted or altered during transmission or storage.
• Manual editing of the Base64 encoded string introduced the error.

For example, consider the following code that attempts to decode an invalid Base64 encoded string:

import java.util.Base64;

public class Example {
 public static void main(String[] args) {
 String encodedString = "TGV0J3Mg ExwbG9yZSBCYXNlNjQ";
 byte[] decodedBytes = Base64.getDecoder().decode(encodedString);
 String decodedString = new String(decodedBytes);
 System.out.println(decodedString);
 }
}

In this example, the encoded string contains a space (0x20), which is an invalid Base64 character. This causes the IllegalArgumentException: Illegal Base64 Character 20 error at runtime.

How to Fix IllegalArgumentException: Illegal Base64 Character 20

To fix this error, follow these steps:

1. Identify the invalid Base64 encoded string causing the error.
2. Remove or replace the invalid characters in the encoded string.
3. Use a reliable Base64 encoding and decoding library, such as the built-in java.util.Base64 class.

For the example above, we can fix the error by removing the space from the encoded string:

import java.util.Base64;

public class Example {
public static void main(String[] args) {
String encodedString = "TGV0J3MgExwbG9yZSBCYXNlNjQ";
byte[] decodedBytes = Base64.getDecoder().decode(encodedString);
String decodedString = new String(decodedBytes);
System.out.println(decodedString);
}
}

By removing the space from the encoded string, we can prevent the error from occurring at runtime.

Best Practices to Prevent

Follow these best practices to avoid encountering the error in your Java projects:

• Ensure that your Base64 encoded strings are properly generated and contain only valid characters.
• Validate and sanitize input strings before passing them to the Base64 decoding method.
• Use a reliable Base64 encoding and decoding library, such as the built-in java.util.Base64 class, to ensure consistent results.

Conclusion

In this post, we’ve learned about the IllegalArgumentException: Illegal Base64 Character 20, 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 runtime execution.

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