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Thread: Base64 encoding is not working.

  1. #1
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    Default Base64 encoding is not working.

    Hello,

    I searched a lot to find a proper base64 encoding and decoding mechanism. I found the below link useful to me:

    Convert Between Base 10, Base 62, Base 36, Base 16, Base 8, Base 2 in Java

    The thing is that my database tables have keys which are in the below format:
    key = uniqueObjectClassName+ Base64 encoded string.
    A sample encoded string from DB is: "0003}C".

    I used the decoding code from the above link:

        public static int fromBase64( String base64Number ) {
            return fromOtherBaseToDecimal( 64, base64Number );
        }
     
        private static int fromOtherBaseToDecimal( int base, String number ) {
            int iterator = number.length();
            int returnValue = 0;
            int multiplier = 1;
     
            while( iterator > 0 ) {
                returnValue = returnValue + ( baseDigits.indexOf( number.substring( iterator - 1, iterator ) ) * multiplier );
                multiplier = multiplier * base;
                --iterator;
            }
            return returnValue;
        }
     
        public static void main(String[] args) {
     
    		System.out.println(BaseConverterUtil.fromBase64("0003}C"));
    }

    And the result is: 12236. I checked this in the vendors GUI and confirmed that it is correct. However when I use this String - "12236" and call the encoding API:

        public static String toBase64( int decimalNumber ) {
            return fromDecimalToOtherBase( 64, decimalNumber );
        }
     
        private static String fromDecimalToOtherBase ( int base, int decimalNumber ) {
            String tempVal = decimalNumber == 0 ? "0" : "";
            int mod = 0;
            while( decimalNumber != 0 ) {
                mod = decimalNumber % base;
                	tempVal = baseDigits.substring( mod, mod + 1 ) + tempVal;
                decimalNumber = decimalNumber / base;
            }
            return tempVal;
        }

    I get the below exception:

    Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 64

    It should ideally return me: "0003}C". Can any one help ?


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Base64 encoding is not working.

    Please post the full text of the error message. It has important info that you left off.

  3. #3
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    Default Re: Base64 encoding is not working.

    Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 64
    at java.lang.String.substring(String.java:1935)
    at BaseConverterUtil.fromDecimalToOtherBase(BaseConve rterUtil.java:62)
    at BaseConverterUtil.toBase64(BaseConverterUtil.java: 54)
    at BaseConverterUtil.main(BaseConverterUtil.java:85)
    So line BaseConverterUtil.java:62 [fromDecimalToOtherBase()] is:

    tempVal = baseDigits.substring( mod, mod + 1 ) + tempVal;

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Base64 encoding is not working.

    From the error message I'd say the String has less than 65 characters and the code is trying to access the 65th char (arrays are 0 based so 64 is index of 65th).

    Add some printlns to show the values being used if you can't see what is happening.

  5. #5
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    Default Re: Base64 encoding is not working.

    Well thats true, thats a plain explanation. But I expected someone to correct the encoding logic.

  6. #6
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    Default Re: Base64 encoding is not working.

    I expected someone to correct the encoding logic.
    You need to learn how to do that. We'll try to help you fix your code.

    What is the length of the String that is being called with substring?
    What was the value of base?

  7. #7
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    Default Re: Base64 encoding is not working.

    Never mind, I fixed it. Thanks.

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