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Apache Commons Validator provides the building blocks for both client side validation and server side data validation.
It may be used standalone or with a framework like Struts.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.validator.routines.checkdigit;
/**
* Modulus 10 ISIN (International Securities Identifying Number) Check Digit calculation/validation.
*
*
* ISIN Numbers are 12 character alphanumeric codes used
* to identify Securities.
*
*
*
* Check digit calculation uses the Modulus 10 Double Add Double technique
* with every second digit being weighted by 2. Alphabetic characters are
* converted to numbers by their position in the alphabet starting with A being 10.
* Weighted numbers greater than ten are treated as two separate numbers.
*
*
*
* See Wikipedia - ISIN
* for more details.
*
*
* @version $Revision: 1713331 $
* @since Validator 1.4
*/
public final class ISINCheckDigit extends ModulusCheckDigit {
private static final long serialVersionUID = -1239211208101323599L;
/** Singleton ISIN Check Digit instance */
public static final CheckDigit ISIN_CHECK_DIGIT = new ISINCheckDigit();
/** weighting given to digits depending on their right position */
private static final int[] POSITION_WEIGHT = new int[] {2, 1};
/**
* Construct an ISIN Indetifier Check Digit routine.
*/
public ISINCheckDigit() {
super(10);
}
/**
* Calculate the modulus for an ISIN code.
*
* @param code The code to calculate the modulus for.
* @param includesCheckDigit Whether the code includes the Check Digit or not.
* @return The modulus value
* @throws CheckDigitException if an error occurs calculating the modulus
* for the specified code
*/
protected int calculateModulus(String code, boolean includesCheckDigit) throws CheckDigitException {
StringBuilder transformed = new StringBuilder(code.length() * 2);
if (includesCheckDigit) {
char checkDigit = code.charAt(code.length()-1); // fetch the last character
if (!Character.isDigit(checkDigit)){
throw new CheckDigitException("Invalid checkdigit["+ checkDigit+ "] in " + code);
}
}
for (int i = 0; i < code.length(); i++) {
int charValue = Character.getNumericValue(code.charAt(i));
if (charValue < 0 || charValue > 35) {
throw new CheckDigitException("Invalid Character[" +
(i + 1) + "] = '" + charValue + "'");
}
// this converts alphanumerics to two digits
// so there is no need to overload toInt()
transformed.append(charValue);
}
return super.calculateModulus(transformed.toString(), includesCheckDigit);
}
/**
* Calculates the weighted value of a charcter in the
* code at a specified position.
*
* For Luhn (from right to left) odd digits are weighted
* with a factor of one and even digits with a factor
* of two. Weighted values > 9, have 9 subtracted
*
* @param charValue The numeric value of the character.
* @param leftPos The position of the character in the code, counting from left to right
* @param rightPos The positionof the character in the code, counting from right to left
* @return The weighted value of the character.
*/
protected int weightedValue(int charValue, int leftPos, int rightPos) {
int weight = POSITION_WEIGHT[rightPos % 2];
int weightedValue = (charValue * weight);
return ModulusCheckDigit.sumDigits(weightedValue);
}
}