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/* * 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; import java.io.Serializable; /** * Abstract <b>Modulus</b> Check digit calculation/validation. * <p> * Provides a <i>base</i> class for building <i>modulus</i> Check Digit routines. * <p> * This implementation only handles <i>numeric</i> codes, such as <b>EAN-13</b>. For <i>alphanumeric</i> codes such as * <b>EAN-128</b> you will need to implement/override the <code>toInt()</code> and <code>toChar()</code> methods. * <p> * * @version $Revision: 909004 $ $Date: 2010-02-11 14:44:57 +0000 (Qui, 11 Fev 2010) $ * @since Validator 1.4 */ public abstract class ModulusCheckDigit implements CheckDigit, Serializable { private final int modulus; /** * Construct a {@link CheckDigit} routine for a specified modulus. * * @param modulus The modulus value to use for the check digit calculation */ public ModulusCheckDigit(int modulus) { this.modulus = modulus; } /** * Return the modulus value this check digit routine is based on. * * @return The modulus value this check digit routine is based on */ public int getModulus() { return modulus; } /** * Validate a modulus check digit for a code. * * @param code The code to validate * @return <code>true</code> if the check digit is valid, otherwise <code>false</code> */ @Override public boolean isValid(String code) { if (code == null || code.length() == 0) { return false; } try { int modulusResult = calculateModulus(code, true); return (modulusResult == 0); } catch (CheckDigitException ex) { return false; } } /** * Calculate a modulus <i>Check Digit</i> for a code. * * @param code The code to calculate the Check Digit for * @return The calculated Check Digit * @throws CheckDigitException if an error occurs calculating * the check digit for the specified code */ @Override public String calculate(String code) throws CheckDigitException { if (code == null || code.length() == 0) { throw new CheckDigitException("Code is missing"); } int modulusResult = calculateModulus(code, false); int charValue = (modulus - modulusResult) % modulus; return toCheckDigit(charValue); } /** * Calculate the modulus for a 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 { int total = 0; for (int i = 0; i < code.length(); i++) { int lth = code.length() + (includesCheckDigit ? 0 : 1); int leftPos = i + 1; int rightPos = lth - i; int charValue = toInt(code.charAt(i), leftPos, rightPos); total += weightedValue(charValue, leftPos, rightPos); } if (total == 0) { throw new CheckDigitException("Invalid code, sum is zero"); } return (total % modulus); } /** * Calculates the <i>weighted</i> value of a character in the * code at a specified position. * <p> * Some modulus routines weight the value of a character depending on its position in the code (e.g. ISBN-10), while others * use different weighting factors for odd/even positions (e.g. EAN or Luhn). Implement the appropriate mechanism required by * overriding this method. * * @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 * @throws CheckDigitException if an error occurs calculating * the weighted value */ protected abstract int weightedValue(int charValue, int leftPos, int rightPos) throws CheckDigitException; /** * Convert a character at a specified position to an integer value. * <p> * <b>Note:</b> this implementation only handlers numeric values For non-numeric characters, override this method to provide * character-->integer conversion. * * @param character The character to convert * @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 integer value of the character * @throws CheckDigitException if character is non-numeric */ protected int toInt(char character, int leftPos, int rightPos) throws CheckDigitException { if (Character.isDigit(character)) { return Character.getNumericValue(character); } else { throw new CheckDigitException("Invalid Character[" + leftPos + "] = '" + character + "'"); } } /** * Convert an integer value to a check digit. * <p> * <b>Note:</b> this implementation only handles numeric values For non-numeric characters, override this method to provide * integer-->character conversion. * * @param charValue The integer value of the character * @return The converted character * @throws CheckDigitException if integer character value * doesn't represent a numeric character */ protected String toCheckDigit(int charValue) throws CheckDigitException { if (charValue >= 0 && charValue <= 9) { return Integer.toString(charValue); } else { throw new CheckDigitException("Invalid Check Digit Value =" + +charValue); } } /** * Add together the individual digits in a number. * * @param number The number whose digits are to be added * @return The sum of the digits */ public static int sumDigits(int number) { int total = 0; int todo = number; while (todo > 0) { total += todo % 10; todo = todo / 10; } return total; } }