ModulusCheckDigit.java
/*
* 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;
import org.apache.commons.validator.GenericValidator;
/**
* Abstract <b>Modulus</b> Check digit calculation/validation.
* <p>
* Provides a <i>base</i> class for building <i>modulus</i> Check Digit routines.
* </p>
* <p>
* This implementation only handles <i>single-digit 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>
*
* @since 1.4
*/
public abstract class ModulusCheckDigit extends AbstractCheckDigit implements Serializable {
static final int MODULUS_10 = 10;
static final int MODULUS_11 = 11;
private static final long serialVersionUID = 2948962251251528941L;
/**
* 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(final int number) {
int total = 0;
int todo = number;
while (todo > 0) {
total += todo % 10; // CHECKSTYLE IGNORE MagicNumber
todo /= 10; // CHECKSTYLE IGNORE MagicNumber
}
return total;
}
/**
* The modulus can be greater than 10 provided that the implementing class overrides toCheckDigit and toInt (for example as in ISBN10CheckDigit).
*/
private final int modulus;
/**
* Constructs a modulus 10 {@link CheckDigit} routine for a specified modulus.
*/
ModulusCheckDigit() {
this(MODULUS_10);
}
/**
* Constructs a {@link CheckDigit} routine for a specified modulus.
*
* @param modulus The modulus value to use for the check digit calculation
*/
public ModulusCheckDigit(final int modulus) {
this.modulus = modulus;
}
/**
* Calculate a modulus <i>Check Digit</i> for a code which does not yet have one.
*
* @param code The code for which to calculate the Check Digit;
* the check digit should not be included
* @return The calculated Check Digit
* @throws CheckDigitException if an error occurs calculating the check digit
*/
@Override
public String calculate(final String code) throws CheckDigitException {
if (GenericValidator.isBlankOrNull(code)) {
throw new CheckDigitException("Code is missing");
}
final int modulusResult = calculateModulus(code, false);
final 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(final String code, final boolean includesCheckDigit) throws CheckDigitException {
int total = 0;
for (int i = 0; i < code.length(); i++) {
final int lth = code.length() + (includesCheckDigit ? 0 : 1);
final int leftPos = i + 1;
final int rightPos = lth - i;
final 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;
}
/**
* Gets 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} if the check digit is valid, otherwise
* {@code false}
*/
@Override
public boolean isValid(final String code) {
if (GenericValidator.isBlankOrNull(code)) {
return false;
}
try {
final int modulusResult = calculateModulus(code, true);
return modulusResult == 0;
} catch (final CheckDigitException ex) {
return false;
}
}
/**
* Convert an integer value to a check digit.
* <p>
* <b>Note:</b> this implementation only handles single-digit 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(final int charValue) throws CheckDigitException {
if (charValue >= 0 && charValue <= 9) { // CHECKSTYLE IGNORE MagicNumber
return Integer.toString(charValue);
}
throw new CheckDigitException("Invalid Check Digit Value =" + +charValue);
}
/**
* 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 (for identifiying the position in the string)
* @param rightPos The position of the character in the code, counting from right to left (not used here)
* @return The integer value of the character
* @throws CheckDigitException if character is non-numeric
*/
protected int toInt(final char character, final int leftPos, final int rightPos) throws CheckDigitException {
if (Character.isDigit(character)) {
return Character.getNumericValue(character);
}
throw new CheckDigitException("Invalid Character[" + leftPos + "] = '" + character + "'");
}
/**
* 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;
}