Package org.apache.bval.extras.constraints.checkdigit

Class LuhnValidator

java.lang.Object

org.apache.bval.extras.constraints.checkdigit.LuhnValidator

All Implemented Interfaces:

javax.validation.ConstraintValidator<Luhn,CharSequence>

public final class LuhnValidator
extends Object

Modulus 10 Luhn Check Digit calculation/validation.

Luhn check digits are used, for example, by:

• Credit Card Numbers
• IMEI Numbers - International Mobile Equipment Identity Numbers

Check digit calculation is based on modulus 10 with digits in an odd position (from right to left) being weighted 1 and even position digits being weighted 2 (weighted values greater than 9 have 9 subtracted).

See Wikipedia for more details.

Constructor Summary

Constructors

Constructor	Description
LuhnValidator()

Method Summary

Modifier and Type	Method	Description
void	initialize(A annotation)
boolean	isValid(CharSequence code, javax.validation.ConstraintValidatorContext context)
protected static int	sumDigits(int number)	Add together the individual digits in a number.
protected int	toInt(char character, int leftPos, int rightPos)	Convert a character at a specified position to an integer value.
protected int	weightedValue(int charValue, int leftPos, int rightPos)	Calculates the weighted value of a charcter in the code at a specified position.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LuhnValidator

public LuhnValidator()

Method Detail

weightedValue

protected int weightedValue(int charValue,
                            int leftPos,
                            int rightPos)
                     throws Exception

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

Calculates the weighted value of a character in the code at a specified position.

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.

Parameters:

charValue - The numeric value of the character

leftPos - The position of the character in the code, counting from left to right

rightPos - The position of the character in the code, counting from right to left

Returns:

The weighted value of the character

Throws:

Exception

initialize

public final void initialize(A annotation)

Specified by:

initialize in interface javax.validation.ConstraintValidator<A extends Annotation,CharSequence>

isValid

public boolean isValid(CharSequence code,
                       javax.validation.ConstraintValidatorContext context)

Specified by:

isValid in interface javax.validation.ConstraintValidator<A extends Annotation,CharSequence>

toInt

protected int toInt(char character,
                    int leftPos,
                    int rightPos)

Convert a character at a specified position to an integer value.

Note: this implementation only handlers numeric values For non-numeric characters, override this method to provide character-->integer conversion.

Parameters:

character - The character to convert

leftPos - The position of the character in the code, counting from left to right

rightPos - The positionof the character in the code, counting from right to left

Returns:

The integer value of the character

sumDigits

protected static int sumDigits(int number)

Add together the individual digits in a number.

Parameters:

number - The number whose digits are to be added

Returns:

The sum of the digits