Write a password validation service, meant to be configurable via IoC (using dependency injection engine of your choice). The service is meant to check a text string for compliance to any number of password validation rules. The rules currently known are:

• Must consist of a mixture of lowercase letters and numerical digits only, with at least one of each.

• Must be between 5 and 12 characters in length.

• Must not contain any sequence of characters immediately followed by the same sequence.

The implementation consists of mvn project with two modules:

1. password-validation is a standalone library that can be imported in other projects.
2. password-service is a simple REST API service that uses password-validation to validate passwords.

Run the following commands:

$> mvn clean install
$> cd password-service
$> mvn spring-boot:run

The service will start listenning at http://localhost:8080. Now you can test passwords making POST requests to http://localhost:8080/api/password/validation:

{
	"password": "123abc123def"	
}

The password-validation library has a very simple yet extensible design. It has two main consists: a ValidationRule interface and a PasswordValidation class. The PasswordValiation class accepts a list of ValidationRule and validates a password against those rules.

The password-service creates a Password-Validation Spring Bean with the following rules:

@Bean
public PasswordValidation passwordValidator() {
    return new PasswordValidation(
            // length must be between 5 and 12
            new LengthRule(5, 12),

            // must consist of at least one lowercase letter
            new LowercaseRule(1),

            // must consist of at least one numerical digit
            new NumericalDigitsRule(1),

            // must consist ONLY of lowercase letters and digits
            new AllowedLetters(LowercaseRule.LETTERS + NumericalDigitsRule.DIGITS),

            // must not contain any sequence of characters immediately followed by the same sequence
            new SequenceRule()
    );
}