OpenIsle/backend/src/main/java/com/openisle/service/UsernameValidator.java

package com.openisle.service;

import com.openisle.exception.FieldException;
import org.apache.commons.lang3.math.NumberUtils;
import org.springframework.stereotype.Service;

/**
 * Simple validator for usernames.
 */
@Service
public class UsernameValidator {
    /**
     * Validate the username string.
     *
     * @param username the username to validate
     */
    public void validate(String username) {
        if (username == null || username.isEmpty()) {
            throw new FieldException("username", "Username cannot be empty");
        }

        if (NumberUtils.isDigits(username)) {
            throw new FieldException("username", "Username cannot be pure number");
        }
    }

}