服务器端数字指纹的最佳实践

1. 随机生成数字指纹

在服务器端生成随机的数字指纹，可以使用如下代码：

import java.math.BigInteger;
import java.security.SecureRandom;

public class DigitalFingerprintGenerator {
    private SecureRandom random = new SecureRandom();

    public String generateFingerprint() {
        return new BigInteger(130, random).toString(32);
    }
}

2. 存储数字指纹

将数字指纹与对应的用户标识存储在数据库中，可以使用如下代码：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class DigitalFingerprintStorage {
    private static final String DB_URL = "jdbc:mysql://localhost:3306/mydb";
    private static final String DB_USER = "user";
    private static final String DB_PASSWORD = "password";

    public void storeFingerprint(String fingerprint, String userId) throws SQLException {
        try(Connection conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
            PreparedStatement ps = conn.prepareStatement("INSERT INTO fingerprints (fingerprint, user_id) VALUES (?, ?)")) {
            ps.setString(1, fingerprint);
            ps.setString(2, userId);
            ps.executeUpdate();
        }
    }
}

3. 校验数字指纹

在用户访问服务器时，校验数字指纹是否正确，可以使用如下代码：

import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import java.sql.*;

public class DigitalFingerprintVerifier {
    public boolean verifyFingerprint(HttpServletRequest request) throws SQLException {
        Cookie[] cookies = request.getCookies();
        if(cookies == null) {
            return false;
        }
        
        String userId = null;
        String fingerprint = null;
        for(Cookie cookie : cookies) {
            if(cookie.getName().equals("userId")) {
                userId = cookie.getValue();
            } else if(cookie.getName().equals("fingerprint")) {
                fingerprint = cookie.getValue();
            }
        }
        
        if(userId == null || fingerprint == null) {
            return false;
        }
        
        try(Connection conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
            PreparedStatement ps = conn.prepareStatement("SELECT fingerprint FROM