前言
在开发应用程序时，为了保障系统的安全性，我们常常需要对用户的登录行为进行限制，比如规定用户在 5 分钟内最多允许尝试登录 3 次，如果超过次数，就锁定当前用户。今天我们就来探讨几种在 Java 中实现这一功能的方案，让我们的系统更加安全可靠。
使用 HashMap 和 Timer 实现
首先，我们创建一个 HashMap 来存储用户登录失败的信息。这个 HashMap 中的键是用户名，而值是一个自定义的 LoginAttempt 对象，它包含登录失败次数和最近一次失败时间。当用户进行登录操作时，我们会检查 HashMap 中是否存在该用户的记录。若存在，会查看是否超过 5 分钟，如果超过，我们将重置失败次数；如果未超过且次数已达 3 次，将拒绝登录。同时，我们使用 Timer 来清理过期的记录。
示例
public class LoginAttempt {
int attempts;
long lastAttemptTime;
public LoginAttempt() {
this.attempts = 0;
this.lastAttemptTime = System.currentTimeMillis();
}
}
public class LoginService {
private static final Map<String, LoginAttempt> loginAttempts = new HashMap<>();
private static final long LOCKOUT_DURATION = 5 * 60 * 1000; // 5 minutes in milliseconds
private static final int MAX_ATTEMPTS = 3;
public static boolean isLoginAllowed(String username) {
LoginAttempt attempt = loginAttempts.get(username);
if (attempt == null) {
return true;
}
long currentTime = System.currentTimeMillis();
if (currentTime - attempt.lastAttemptTime > LOCKOUT_DURATION) {
loginAttempts.remove(username);
return true;
}
if (attempt.attempts >= MAX_ATTEMPTS) {
return false;
}
return true;
}
public static void recordFailedLogin(String username) {
LoginAttempt attempt = loginAttempts.get(username);
if (attempt == null) {
attempt = new LoginAttempt();
loginAttempts.put(username, attempt);
}
attempt.attempts++;
attempt.lastAttemptTime = System.currentTimeMillis();
}
public static void main(String[] args) {
Timer timer = new Timer();
timer.scheduleAtFixedRate(new TimerTask() {
@Override
public void run() {
long currentTime = System.currentTimeMillis();
loginAttempts.entrySet().removeIf(entry -> currentTime - entry.getValue().lastAttemptTime > LOCKOUT_DURATION);
}
}, LOCKOUT_DURATION, LOCKOUT_DURATION);
// 模拟登录尝试
String username = "testUser";
for (int i = 0; i < 5; i++) {
if (isLoginAllowed(username)) {
System.out.println("Login allowed");
// 模拟登录成功，重置尝试次数
loginAttempts.remove(username);
} else {
System.out.println("Login not allowed, user locked");
}
recordFailedLogin(username);
}
}
}使用 ConcurrentHashMap 和 ScheduledExecutorService 实现
这里我们使用 ConcurrentHashMap 来存储用户登录失败信息，它支持并发访问。并且使用 ScheduledExecutorService 来进行定时清理过期记录，避免 Timer 的一些潜在问题，如可能导致的内存泄漏，更适合高并发场景。
示例
public class LoginAttempt {
int attempts;
long lastAttemptTime;
public LoginAttempt() {
this.attempts = 0;
this.lastAttemptTime = System.currentTimeMillis();
}
}
public class LoginService {
private static final ConcurrentHashMap<String, LoginAttempt> loginAttempts = new ConcurrentHashMap<>();
private static final long LOCKOUT_DURATION = 5 * 60 * 1000; // 5 minutes in milliseconds
private static final int MAX_ATTEMPTS = 3;
private static final ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
static {
executorService.scheduleAtFixedRate(() -> {
long currentTime = System.currentTimeMillis();
loginAttempts.entrySet().removeIf(entry -> currentTime - entry.getValue().lastAttemptTime > LOCKOUT_DURATION);
}, LOCKOUT_DURATION, LOCKOUT_DURATION, TimeUnit.MILLISECONDS);
}
public static boolean isLoginAllowed(String username) {
LoginAttempt attempt = loginAttempts.get(username);
if (attempt == null) {
return true;
}
long currentTime = System.currentTimeMillis();
if (currentTime - attempt.lastAttemptTime > LOCKOUT_DURATION) {
loginAttempts.remove(username);
return true;
}
if (attempt.attempts >= MAX_ATTEMPTS) {
return false;
}
return true;
}
public static void recordFailedLogin(String username) {
loginAttempts.compute(username, (key, value) -> {
if (value == null) {
return new LoginAttempt();
}
value.attempts++;
value.lastAttemptTime = System.currentTimeMillis();
return value;
});
}
public static void main(String[] args) {
// 模拟登录尝试
String username = "testUser";
for (int i = 0; i < 5; i++) {
if (isLoginAllowed(username)) {
System.out.println("Login allowed");
// 模拟登录成功，重置尝试次数
loginAttempts.remove(username);
} else {
System.out.println("Login not allowed, user locked");
}
recordFailedLogin(username);
}
}
}使用 Redis 存储登录尝试信息
借助 Redis 的键值存储，我们将用户的登录失败次数和最近一次失败时间存储起来，并利用 Redis 的 TTL（Time To Live）功能自动清理过期记录。在用户登录时，从 Redis 获取信息，据此判断是否允许登录。
示例
public class LoginService {
private static final Jedis jedis = new Jedis("localhost", 6379);
private static final long LOCKOUT_DURATION = 5 * 60; // 5 minutes in seconds
private static final int MAX_ATTEMPTS = 3;
public static boolean isLoginAllowed(String username) {
String attemptsKey = "login_attempts:" + username;
String attemptsStr = jedis.get(attemptsKey);
if (attemptsStr == null) {
return true;
}
String[] parts = attemptsStr.split(":");
int attempts = Integer.parseInt(parts[0]);
long lastAttemptTime = Long.parseLong(parts[1]);
long currentTime = System.currentTimeMillis() / 1000;
if (currentTime - lastAttemptTime > LOCKOUT_DURATION) {
jedis.del(attemptsKey);
return true;
}
if (attempts >= MAX_ATTEMPTS) {
return false;
}
return true;
}
public static void recordFailedLogin(String username) {
String attemptsKey = "login_attempts:" + username;
String attemptsStr = jedis.get(attemptsKey);
long currentTime = System.currentTimeMillis() / 1000;
if (attemptsStr == null) {
jedis.setex(attemptsKey, (int) LOCKOUT_DURATION, "1:" + currentTime);
} else {
String[] parts = attemptsStr.split(":");
int attempts = Integer.parseInt(parts[0]);
jedis.setex(attemptsKey, (int) LOCKOUT_DURATION, (attempts + 1) + ":" + currentTime);
}
}
public static void main(String[] args) {
// 模拟登录尝试
String username = "testUser";
for (int i = 0; i < 5; i++) {
if (isLoginAllowed(username)) {
System.out.println("Login allowed");
// 模拟登录成功，删除尝试记录
jedis.del("login_attempts:" + username);
} else {
System.out.println("Login not allowed, user locked");
}
recordFailedLogin(username);
}
}
}补充-滑动窗口
构造一个滑动窗口，窗口大小限制5分钟，然后限流次数设置为3次即可实现这个功能了。而滑动窗口我们可以借助Redis来实现。
public class SlidingWindowRateLimiter {
private Jedis jedis;
private String key;
private int limit = 3; //限制请求次数最大3次
private int lockTime; // 锁定用户的时间，单位：秒
public SlidingWindowRateLimiter(Jedis jedis, String key, int limit, int lockTime) {
this.jedis = jedis;
this.key = key;
this.limit = limit;
this.lockTime = lockTime; // 锁定时间
}
public boolean allowRequest() {
// 当前时间戳，单位：毫秒
long currentTime = System.currentTimeMillis();
// 锁定键的名称（锁定的用户）
String lockKey = "lock:" + key;
// 检查用户是否已被锁定
if (jedis.exists(lockKey)) {
returnfalse; // 用户已被锁定，返回 false
}
// 使用Lua脚本来确保原子性操作
String luaScript = "local window_start = ARGV[1] - 300000\n" + // 计算5分钟的起始时间
"redis.call('ZREMRANGEBYSCORE', KEYS[1], '-inf', window_start)\n" + // 清理过期的请求
"local current_requests = redis.call('ZCARD', KEYS[1])\n" + // 获取当前请求次数
"if current_requests < tonumber(ARGV[2]) then\n" + // 如果请求次数小于限制
" redis.call('ZADD', KEYS[1], ARGV[1], ARGV[1])\n" + // 添加当前请求时间
" return 1\n" + // 允许请求
"else\n" +
" redis.call('SET', 'lock:'..KEYS[1], 1, 'EX', tonumber(ARGV[3]))\n" + // 锁定用户
" return 0\n" + // 拒绝请求
"end";
// 调用 Lua 脚本进行原子操作
Object result = jedis.eval(luaScript, 1, key, String.valueOf(currentTime), String.valueOf(limit), String.valueOf(lockTime));
// 返回操作结果
return (Long) result == 1;
}
}使用 Spring Security 实现
我们还可以使用 Spring Security 的相关组件来实现。利用 AuthenticationFailureHandler 记录登录失败信息，在 UserDetailsService 的 loadUserByUsername 方法中检查用户是否被锁定，使用 UserDetails 的 isAccountNonLocked 属性表示用户是否被锁定。
示例
public class CustomAuthenticationProvider implements AuthenticationProvider {
private UserDetailsService userDetailsService;
private PasswordEncoder passwordEncoder;
private Map<String, LoginAttempt> loginAttempts = new HashMap<>();
private static final long LOCKOUT_DURATION = 5 * 60 * 1000; // 5 minutes in milliseconds
private static final int MAX_ATTEMPTS = 3;
public CustomAuthenticationProvider(UserDetailsService userDetailsService) {
this.userDetailsService = userDetailsService;
this.passwordEncoder = new BCryptPasswordEncoder();
}
@Override
public Authentication authenticate(Authentication authentication) throws AuthenticationException {
String username = authentication.getName();
String password = authentication.getCredentials().toString();
UserDetails userDetails;
try {
userDetails = userDetailsService.loadUserByUsername(username);
} catch (UsernameNotFoundException e) {
throw new BadCredentialsException("Invalid username or password");
}
if (!passwordEncoder.matches(password, userDetails.getPassword())) {
recordFailedLogin(username);
throw new BadCredentialsException("Invalid username or password");
}
if (!isLoginAllowed(username)) {
throw new BadCredentialsException("User is locked");
}
return new UsernamePasswordAuthenticationToken(userDetails, password, userDetails.getAuthorities());
}
private boolean isLoginAllowed(String username) {
LoginAttempt attempt = loginAttempts.get(username);
if (attempt == null) {
return true;
}
long currentTime = System.currentTimeMillis();
if (currentTime - attempt.lastAttemptTime > LOCKOUT_DURATION) {
loginAttempts.remove(username);
return true;
}
if (attempt.attempts >= MAX_ATTEMPTS) {
return false;
}
return true;
}
private void recordFailedLogin(String username) {
LoginAttempt attempt = loginAttempts.get(username);
if (attempt == null) {
attempt = new LoginAttempt();
loginAttempts.put(username, attempt);
}
attempt.attempts++;
attempt.lastAttemptTime = System.currentTimeMillis();
}
@Override
public boolean supports(Class<?> authentication) {
return authentication.equals(UsernamePasswordAuthenticationToken.class);
}
public static class LoginAttempt {
int attempts;
long lastAttemptTime;
public LoginAttempt() {
this.attempts = 0;
this.lastAttemptTime = System.currentTimeMillis();
}
}
}最后
如果你是单机应用，ConcurrentHashMap 和 ScheduledExecutorService 可能是个不错的选择；如果是分布式系统，使用 Redis 方案会更有优势；而对于 Spring 框架的项目，Spring Security 方案会更贴合你的需求。
