一、Lock4j 简介
Lock4j 是阿里巴巴开源的分布式锁组件，支持 Redis、Zookeeper 等多种实现，与 Spring Boot 无缝集成。
二、快速开始
1. 添加依赖
<dependency> <groupId>com.baomidou</groupId> <artifactId>lock4j-redis-template-spring-boot-starter</artifactId> <version>2.2.0</version> </dependency> <!-- 如果使用 Redis，需要同时引入 Redis 依赖 --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> </dependency>2. 配置文件
spring: redis: host: localhost port: 6379 lock4j: # 锁的默认过期时间(ms)，超时自动释放 acquire-timeout: 3000 # 获取锁的超时时间(ms)，超时则获取失败 expire: 30000 # 主线程等待锁的时间，超时则抛出异常 primary-timeout: 30003. 基础使用
@Service public class UserService { @Autowired private UserMapper userMapper; // 基本用法：锁的key为 "user:lock:" + id @Lock4j(keys = {"#id"}, expire = 10000, acquireTimeout = 3000) public void updateUser(Long id, String name) { User user = userMapper.selectById(id); user.setName(name); userMapper.updateById(user); } }三、核心注解详解
@Lock4j 注解参数
| 参数 | 说明 | 默认值 |
|---|---|---|
| keys | 锁的key，支持SpEL表达式 | 空 |
| expire | 锁的过期时间(ms) | 配置中的值 |
| acquireTimeout | 获取锁超时时间(ms) | 配置中的值 |
| name | 锁的名称前缀 | 空 |
四、实战示例
1. 防重复提交
@RestController public class OrderController { @PostMapping("/order/create") @Lock4j(keys = {"#userId"}, expire = 5000, acquireTimeout = 1000) public Result createOrder(@RequestBody OrderVO orderVO, @RequestParam Long userId) { // 业务逻辑 return Result.success(); } }2. 库存扣减（MyBatis-Plus 操作）
@Service public class ProductService { @Autowired private ProductMapper productMapper; @Lock4j(keys = {"#productId"}, expire = 5000, acquireTimeout = 3000) @Transactional(rollbackFor = Exception.class) public boolean deductStock(Long productId, Integer quantity) { // 1. 查询商品 Product product = productMapper.selectById(productId); // 2. 检查库存 if (product.getStock() < quantity) { throw new RuntimeException("库存不足"); } // 3. 扣减库存 product.setStock(product.getStock() - quantity); int result = productMapper.updateById(product); return result > 0; } }3. 复杂SpEL表达式
@Service public class BizService { // 使用多个参数组成key @Lock4j(keys = {"#userId", "#orderId"}) public void processOrder(Long userId, String orderId) { // 业务逻辑 } // 使用对象属性 @Lock4j(keys = {"#user.id", "#user.name"}) public void updateUser(@Param("user") User user) { // 业务逻辑 } // 自定义key前缀 @Lock4j(name = "order:lock", keys = {"#orderId"}) public void handleOrder(String orderId) { // 最终key: order:lock:orderId值 } }4. 手动获取锁
@Service public class ManualLockService { @Autowired private LockTemplate lockTemplate; public void doWithLock(String resourceId) { // 手动获取锁 LockInfo lockInfo = lockTemplate.lock(resourceId, 10000L, 3000L); if (lockInfo == null) { throw new RuntimeException("获取锁失败"); } try { // 业务逻辑 System.out.println("执行业务逻辑"); } finally { // 释放锁 lockTemplate.releaseLock(lockInfo); } } }5. 配合 LambdaQueryWrapper
@Service public class AccountService { @Autowired private AccountMapper accountMapper; @Lock4j(keys = {"#accountId"}, expire = 10000) @Transactional public void transfer(Long fromAccountId, Long toAccountId, BigDecimal amount) { // 使用 LambdaQueryWrapper 查询 LambdaQueryWrapper<Account> fromWrapper = Wrappers.<Account>lambdaQuery() .eq(Account::getId, fromAccountId); Account fromAccount = accountMapper.selectOne(fromWrapper); LambdaQueryWrapper<Account> toWrapper = Wrappers.<Account>lambdaQuery() .eq(Account::getId, toAccountId); Account toAccount = accountMapper.selectOne(toWrapper); // 扣款 fromAccount.setBalance(fromAccount.getBalance().subtract(amount)); accountMapper.updateById(fromAccount); // 加款 toAccount.setBalance(toAccount.getBalance().add(amount)); accountMapper.updateById(toAccount); } }五、高级配置
1. 自定义Key生成器
@Component public class CustomKeyGenerator implements LockKeyGenerator { @Override public String generateKey(LockInfo lockInfo, Method method, Object[] args) { // 自定义key生成逻辑 return "custom:" + method.getName() + ":" + Arrays.hashCode(args); } } // 使用方式 @Lock4j(keys = {"#id"}, keyGenerator = CustomKeyGenerator.class) public void customKeyMethod(Long id) { // ... }2. 自定义锁失败处理
@Component public class CustomLockFailureHandler implements LockFailureHandler { @Override public void onLockFailure(String key, Method method, Object[] args) { // 锁获取失败时的处理 throw new BusinessException("系统繁忙，请稍后重试"); } }3. 执行器配置
@Configuration public class Lock4jConfig { @Bean public ExecutorService lockExecutor() { return Executors.newFixedThreadPool(10); } }六、注意事项
1. 事务与锁的顺序
// ✅ 正确：锁在外，事务在内 @Lock4j(keys = {"#id"}) @Transactional public void correctWay(Long id) { // 业务逻辑 } // ❌ 错误：事务在外，锁在内可能导致事务未提交锁已释放 @Transactional @Lock4j(keys = {"#id"}) public void wrongWay(Long id) { // 业务逻辑 }2. 避免死锁
// 多个锁时注意顺序 @Lock4j(keys = {"#id1"}) public void method1(Long id1, Long id2) { // 调用需要锁id2的方法 - 可能导致死锁 method2(id2); } @Lock4j(keys = {"#id2"}) public void method2(Long id2) { // ... }3. 合理设置超时时间
lock4j: # 根据业务执行时间设置，建议比业务执行时间长30% expire: 5000 # 业务平均执行3秒，设置5秒 # 获取锁超时时间不宜过长 acquire-timeout: 2000七、常见问题解决
1. 锁未释放问题
// 使用 try-finally 确保释放 LockInfo lockInfo = lockTemplate.lock(key, 10000, 3000); try { // 业务操作 // 注意：不要在业务代码中提前return } finally { if (lockInfo != null) { lockTemplate.releaseLock(lockInfo); } }2. 重试机制
@Component public class RetryLockService { @Autowired private LockTemplate lockTemplate; public void executeWithRetry(String key, Runnable task, int maxRetries) { for (int i = 0; i < maxRetries; i++) { LockInfo lockInfo = lockTemplate.lock(key, 10000, 3000); if (lockInfo != null) { try { task.run(); return; } finally { lockTemplate.releaseLock(lockInfo); } } // 等待后重试 try { Thread.sleep(100); } catch (InterruptedException e) { Thread.currentThread().interrupt(); throw new RuntimeException(e); } } throw new RuntimeException("获取锁失败，重试" + maxRetries + "次"); } }八、性能优化建议
锁粒度：尽量使用细粒度锁，如按订单ID、用户ID
超时设置：根据业务耗时合理设置，避免过长或过短
监控告警：添加锁等待时间、失败率的监控
降级方案：锁服务不可用时，考虑本地锁或限流
九、最佳实践总结
@Service @Slf4j public class BestPracticeService { /** * 推荐的最佳实践模板 */ @Lock4j( keys = {"#bizId"}, // 精确的锁key expire = 10000, // 比业务执行时间长30-50% acquireTimeout = 2000 // 合理等待时间 ) @Transactional(rollbackFor = Exception.class) public Result doBusiness(String bizId, BusinessData data) { // 1. 参数校验 if (StringUtils.isEmpty(bizId)) { throw new IllegalArgumentException("业务ID不能为空"); } // 2. 业务处理 try { // MyBatis-Plus 数据库操作 return Result.success(); } catch (Exception e) { log.error("业务处理失败, bizId: {}", bizId, e); throw new BusinessException("处理失败"); } } }
