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ReentrantLock 的典型使用场景和实现方法

news 2026/5/11 20:29:21

基本概念

ReentrantLock 是 Java 幑发包中提供的可重入互斥锁，相比 synchronized 关键字提供了更高的灵活性和功能。

典型使用场景

1. 防止重复提交

防止用户重复点击按钮导致的重复业务处理。

2. 缓存双检锁机制

在缓存失效时，防止多个线程同时重建缓存。

3. 资源竞争控制

对共享资源的访问进行精确控制。

4. 定时任务并发控制

确保同一时刻只有一个定时任务实例运行。

实现方法

方法一：在 Service 层直接使用

@Service
public class BusinessService {private final ReentrantLock lock = new ReentrantLock();public void processBusinessLogic(String key) {lock.lock();try {// 执行核心业务逻辑doSomething(key);} finally {lock.unlock();}}private void doSomething(String key) {// 具体业务实现}
}

方法二：使用静态 Map 管理多个锁

@Service
public class MultiKeyService {private static final Map<String, ReentrantLock> lockMap = new ConcurrentHashMap<>();public void processByKey(String key) {ReentrantLock lock = lockMap.computeIfAbsent(key, k -> new ReentrantLock());lock.lock();try {// 处理特定 key 的业务逻辑handleBusiness(key);} finally {lock.unlock();}}private void handleBusiness(String key) {// 具体业务实现}
}

方法三：封装为工具类使用

@Component
public class LockUtil {private static final Map<String, ReentrantLock> lockMap = new ConcurrentHashMap<>();public <T> T executeWithLock(String key, Supplier<T> supplier) {ReentrantLock lock = lockMap.computeIfAbsent(key, k -> new ReentrantLock());lock.lock();try {return supplier.get();} finally {lock.unlock();}}public void executeWithLock(String key, Runnable runnable) {ReentrantLock lock = lockMap.computeIfAbsent(key, k -> new ReentrantLock());lock.lock();try {runnable.run();} finally {lock.unlock();}}
}// 使用示例
@Service
public class BusinessService {@Autowiredprivate LockUtil lockUtil;public void processData(String key) {lockUtil.executeWithLock(key, () -> {// 执行业务逻辑doProcess(key);});}
}

方法四：使用 tryLock 避免阻塞

@Service
public class TimeoutControlService {private final ReentrantLock lock = new ReentrantLock();public boolean processWithTimeout() {try {if (lock.tryLock(3, TimeUnit.SECONDS)) {try {// 执行业务逻辑doProcess();return true;} finally {lock.unlock();}}} catch (InterruptedException e) {Thread.currentThread().interrupt();}return false;}private void doProcess() {// 具体业务实现}
}

在 Spring Bean 中的注意事项

1. 锁的作用域

@Service
public class SingletonService {// 实例变量 - 同一个锁对象private final ReentrantLock lock = new ReentrantLock();// 每次调用创建新锁 - 锁失效// private ReentrantLock getLock() { return new ReentrantLock(); }
}

2. 异常处理

@Service
public class ExceptionSafeService {private final ReentrantLock lock = new ReentrantLock();public void safeProcess() {lock.lock();try {// 业务逻辑可能会抛出异常riskyOperation();} finally {// 必须在 finally 中释放锁lock.unlock();}}
}

与 @Transactional 结合使用的注意事项

@Service
public class TransactionalLockService {private final ReentrantLock lock = new ReentrantLock();// 推荐：先加锁后开启事务public void correctWay() {lock.lock();try {transactionalMethod();} finally {lock.unlock();}}@Transactionalpublic void transactionalMethod() {// 数据库操作}
}