1. What？
分布式锁，在分布式模型下，去争夺一个资源，先抢占资源的可以执行相关的业务逻辑，执行后再释放锁资源，未抢到锁资源的退出。
本文中利用redis（也可用mysql、zk等）实现
2. How？
利用spring aop实现分布式锁注解
@DLock，利用spring el实现幂等键
分布式锁使用示例：
@RestController
public class PingController {
@GetMapping("/ping")
// 添加分布式锁
@DLock(idempotentKeys = {"#id", "#type"})
public BaseResult ping(@DKeyAlias("id")String id,@DKeyAlias("type")String type) {
return Result.ok("hello world!");
}
}
AOP逻辑：
@Aspect
@Component
@Slf4j
public class DLockAspect {
@Autowired
private DLockManager DLockManager;
@Pointcut("@annotation(com.github.whvixd.panic.buying.model.annotation.DLock)")
public void dLockAspect() {
}
@Around("dLockAspect()")
public Object lockAround(ProceedingJoinPoint proceeding) {
DLockModel dLockModel = this.getDLockModel(proceeding);
// 获取分布式锁
boolean locked = this.getDLock(dLockModel);
if (locked) {
try {
return proceeding.proceed();
} catch (Throwable throwable) {
log.error("DLockAspect->lockAround error,message:{} ", throwable.getMessage(), throwable);
throw new BusinessException(BusinessExceptionCode.SYSTEM_ERROR.getErrorMessage(), throwable);
} finally {
if (dLockModel.getExpireType() == ExpireType.METHOD) {
// 删除锁
this.delLock(dLockModel);
}
}
} else {
log.info("DLockAspect->lockAround don't get dLock,threadName:{},dLockModel:{}", Thread.currentThread().getName(), dLockModel);
throw new BusinessException(BusinessExceptionCode.NOT_GET_LOCK.getErrorMessage(), dLockModel.getLockPrefix() + "->" + dLockModel.getLockKey());
}
}
/**
* 获取分布式锁
*/
private boolean getDLock(DLockModel dLockModel) {
if (dLockModel == null) {
return false;
}
String lockPrefix = dLockModel.getLockPrefix();
String lockKey = dLockModel.getLockKey();
String idempotentId = dLockModel.getIdempotentId();
int timeToLiveSeconds = dLockModel.getTimeToLiveSeconds();
if (StringUtils.isEmpty(lockPrefix) || StringUtils.isEmpty(lockKey)) {
log.warn("DLockAspect->getDLock check false,lockPrefix:{},lockKey:{}", lockPrefix, lockKey);
return false;
}
String redisKey = getRedisKey(lockPrefix, lockKey, idempotentId);
return DLockManager.setnx(redisKey, "1", timeToLiveSeconds);
}
/**
* 删除锁
*/
private void delLock(DLockModel dLockModel) {
if (dLockModel == null) {
return;
}
String lockPrefix = dLockModel.getLockPrefix();
String lockKey = dLockModel.getLockKey();
String idempotentId = dLockModel.getIdempotentId();
DLockManager.del(getRedisKey(lockPrefix, lockKey, idempotentId));
}
/**
* 获取锁参数
*/
private DLockModel getDLockModel(ProceedingJoinPoint proceeding) {
MethodSignature sign = (MethodSignature) proceeding.getSignature();
Method method = sign.getMethod();
DLock dLock = method.getAnnotation(DLock.class);
String lockPrefix = dLock.lockPrefix();
String lockKey = dLock.lockKey();
return DLockModel.builder()
.lockPrefix(StringUtils.isBlank(lockPrefix) ? method.getDeclaringClass().getSimpleName() : lockPrefix)
.lockKey(StringUtils.isBlank(lockKey) ? method.getName() : lockKey)
.timeToLiveSeconds(Long.valueOf(dLock.timeUnit().toSeconds(dLock.expireTime())).intValue())
.idempotentId(getIdempotentId(dLock.idempotentKeys(), proceeding.getArgs(), method.getParameters()))
.expireType(dLock.expireType())
.build();
}
/**
* 获取EvaluationContext，填充模板
*/
private EvaluationContext getEvaluationContext(Object[] args, Parameter[] parameters) {
EvaluationContext context = new StandardEvaluationContext();
IntStream.range(0, parameters.length).forEach(i -> {
Parameter parameter = parameters[i];
context.setVariable(getVariableName(parameter), args[i] == null ? StringUtils.EMPTY : args[i]);
});
return context;
}
/**
* 获取变量名称
*/
private String getVariableName(Parameter parameter) {
if (parameter == null) {
return StringUtils.EMPTY;
}
DKeyAlias annotation = parameter.getAnnotation(DKeyAlias.class);
return annotation == null ? parameter.getName() :
StringUtils.defaultIfBlank(annotation.value(), parameter.getName());
}
/**
* 拼接幂等id
*/
private String getIdempotentId(String[] idempotentKeys, Object[] args, Parameter[] parameters) {
if (!ObjectUtils.allNotNull(idempotentKeys, args, parameters)) {
return StringUtils.EMPTY;
}
EvaluationContext evaluationContext = getEvaluationContext(args, parameters);
StringBuilder builder = new StringBuilder();
for (String idempotentKey : idempotentKeys) {
String elValue = String.valueOf(getElValue(evaluationContext, idempotentKey));
if (StringUtils.isNotBlank(elValue)) {
builder.append(elValue).append(":");
}
}
String result = builder.toString();
return StringUtils.isNotBlank(result) ? SecureUtil.md5(result) : result;
}
/**
* 解析EL模板值
*/
private Object getElValue(EvaluationContext context, String idempotentKey) {
if (StringUtils.isBlank(idempotentKey) || context == null) {
return StringUtils.EMPTY;
}
ExpressionParser parser = new SpelExpressionParser();
Expression expression = parser.parseExpression(idempotentKey);
try {
return expression.getValue(context);
} catch (EvaluationException e) {
return StringUtils.EMPTY;
}
}
/**
* 获取redis key
*/
private String getRedisKey(String lockPrefix, String lockKey, String idempotentId) {
return lockPrefix + "-" + lockKey + (StringUtils.isNotBlank(idempotentId) ? "-" + idempotentId : StringUtils.EMPTY);
}
}
分布式锁管理器：
需实现者自行注入IoC容器中
public interface DLockManager {
boolean setnx(String redisKey, String value, int timeToLiveSeconds);
void del(String redisKey);
}
分布式锁管理器示例：
public class DLockClientManager implements DLockManager {
// 可使用redis、zk、mysql自行实现，本文中暂用本地cache实现
private Cache<String, Object> guavaCache = CacheBuilder.newBuilder().expireAfterWrite(5, TimeUnit.SECONDS).recordStats().initialCapacity(100).build();
@Override
public boolean setnx(String redisKey, String value, int timeToLiveSeconds) {
Object object = guavaCache.getIfPresent(redisKey);
if (object != null) {
return false;
}
guavaCache.put(redisKey, value);
log.info("RedisClientManager->setnx success,redisKey:{},value:{},timeToLiveSeconds:{}", redisKey, value, timeToLiveSeconds);
return true;
}
@Override
public void del(String redisKey) {
guavaCache.invalidate(redisKey);
log.info("RedisClientManager->del success,redisKey:{}", redisKey);
}
}
测试：
@RunWith(SpringRunner.class)
@SpringBootTest
@Slf4j
public class DLockAspectTest {
@Autowired
private PingController pingController;
@Test(expected = BusinessException.class)
public void lockAroundTest() throws InterruptedException {
// 占用锁资源时间默认为5s，使用者可配置化
pingController.ping();
log.info("-------");
pingController.ping();
Thread.sleep(10000L);
}
}
