小编给大家分享一下Redis中如何实现支持几乎所有加锁场景的分布式锁，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！
<dependency> <groupId>org.redisson</groupId> <artifactId>redisson</artifactId> <version>3.16.2</version> </dependency>Copy to clipboardErrorCopied
/**
* 分布式锁自定义注解
*/
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Lock {
/**
* 锁的模式：如果不设置自动模式，当参数只有一个.使用 REENTRANT 参数多个 MULTIPLE
*/
LockModel lockModel() default LockModel.AUTO;
/**
* 如果keys有多个，如果不设置，则使用 联锁
*
* @return
*/
String[] keys() default {};
/**
* key的静态常量：当key的spel的值是LIST、数组时使用+号连接将会被spel认为这个变量是个字符串，只能产生一把锁，达不到我们的目的，
* 而我们如果又需要一个常量的话。这个参数将会在拼接在每个元素的后面
*
* @return
*/
String keyConstant() default "";
/**
* 锁超时时间,默认30000毫秒(可在配置文件全局设置)
*
* @return
*/
long watchDogTimeout() default 30000;
/**
* 等待加锁超时时间，默认10000毫秒 -1 则表示一直等待(可在配置文件全局设置)
*
* @return
*/
long attemptTimeout() default 10000;
}/**
* Redisson常量类
*/
public class RedissonConst {
/**
* redisson锁默认前缀
*/
public static final String REDISSON_LOCK = "redisson:lock:";
/**
* spel表达式占位符
*/
public static final String PLACE_HOLDER = "#";
}/**
* 锁的模式
*/
public enum LockModel {
/**
* 可重入锁
*/
REENTRANT,
/**
* 公平锁
*/
FAIR,
/**
* 联锁
*/
MULTIPLE,
/**
* 红锁
*/
RED_LOCK,
/**
* 读锁
*/
READ,
/**
* 写锁
*/
WRITE,
/**
* 自动模式，当参数只有一个使用 REENTRANT 参数多个 RED_LOCK
*/
AUTO
}/**
* 分布式锁异常
*/
public class ReddissonException extends RuntimeException {
public ReddissonException() {
}
public ReddissonException(String message) {
super(message);
}
public ReddissonException(String message, Throwable cause) {
super(message, cause);
}
public ReddissonException(Throwable cause) {
super(cause);
}
public ReddissonException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
super(message, cause, enableSuppression, writableStackTrace);
}
} /**
* 分布式锁aop
*/
@Slf4j
@Aspect
public class LockAop {
@Autowired
private RedissonClient redissonClient;
@Autowired
private RedissonProperties redissonProperties;
@Autowired
private LockStrategyFactory lockStrategyFactory;
@Around("@annotation(lock)")
public Object aroundAdvice(ProceedingJoinPoint proceedingJoinPoint, Lock lock) throws Throwable {
// 需要加锁的key数组
String[] keys = lock.keys();
if (ArrayUtil.isEmpty(keys)) {
throw new ReddissonException("redisson lock keys不能为空");
}
// 获取方法的参数名
String[] parameterNames = new LocalVariableTableParameterNameDiscoverer().getParameterNames(((MethodSignature) proceedingJoinPoint.getSignature()).getMethod());
Object[] args = proceedingJoinPoint.getArgs();
// 等待锁的超时时间
long attemptTimeout = lock.attemptTimeout();
if (attemptTimeout == 0) {
attemptTimeout = redissonProperties.getAttemptTimeout();
}
// 锁超时时间
long lockWatchdogTimeout = lock.watchdogTimeout();
if (lockWatchdogTimeout == 0) {
lockWatchdogTimeout = redissonProperties.getLockWatchdogTimeout();
}
// 加锁模式
LockModel lockModel = getLockModel(lock, keys);
if (!lockModel.equals(LockModel.MULTIPLE) && !lockModel.equals(LockModel.RED_LOCK) && keys.length > 1) {
throw new ReddissonException("参数有多个，锁模式为->" + lockModel.name() + "，无法匹配加锁");
}
log.info("锁模式->{}，等待锁定时间->{}毫秒，锁定最长时间->{}毫秒", lockModel.name(), attemptTimeout, lockWatchdogTimeout);
boolean res = false;
// 策略模式获取redisson锁对象
RLock rLock = lockStrategyFactory.createLock(lockModel, keys, parameterNames, args, lock.keyConstant(), redissonClient);
//执行aop
if (rLock != null) {
try {
if (attemptTimeout == -1) {
res = true;
//一直等待加锁
rLock.lock(lockWatchdogTimeout, TimeUnit.MILLISECONDS);
} else {
res = rLock.tryLock(attemptTimeout, lockWatchdogTimeout, TimeUnit.MILLISECONDS);
}
if (res) {
return proceedingJoinPoint.proceed();
} else {
throw new ReddissonException("获取锁失败");
}
} finally {
if (res) {
rLock.unlock();
}
}
}
throw new ReddissonException("获取锁失败");
}
/**
* 获取加锁模式
*
* @param lock
* @param keys
* @return
*/
private LockModel getLockModel(Lock lock, String[] keys) {
LockModel lockModel = lock.lockModel();
// 自动模式：优先匹配全局配置，再判断用红锁还是可重入锁
if (lockModel.equals(LockModel.AUTO)) {
LockModel globalLockModel = redissonProperties.getLockModel();
if (globalLockModel != null) {
lockModel = globalLockModel;
} else if (keys.length > 1) {
lockModel = LockModel.RED_LOCK;
} else {
lockModel = LockModel.REENTRANT;
}
}
return lockModel;
}
}这里使用了策略模式来对不同的锁类型提供实现。
先定义锁策略的抽象基类（也可以用接口）：
/**
* 锁策略抽象基类
*/
@Slf4j
abstract class LockStrategy {
@Autowired
private RedissonClient redissonClient;
/**
* 创建RLock
*
* @param keys
* @param parameterNames
* @param args
* @param keyConstant
* @return
*/
abstract RLock createLock(String[] keys, String[] parameterNames, Object[] args, String keyConstant, RedissonClient redissonClient);
/**
* 获取RLock
*
* @param keys
* @param parameterNames
* @param args
* @param keyConstant
* @return
*/
public RLock[] getRLocks(String[] keys, String[] parameterNames, Object[] args, String keyConstant) {
List<RLock> rLocks = new ArrayList<>();
for (String key : keys) {
List<String> valueBySpel = getValueBySpel(key, parameterNames, args, keyConstant);
for (String s : valueBySpel) {
rLocks.add(redissonClient.getLock(s));
}
}
RLock[] locks = new RLock[rLocks.size()];
int index = 0;
for (RLock r : rLocks) {
locks[index++] = r;
}
return locks;
}
/**
* 通过spring Spel 获取参数
*
* @param key 定义的key值 以#开头 例如:#user
* @param parameterNames 形参
* @param args 形参值
* @param keyConstant key的常亮
* @return
*/
List<String> getValueBySpel(String key, String[] parameterNames, Object[] args, String keyConstant) {
List<String> keys = new ArrayList<>();
if (!key.contains(PLACE_HOLDER)) {
String s = REDISSON_LOCK + key + keyConstant;
log.info("没有使用spel表达式value->{}", s);
keys.add(s);
return keys;
}
// spel解析器
ExpressionParser parser = new SpelExpressionParser();
// spel上下文
EvaluationContext context = new StandardEvaluationContext();
for (int i = 0; i < parameterNames.length; i++) {
context.setVariable(parameterNames[i], args[i]);
}
Expression expression = parser.parseExpression(key);
Object value = expression.getValue(context);
if (value != null) {
if (value instanceof List) {
List valueList = (List) value;
for (Object o : valueList) {
keys.add(REDISSON_LOCK + o.toString() + keyConstant);
}
} else if (value.getClass().isArray()) {
Object[] objects = (Object[]) value;
for (Object o : objects) {
keys.add(REDISSON_LOCK + o.toString() + keyConstant);
}
} else {
keys.add(REDISSON_LOCK + value.toString() + keyConstant);
}
}
log.info("spel表达式key={},value={}", key, keys);
return keys;
}
}再提供各种锁模式的具体实现：
可重入锁：
/**
* 可重入锁策略
*/
public class ReentrantLockStrategy extends LockStrategy {
@Override
public RLock createLock(String[] keys, String[] parameterNames, Object[] args, String keyConstant, RedissonClient redissonClient) {
List<String> valueBySpel = getValueBySpel(keys[0], parameterNames, args, keyConstant);
//如果spel表达式是数组或者集合 则使用红锁
if (valueBySpel.size() == 1) {
return redissonClient.getLock(valueBySpel.get(0));
} else {
RLock[] locks = new RLock[valueBySpel.size()];
int index = 0;
for (String s : valueBySpel) {
locks[index++] = redissonClient.getLock(s);
}
return new RedissonRedLock(locks);
}
}
}公平锁：
/**
* 公平锁策略
*/
public class FairLockStrategy extends LockStrategy {
@Override
public RLock createLock(String[] keys, String[] parameterNames, Object[] args, String keyConstant, RedissonClient redissonClient) {
return redissonClient.getFairLock(getValueBySpel(keys[0], parameterNames, args, keyConstant).get(0));
}
}联锁
/**
* 联锁策略
*/
public class MultipleLockStrategy extends LockStrategy {
@Override
public RLock createLock(String[] keys, String[] parameterNames, Object[] args, String keyConstant, RedissonClient redissonClient) {
RLock[] locks = getRLocks(keys, parameterNames, args, keyConstant);
return new RedissonMultiLock(locks);
}
}红锁
/**
* 红锁策略
*/
public class RedLockStrategy extends LockStrategy {
@Override
public RLock createLock(String[] keys, String[] parameterNames, Object[] args, String keyConstant, RedissonClient redissonClient) {
RLock[] locks = getRLocks(keys, parameterNames, args, keyConstant);
return new RedissonRedLock(locks);
}
}读锁
/**
* 读锁策略
*/
public class ReadLockStrategy extends LockStrategy {
@Override
public RLock createLock(String[] keys, String[] parameterNames, Object[] args, String keyConstant, RedissonClient redissonClient) {
RReadWriteLock rwLock = redissonClient.getReadWriteLock(getValueBySpel(keys[0], parameterNames, args, keyConstant).get(0));
return rwLock.readLock();
}
}写锁
/**
* 写锁策略
*/
public class WriteLockStrategy extends LockStrategy {
@Override
public RLock createLock(String[] keys, String[] parameterNames, Object[] args, String keyConstant, RedissonClient redissonClient) {
RReadWriteLock rwLock = redissonClient.getReadWriteLock(getValueBySpel(keys[0], parameterNames, args, keyConstant).get(0));
return rwLock.writeLock();
}
}最后提供一个策略工厂初始化锁策略：
/**
* 锁的策略工厂
*/
@Service
public class LockStrategyFactory {
private LockStrategyFactory() {
}
private static final Map<LockModel, LockStrategy> STRATEGIES = new HashMap<>(6);
static {
STRATEGIES.put(LockModel.FAIR, new FairLockStrategy());
STRATEGIES.put(LockModel.REENTRANT, new ReentrantLockStrategy());
STRATEGIES.put(LockModel.RED_LOCK, new RedLockStrategy());
STRATEGIES.put(LockModel.READ, new ReadLockStrategy());
STRATEGIES.put(LockModel.WRITE, new WriteLockStrategy());
STRATEGIES.put(LockModel.MULTIPLE, new MultipleLockStrategy());
}
public RLock createLock(LockModel lockModel, String[] keys, String[] parameterNames, Object[] args, String keyConstant, RedissonClient redissonClient) {
return STRATEGIES.get(lockModel).createLock(keys, parameterNames, args, keyConstant, redissonClient);
}
} @Lock(keys = "#query.channel") // 支持spel
@ApiOperation("分页列表")
@GetMapping
public ApiPageResult list(VendorProjectItemQuery query, Pagination pagination) {
return ApiPageResult.success(pagination, vendorProjectItemService.list(query, pagination), vendorProjectItemService.count(query));
}以上是“Redis中如何实现支持几乎所有加锁场景的分布式锁”这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注亿速云行业资讯频道！
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