使用Redisson实现分布式锁，Spring AOP简化之

Posted 2020-10-13 sprinkle

源码

Redisson概述

Redisson是一个在Redis的基础上实现的Java驻内存数据网格（In-Memory Data Grid）。它不仅提供了一系列的分布式的Java常用对象，还提供了许多分布式服务。其中包括(BitSet, Set, Multimap, SortedSet, Map, List, Queue, BlockingQueue, Deque, BlockingDeque, Semaphore, Lock, AtomicLong, CountDownLatch, Publish / Subscribe, Bloom filter, Remote service, Spring cache, Executor service, Live Object service, Scheduler service) Redisson提供了使用Redis的最简单和最便捷的方法。Redisson的宗旨是促进使用者对Redis的关注分离（Separation of Concern），从而让使用者能够将精力更集中地放在处理业务逻辑上。

Redisson底层采用的是Netty 框架。支持Redis 2.8以上版本，支持Java1.6+以上版本。

关于Redisson更多详细介绍，可参考Redssion概述

Redisson提供的分布式锁

可重入锁

Redisson的分布式可重入锁RLock Java对象实现了java.util.concurrent.locks.Lock接口，同时还支持自动过期解锁。下面是RLock的基本使用方法：

RLock lock = redisson.getLock("anyLock");
// 最常见的使用方法
lock.lock();

// 支持过期解锁功能
// 10秒钟以后自动解锁
// 无需调用unlock方法手动解锁
lock.lock(10, TimeUnit.SECONDS);

// 尝试加锁，最多等待100秒，上锁以后10秒自动解锁
boolean res = lock.tryLock(100, 10, TimeUnit.SECONDS);
...
lock.unlock();

Redisson同时还为分布式锁提供了异步执行的相关方法：

RLock lock = redisson.getLock("anyLock");
lock.lockAsync();
lock.lockAsync(10, TimeUnit.SECONDS);
Future<Boolean> res = lock.tryLockAsync(100, 10, TimeUnit.SECONDS);

公平锁

Redisson分布式可重入公平锁也是实现了java.util.concurrent.locks.Lock接口的一种RLock对象。在提供了自动过期解锁功能的同时，保证了当多个Redisson客户端线程同时请求加锁时，优先分配给先发出请求的线程。

RLock fairLock = redisson.getFairLock("anyLock");
// 最常见的使用方法
fairLock.lock();

// 支持过期解锁功能
// 10秒钟以后自动解锁
// 无需调用unlock方法手动解锁
fairLock.lock(10, TimeUnit.SECONDS);

// 尝试加锁，最多等待100秒，上锁以后10秒自动解锁
boolean res = fairLock.tryLock(100, 10, TimeUnit.SECONDS);
...
fairLock.unlock();

其他锁

Redisson还提供了其他机制的锁，如联锁(MultiLock)、红锁(RedLock)等。详细可参考：分布式锁和同步器

使用Redisson实现分布式锁

1. 定义回调接口

/**
 * 分布式锁回调接口
 */
public interface DistributedLockCallback<T> {
    /**
     * 调用者必须在此方法中实现需要加分布式锁的业务逻辑
     *
     * @return
     */
    public T process();

    /**
     * 得到分布式锁名称
     *
     * @return
     */
    public String getLockName();
}

2. 定义分布式锁模板

/**
 * 分布式锁操作模板
 */
public interface DistributedLockTemplate {

    long DEFAULT_WAIT_TIME = 30;
    long DEFAULT_TIMEOUT   = 5;
    TimeUnit DEFAULT_TIME_UNIT = TimeUnit.SECONDS;

    /**
     * 使用分布式锁，使用锁默认超时时间。
     * @param callback
     * @param fairLock 是否使用公平锁
     * @return
     */
    <T> T lock(DistributedLockCallback<T> callback, boolean fairLock);

    /**
     * 使用分布式锁。自定义锁的超时时间
     *
     * @param callback
     * @param leaseTime 锁超时时间。超时后自动释放锁。
     * @param timeUnit
     * @param fairLock 是否使用公平锁
     * @param <T>
     * @return
     */
    <T> T lock(DistributedLockCallback<T> callback, long leaseTime, TimeUnit timeUnit, boolean fairLock);

    /**
     * 尝试分布式锁，使用锁默认等待时间、超时时间。
     * @param callback
     * @param fairLock 是否使用公平锁
     * @param <T>
     * @return
     */
    <T> T tryLock(DistributedLockCallback<T> callback, boolean fairLock);

    /**
     * 尝试分布式锁，自定义等待时间、超时时间。
     * @param callback
     * @param waitTime 获取锁最长等待时间
     * @param leaseTime 锁超时时间。超时后自动释放锁。
     * @param timeUnit
     * @param fairLock 是否使用公平锁
     * @param <T>
     * @return
     */
    <T> T tryLock(DistributedLockCallback<T> callback, long waitTime, long leaseTime, TimeUnit timeUnit, boolean fairLock);
}

3. 实现分布式锁模板

public class SingleDistributedLockTemplate implements DistributedLockTemplate {
    private RedissonClient redisson;

    public SingleDistributedLockTemplate() {
    }

    public SingleDistributedLockTemplate(RedissonClient redisson) {
        this.redisson = redisson;
    }

    @Override
    public <T> T lock(DistributedLockCallback<T> callback, boolean fairLock) {
        return lock(callback, DEFAULT_TIMEOUT, DEFAULT_TIME_UNIT, fairLock);
    }

    @Override
    public <T> T lock(DistributedLockCallback<T> callback, long leaseTime, TimeUnit timeUnit, boolean fairLock) {
        RLock lock = getLock(redisson, callback.getLockName(), fairLock);
        try {
            lock.lock(leaseTime, timeUnit);
            return callback.process();
        } finally {
            if (lock != null) {
                lock.unlock();
            }
        }
    }

    @Override
    public <T> T tryLock(DistributedLockCallback<T> callback, boolean fairLock) {
        return tryLock(callback, DEFAULT_WAIT_TIME, DEFAULT_TIMEOUT, DEFAULT_TIME_UNIT, fairLock);
    }

    @Override
    public <T> T tryLock(DistributedLockCallback<T> callback, long waitTime, long leaseTime, TimeUnit timeUnit, boolean fairLock) {
        RLock lock = getLock(redisson, callback.getLockName(), fairLock);
        try {
            if (lock.tryLock(waitTime, leaseTime, timeUnit)) {
                return callback.process();
            }
        } catch (InterruptedException e) {

        } finally {
            if (lock != null) {
                lock.unlock();
            }
        }
        return null;
    }

    private RLock getLock(RedissonClient redisson, String lockName, boolean fairLock) {
        RLock lock;
        if (fairLock) {
            lock = redisson.getFairLock(lockName);
        } else {
            lock = redisson.getLock(lockName);
        }
        return lock;
    }

    public void setRedisson(RedissonClient redisson) {
        this.redisson = redisson;
    }
}

4. 使用SingleDistributedLockTemplate

DistributedLockTemplate lockTemplate = ...;
final String lockName = ...; 
lockTemplate.lock(new DistributedLockCallback<Object>() {
    @Override
    public Object process() {
        //do some business
        return null;
    }

    @Override
    public String getLockName() {
        return lockName;
    }
}, false);

但是每次使用分布式锁都要写类似上面的重复代码，有没有什么方法可以只关注核心业务逻辑代码的编写，即上面的"do some business"。下面介绍如何使用Spring AOP来实现这一目标。

使用Spring AOP简化分布式锁

1. 定义注解@DistributedLock

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DistributedLock {

    String lockName() default "";

    String lockNamePre() default ""; //lockName后缀

    String lockNamePost() default ""; //lockName后缀

    String param() default ""; //获取注解的方法第一个参数对象的某个属性值来作为lockName。因为有时候lockName是不固定的。

    boolean fairLock() default false;  //是否使用公平锁。

    boolean tryLock() default false;  //是否使用尝试锁。

    long waitTime() default 30L;

    long leaseTime() default 5L;

    TimeUnit timeUnit() default TimeUnit.SECONDS;

}

2. 定义切面织入的代码

@Aspect
@Component
public class DistributedLockAspect {

    @Autowired
    private DistributedLockTemplate lockTemplate;

    @Pointcut("@annotation(cn.sprinkle.study.distributedlock.common.annotation.DistributedLock)")
    public void DistributedLockAspect() {}



    @Around(value = "DistributedLockAspect()")
    public Object doAround(ProceedingJoinPoint pjp) throws Throwable {

        //切点所在的类名
        String targetName = pjp.getTarget().getClass().getName();

        //使用了注解的方法
        String methodName = pjp.getSignature().getName();

        Class targetClass = Class.forName(targetName);

        Method[] methods = targetClass.getMethods();

        Object[] arguments = pjp.getArgs();

        //得到使用注解的方法。可使用Method.getAnnotation(Class<T> annotationClass)获取指定的注解，然后可获得注解的属性
        Optional<Method> optional = Arrays.stream(methods)
                .parallel()
                .filter(method -> method.getName().equals(methodName))
                .findAny();

        if (optional.isPresent()) {
            Method m = optional.get();
            final String lockName = getLockName(m, arguments);
            return lock(pjp, m, lockName);
        }

        return null;
    }

    public String getLockName(Method method, Object[] args) throws Throwable {

        DistributedLock annotation = method.getAnnotation(DistributedLock.class);

        String lockName = annotation.lockName(),
                param = annotation.param();

        if (StringUtils.isEmpty(lockName)) {
            if (!StringUtils.isEmpty(param)) {

                if (args.length > 0) {
                    Object arg = args[0];

                    lockName = String.valueOf(getParam(arg, param));

                    String preLockName = annotation.lockNamePre(),
                            postLockName = annotation.lockNamePost();

                    lockName = preLockName + lockName + postLockName;

                    return lockName;
                }
            }
        } else {
            return lockName;
        }

        throw new IllegalArgumentException("lockName can‘t be empty!");
    }

    /**
     * 从方法参数获取数据
     *
     * @param param
     * @param arg 方法的参数数组
     * @return
     */
    public Object getParam(Object arg, String param) throws Throwable {

        if (!StringUtils.isEmpty(param) && arg != null) {
            Object result = PropertyUtils.getProperty(arg, param);
            return result;
        }

        return null;
    }

    public Object lock(ProceedingJoinPoint pjp, Method method, final String lockName) {

        DistributedLock annotation = method.getAnnotation(DistributedLock.class);

        boolean fairLock = annotation.fairLock();

        boolean tryLock = annotation.tryLock();

        if (tryLock) {
            return tryLock(pjp, annotation, lockName, fairLock);
        } else {
            return lock(pjp,lockName, fairLock);
        }
    }

    public Object lock(ProceedingJoinPoint pjp, final String lockName, boolean fairLock) {
        return lockTemplate.lock(new DistributedLockCallback<Object>() {
            @Override
            public Object process() {
                return proceed(pjp);
            }

            @Override
            public String getLockName() {
                return lockName;
            }
        }, fairLock);
    }

    public Object tryLock(ProceedingJoinPoint pjp, DistributedLock annotation, final String lockName, boolean fairLock) {

        long waitTime = annotation.waitTime(),
                leaseTime = annotation.leaseTime();
        TimeUnit timeUnit = annotation.timeUnit();

        return lockTemplate.tryLock(new DistributedLockCallback<Object>() {
            @Override
            public Object process() {
                return proceed(pjp);
            }

            @Override
            public String getLockName() {
                return lockName;
            }
        }, waitTime, leaseTime, timeUnit, fairLock);
    }

    public Object proceed(ProceedingJoinPoint pjp) {
        try {
            return pjp.proceed();
        } catch (Throwable throwable) {
            throwable.printStackTrace();
        }
        return null;
    }
}

3. 使用注解@DistributedLock实现分布式锁

有了上面两段代码，以后需要用到分布式锁，只需在核心业务逻辑方法添加注解@DistributedLock，并设置LockName、fairLock等即可。

@Service
public class DistributionService {

    @Autowired
    private RedissonClient redissonClient;

    @DistributedLock(lockName = "lock", lockNamePost = ".lock")
    public Integer aspect() {
        RMap<String, Integer> map = redissonClient.getMap("distributionTest");

        Integer count = map.get("count");

        if (count > 0) {
            count = count - 1;
            map.put("count", count);
        }

        return count;
    }

    @DistributedLock(param = "id", lockNamePost = ".lock")
    public Integer aspect(Person person) {
        RMap<String, Integer> map = redissonClient.getMap("distributionTest");

        Integer count = map.get("count");

        if (count > 0) {
            count = count - 1;
            map.put("count", count);
        }

        return count;
    }

}

4. 测试

定义一个Worker类：

public class Worker implements Runnable {

    private final CountDownLatch startSignal;
    private final CountDownLatch doneSignal;
    private final DistributionService service;

    public Worker(CountDownLatch startSignal, CountDownLatch doneSignal, DistributionService service) {
        this.startSignal = startSignal;
        this.doneSignal = doneSignal;
        this.service = service;
    }

    @Override
    public void run() {
        try {
            startSignal.await();

            System.out.println(Thread.currentThread().getName() + " start");

            //Integer count = service.aspect();
            Integer count = service.aspect(new Person(1, "张三"));

            System.out.println(Thread.currentThread().getName() + ": count = " + count);

            doneSignal.countDown();

        } catch (InterruptedException ex) {
            System.out.println(ex);
        }
    }
}

定义Controller类：

@RestController
@RequestMapping("/distributedLockTest")
public class DistributedLockTestController {

    private int count = 10;

    @Autowired
    private RedissonClient redissonClient;

    @Autowired
    private DistributionService service;

    @RequestMapping(method = RequestMethod.GET)
    public String distributedLockTest() throws Exception {

        RMap<String, Integer> map = redissonClient.getMap("distributionTest");
        map.put("count", 8);

        CountDownLatch startSignal = new CountDownLatch(1);
        CountDownLatch doneSignal = new CountDownLatch(count);

        for (int i = 0; i < count; ++i) { // create and start threads
            new Thread(new Worker(startSignal, doneSignal, service)).start();
        }

        startSignal.countDown(); // let all threads proceed
        doneSignal.await();
        System.out.println("All processors done. Shutdown connection");

        return "finish";
    }

}

Redisson基本配置：

singleServerConfig:
  idleConnectionTimeout: 10000
  pingTimeout: 1000
  connectTimeout: 10000
  timeout: 3000
  retryAttempts: 3
  retryInterval: 1500
  reconnectionTimeout: 3000
  failedAttempts: 3
  password:
  subscriptionsPerConnection: 5
  clientName: null
  address: "redis://127.0.0.1:6379"
  subscriptionConnectionMinimumIdleSize: 1
  subscriptionConnectionPoolSize: 50
  connectionMinimumIdleSize: 10
  connectionPoolSize: 64
  database: 0
  dnsMonitoring: false
  dnsMonitoringInterval: 5000
threads: 0
nettyThreads: 0
codec: !<org.redisson.codec.JsonJacksonCodec> {}
useLinuxNativeEpoll: false

工程中需要注入的对象：

@Value("classpath:/redisson-conf.yml")
Resource configFile;

@Bean(destroyMethod = "shutdown")
RedissonClient redisson()
        throws IOException {
    Config config = Config.fromYAML(configFile.getInputStream());
    return Redisson.create(config);
}

@Bean
DistributedLockTemplate distributedLockTemplate(RedissonClient redissonClient) {
    return new SingleDistributedLockTemplate(redissonClient);
}

需要引入的依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-aop</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.redisson</groupId>
    <artifactId>redisson</artifactId>
    <version>3.5.3</version>
</dependency>
<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.8.3</version>
</dependency>

最后启动工程，然后访问localhost:8080/distributedLockTest，可以看到如下结果：

观察结果，可以看出，10个线程中只有8个线程能执行count减1操作，而且多个线程是依次执行的。也就是说分布式锁起作用了。

至此，使用Redisson实现分布式锁，然后使用Spring AOP简化分布式锁介绍完毕。

 

若有什么地方有错误的或需要改进的，欢迎留言一起讨论交流。