# spring-boot-demo-zookeeper

> 此 demo 主要演示了如何使用 Spring Boot 集成 Zookeeper 结合AOP实现分布式锁。

## pom.xml

```xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <artifactId>spring-boot-demo-zookeeper</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>spring-boot-demo-zookeeper</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>com.xkcoding</groupId>
        <artifactId>spring-boot-demo</artifactId>
        <version>1.0.0-SNAPSHOT</version>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>
        </dependency>

        <!-- curator 版本4.1.0 对应 zookeeper 版本 3.5.x -->
        <!-- curator 与 zookeeper 版本对应关系：https://curator.apache.org/zk-compatibility.html -->
        <dependency>
            <groupId>org.apache.curator</groupId>
            <artifactId>curator-recipes</artifactId>
            <version>4.1.0</version>
        </dependency>

        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
    </dependencies>

    <build>
        <finalName>spring-boot-demo-zookeeper</finalName>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>
```

## ZkProps.java

```java
/**
 * <p>
 * Zookeeper 配置项
 * </p>
 *
 * @author yangkai.shen
 * @date Created in 2018-12-27 14:47
 */
@Data
@ConfigurationProperties(prefix = "zk")
public class ZkProps {
    /**
     * 连接地址
     */
    private String url;

    /**
     * 超时时间(毫秒)，默认1000
     */
    private int timeout = 1000;

    /**
     * 重试次数，默认3
     */
    private int retry = 3;
}
```

## application.yml

```yaml
server:
  port: 8080
  servlet:
    context-path: /demo

zk:
  url: 127.0.0.1:2181
  timeout: 1000
  retry: 3
```

## ZkConfig.java

```java
/**
 * <p>
 * Zookeeper配置类
 * </p>
 *
 * @author yangkai.shen
 * @date Created in 2018-12-27 14:45
 */
@Configuration
@EnableConfigurationProperties(ZkProps.class)
public class ZkConfig {
    private final ZkProps zkProps;

    @Autowired
    public ZkConfig(ZkProps zkProps) {
        this.zkProps = zkProps;
    }

    @Bean
    public CuratorFramework curatorFramework() {
        RetryPolicy retryPolicy = new ExponentialBackoffRetry(zkProps.getTimeout(), zkProps.getRetry());
        CuratorFramework client = CuratorFrameworkFactory.newClient(zkProps.getUrl(), retryPolicy);
        client.start();
        return client;
    }
}
```

## ZooLock.java

> 分布式锁的关键注解

```java
/**
 * <p>
 * 基于Zookeeper的分布式锁注解
 * 在需要加锁的方法上打上该注解后，AOP会帮助你统一管理这个方法的锁
 * </p>
 *
 * @author yangkai.shen
 * @date Created in 2018-12-27 14:11
 */
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface ZooLock {
    /**
     * 分布式锁的键
     */
    String key();

    /**
     * 锁释放时间，默认五秒
     */
    long timeout() default 5 * 1000;

    /**
     * 时间格式，默认：毫秒
     */
    TimeUnit timeUnit() default TimeUnit.MILLISECONDS;
}
```

## LockKeyParam.java

> 分布式锁动态key的关键注解

```java
/**
 * <p>
 * 分布式锁动态key注解，配置之后key的值会动态获取参数内容
 * </p>
 *
 * @author yangkai.shen
 * @date Created in 2018-12-27 14:17
 */
@Target({ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface LockKeyParam {
    /**
     * 如果动态key在user对象中，那么就需要设置fields的值为user对象中的属性名可以为多个，基本类型则不需要设置该值
     * <p>例1：public void count(@LockKeyParam({"id"}) User user)
     * <p>例2：public void count(@LockKeyParam({"id","userName"}) User user)
     * <p>例3：public void count(@LockKeyParam String userId)
     */
    String[] fields() default {};
}
```

## ZooLockAspect.java

> 分布式锁的关键部分

```java
/**
 * <p>
 * 使用 aop 切面记录请求日志信息
 * </p>
 *
 * @author yangkai.shen
 * @date Created in 2018-10-01 22:05
 */
@Aspect
@Component
@Slf4j
public class ZooLockAspect {
    private final CuratorFramework zkClient;

    private static final String KEY_PREFIX = "DISTRIBUTED_LOCK_";

    private static final String KEY_SEPARATOR = "/";

    @Autowired
    public ZooLockAspect(CuratorFramework zkClient) {
        this.zkClient = zkClient;
    }

    /**
     * 切入点
     */
    @Pointcut("@annotation(com.xkcoding.zookeeper.annotation.ZooLock)")
    public void doLock() {

    }

    /**
     * 环绕操作
     *
     * @param point 切入点
     * @return 原方法返回值
     * @throws Throwable 异常信息
     */
    @Around("doLock()")
    public Object around(ProceedingJoinPoint point) throws Throwable {
        MethodSignature signature = (MethodSignature) point.getSignature();
        Method method = signature.getMethod();
        Object[] args = point.getArgs();
        ZooLock zooLock = method.getAnnotation(ZooLock.class);
        if (StrUtil.isBlank(zooLock.key())) {
            throw new RuntimeException("分布式锁键不能为空");
        }
        String lockKey = buildLockKey(zooLock, method, args);
        InterProcessMutex lock = new InterProcessMutex(zkClient, lockKey);
        try {
            // 假设上锁成功，以后拿到的都是 false
            if (lock.acquire(zooLock.timeout(), zooLock.timeUnit())) {
                return point.proceed();
            } else {
                throw new RuntimeException("请勿重复提交");
            }
        } finally {
            lock.release();
        }
    }

    /**
     * 构造分布式锁的键
     *
     * @param lock   注解
     * @param method 注解标记的方法
     * @param args   方法上的参数
     * @return
     * @throws NoSuchFieldException
     * @throws IllegalAccessException
     */
    private String buildLockKey(ZooLock lock, Method method, Object[] args) throws NoSuchFieldException, IllegalAccessException {
        StringBuilder key = new StringBuilder(KEY_SEPARATOR + KEY_PREFIX + lock.key());

        // 迭代全部参数的注解，根据使用LockKeyParam的注解的参数所在的下标，来获取args中对应下标的参数值拼接到前半部分key上
        Annotation[][] parameterAnnotations = method.getParameterAnnotations();

        for (int i = 0; i < parameterAnnotations.length; i++) {
            // 循环该参数全部注解
            for (Annotation annotation : parameterAnnotations[i]) {
                // 注解不是 @LockKeyParam
                if (!annotation.annotationType().isInstance(LockKeyParam.class)) {
                    continue;
                }

                // 获取所有fields
                String[] fields = ((LockKeyParam) annotation).fields();
                if (ArrayUtil.isEmpty(fields)) {
                    // 普通数据类型直接拼接
                    if (ObjectUtil.isNull(args[i])) {
                        throw new RuntimeException("动态参数不能为null");
                    }
                    key.append(KEY_SEPARATOR).append(args[i]);
                } else {
                    // @LockKeyParam的fields值不为null，所以当前参数应该是对象类型
                    for (String field : fields) {
                        Class<?> clazz = args[i].getClass();
                        Field declaredField = clazz.getDeclaredField(field);
                        declaredField.setAccessible(true);
                        Object value = declaredField.get(clazz);
                        key.append(KEY_SEPARATOR).append(value);
                    }
                }
            }
        }
        return key.toString();
    }

}
```

## SpringBootDemoZookeeperApplicationTests.java

> 测试分布式锁

```java
@RunWith(SpringRunner.class)
@SpringBootTest
@Slf4j
public class SpringBootDemoZookeeperApplicationTests {

    public Integer getCount() {
        return count;
    }

    private Integer count = 10000;
    private ExecutorService executorService = Executors.newFixedThreadPool(1000);

    @Autowired
    private CuratorFramework zkClient;

    /**
     * 不使用分布式锁，程序结束查看count的值是否为0
     */
    @Test
    public void test() throws InterruptedException {
        IntStream.range(0, 10000).forEach(i -> executorService.execute(this::doBuy));
        TimeUnit.MINUTES.sleep(1);
        log.error("count值为{}", count);
    }

    /**
     * 测试AOP分布式锁
     */
    @Test
    public void testAopLock() throws InterruptedException {
        // 测试类中使用AOP需要手动代理
        SpringBootDemoZookeeperApplicationTests target = new SpringBootDemoZookeeperApplicationTests();
        AspectJProxyFactory factory = new AspectJProxyFactory(target);
        ZooLockAspect aspect = new ZooLockAspect(zkClient);
        factory.addAspect(aspect);
        SpringBootDemoZookeeperApplicationTests proxy = factory.getProxy();
        IntStream.range(0, 10000).forEach(i -> executorService.execute(() -> proxy.aopBuy(i)));
        TimeUnit.MINUTES.sleep(1);
        log.error("count值为{}", proxy.getCount());
    }

    /**
     * 测试手动加锁
     */
    @Test
    public void testManualLock() throws InterruptedException {
        IntStream.range(0, 10000).forEach(i -> executorService.execute(this::manualBuy));
        TimeUnit.MINUTES.sleep(1);
        log.error("count值为{}", count);
    }

    @ZooLock(key = "buy", timeout = 1, timeUnit = TimeUnit.MINUTES)
    public void aopBuy(int userId) {
        log.info("{} 正在出库。。。", userId);
        doBuy();
        log.info("{} 扣库存成功。。。", userId);
    }

    public void manualBuy() {
        String lockPath = "/buy";
        log.info("try to buy sth.");
        try {
            InterProcessMutex lock = new InterProcessMutex(zkClient, lockPath);
            try {
                if (lock.acquire(1, TimeUnit.MINUTES)) {
                    doBuy();
                    log.info("buy successfully!");
                }
            } finally {
                lock.release();
            }
        } catch (Exception e) {
            log.error("zk error");
        }
    }

    public void doBuy() {
        count--;
        log.info("count值为{}", count);
    }

}
```

## 参考

1. [如何在测试类中使用 AOP](https://stackoverflow.com/questions/11436600/unit-testing-spring-around-aop-methods)
2. zookeeper 实现分布式锁：《Spring Boot 2精髓 从构建小系统到架构分布式大系统》李家智 - 第16章 - Spring Boot 和 Zoo Keeper - 16.3 实现分布式锁
