前言

面试总是会被问到有没有用过分布式锁、redis 锁，大部分读者平时很少接触到，所以只能很无奈的回答 “没有”。本文通过 Spring Boot 整合 redisson 来实现分布式锁，并结合 demo 测试结果。

首先看下大佬总结的图

正文

添加依赖

<!--redis-->
<dependency>
<groupId>
org.springframework.boot
</groupId>
<artifactId>
spring-boot-starter-data-redis
</artifactId>
</dependency>
<!--redisson-->
<dependency>
<groupId>
org.redisson
</groupId>
<artifactId>
redisson-spring-boot-starter
</artifactId>
<version>
3.10.6
</version>
</dependency>

配置信息

spring:
# redis
  redis:
    host: 
47.103
.
5.190
    port: 
6379
    jedis:
      pool:
# 连接池最大连接数（使用负值表示没有限制）
        max-active: 100
# 连接池中的最小空闲连接
        max-idle: 10
# 连接池最大阻塞等待时间（使用负值表示没有限制）
        max-wait: -1
# 连接超时时间（毫秒）
      timeout: 5000
#默认是索引为0的数据库
      database: 0

配置类

/**
 * redisson 配置，下面是单节点配置：
 *
 * @author gourd
 */
@Configuration
publicclass
RedissonConfig
{
@Value
(
"${spring.redis.host}"
)
private
String
 host;
@Value
(
"${spring.redis.port}"
)
private
String
 port;
@Value
(
"${spring.redis.password:}"
)
private
String
 password;

@Bean
public
RedissonClient
 redissonClient() {
Config
 config = 
new
Config
();
//单节点
        config.useSingleServer().setAddress(
"redis://"
+ host + 
":"
+ port);
if
(
StringUtils
.isEmpty(password)) {
            config.useSingleServer().setPassword(
null
);
} 
else
{
            config.useSingleServer().setPassword(password);
}
//添加主从配置
// config.useMasterSlaveServers().setMasterAddress("").setPassword("").addSlaveAddress(new String[]{"",""});
// 集群模式配置 setScanInterval()扫描间隔时间，单位是毫秒, //可以用"rediss://"来启用SSL连接
// config.useClusterServers().setScanInterval(2000).addNodeAddress("redis://127.0.0.1:7000", "redis://127.0.0.1:7001").addNodeAddress("redis://127.0.0.1:7002");
return
Redisson
.create(config);
}
}

Redisson 工具类

/**
 * redis分布式锁帮助类
 *
 * @author gourd
 *
 */
publicclass
RedisLockUtil
{

privatestatic
DistributedLocker
 distributedLocker = 
SpringContextHolder
.getBean(
"distributedLocker"
,
DistributedLocker
.
class
);

/**
     * 加锁
     * @param lockKey
     * @return
     */
publicstatic
RLock
lock
(
String
 lockKey) {
return
 distributedLocker.
lock
(lockKey);
}

/**
     * 释放锁
     * @param lockKey
     */
publicstaticvoid
 unlock(
String
 lockKey) {
        distributedLocker.unlock(lockKey);
}

/**
     * 释放锁
     * @param lock
     */
publicstaticvoid
 unlock(
RLock
lock
) {
        distributedLocker.unlock(
lock
);
}

/**
     * 带超时的锁
     * @param lockKey
     * @param timeout 超时时间   单位：秒
     */
publicstatic
RLock
lock
(
String
 lockKey, 
int
 timeout) {
return
 distributedLocker.
lock
(lockKey, timeout);
}

/**
     * 带超时的锁
     * @param lockKey
     * @param unit 时间单位
     * @param timeout 超时时间
     */
publicstatic
RLock
lock
(
String
 lockKey, 
int
 timeout,
TimeUnit
 unit ) {
return
 distributedLocker.
lock
(lockKey, unit, timeout);
}

/**
     * 尝试获取锁
     * @param lockKey
     * @param waitTime 最多等待时间
     * @param leaseTime 上锁后自动释放锁时间
     * @return
     */
publicstaticboolean
 tryLock(
String
 lockKey, 
int
 waitTime, 
int
 leaseTime) {
return
 distributedLocker.tryLock(lockKey, 
TimeUnit
.SECONDS, waitTime, leaseTime);
}

/**
     * 尝试获取锁
     * @param lockKey
     * @param unit 时间单位
     * @param waitTime 最多等待时间
     * @param leaseTime 上锁后自动释放锁时间
     * @return
     */
publicstaticboolean
 tryLock(
String
 lockKey, 
TimeUnit
 unit, 
int
 waitTime, 
int
 leaseTime) {
return
 distributedLocker.tryLock(lockKey, unit, waitTime, leaseTime);
}

/**
     * 获取计数器
     *
     * @param name
     * @return
     */
publicstatic
RCountDownLatch
 getCountDownLatch(
String
 name){
return
 distributedLocker.getCountDownLatch(name);
}

/**
     * 获取信号量
     *
     * @param name
     * @return
     */
publicstatic
RSemaphore
 getSemaphore(
String
 name){
return
 distributedLocker.getSemaphore(name);
}
}

底层封装

/**
 * @author gourd
 */
publicinterface
DistributedLocker
{

RLock
lock
(
String
 lockKey);

RLock
lock
(
String
 lockKey, 
int
 timeout);

RLock
lock
(
String
 lockKey, 
TimeUnit
 unit, 
int
 timeout);

boolean
 tryLock(
String
 lockKey, 
TimeUnit
 unit, 
int
 waitTime, 
int
 leaseTime);

void
 unlock(
String
 lockKey);

void
 unlock(
RLock
lock
);
}

/**
 * @author gourd
 */
@Component
publicclass
RedisDistributedLocker
implements
DistributedLocker
{

@Autowired
private
RedissonClient
 redissonClient;

@Override
public
RLock
lock
(
String
 lockKey) {
RLock
lock
= redissonClient.getLock(lockKey);
lock
.
lock
();
returnlock
;
}

@Override
public
RLock
lock
(
String
 lockKey, 
int
 leaseTime) {
RLock
lock
= redissonClient.getLock(lockKey);
lock
.
lock
(leaseTime, 
TimeUnit
.SECONDS);
returnlock
;
}

@Override
public
RLock
lock
(
String
 lockKey, 
TimeUnit
 unit ,
int
 timeout) {
RLock
lock
= redissonClient.getLock(lockKey);
lock
.
lock
(timeout, unit);
returnlock
;
}

@Override
publicboolean
 tryLock(
String
 lockKey, 
TimeUnit
 unit, 
int
 waitTime, 
int
 leaseTime) {
RLock
lock
= redissonClient.getLock(lockKey);
try
{
returnlock
.tryLock(waitTime, leaseTime, unit);
} 
catch
(
InterruptedException
 e) {
returnfalse
;
}
}

@Override
publicvoid
 unlock(
String
 lockKey) {
RLock
lock
= redissonClient.getLock(lockKey);
lock
.unlock();
}

@Override
publicvoid
 unlock(
RLock
lock
) {
lock
.unlock();
}
}

测试

模拟并发测试

/**
 * redis分布式锁控制器
 * @author gourd
 * @since 2019-07-30
 */
@RestController
@Api
(tags = 
"redisson"
, description = 
"redis分布式锁控制器"
)
@RequestMapping
(
"/redisson"
)
@Slf4j
publicclass
RedissonLockController
{

/**
     * 锁测试共享变量
     */
private
Integer
 lockCount = 
10
;

/**
     * 无锁测试共享变量
     */
private
Integer
 count = 
10
;

/**
     * 模拟线程数
     */
privatestaticint
 threadNum = 
10
;

/**
     * 模拟并发测试加锁和不加锁
     * @return
     */
@GetMapping
(
"/test"
)
@ApiOperation
(value = 
"模拟并发测试加锁和不加锁"
)
publicvoidlock
(){
// 计数器
final
CountDownLatch
 countDownLatch = 
new
CountDownLatch
(
1
);
for
(
int
 i = 
0
; i < threadNum; i ++) {
MyRunnable
 myRunnable = 
new
MyRunnable
(countDownLatch);
Thread
 myThread = 
new
Thread
(myRunnable);
            myThread.start();
}
// 释放所有线程
        countDownLatch.countDown();
}

/**
     * 加锁测试
     */
privatevoid
 testLockCount() {
String
 lockKey = 
"lock-test"
;
try
{
// 加锁，设置超时时间2s
RedisLockUtil
.
lock
(lockKey,
2
, 
TimeUnit
.SECONDS);
            lockCount--;
            log.info(
"lockCount值："
+lockCount);
}
catch
(
Exception
 e){
            log.error(e.getMessage(),e);
}
finally
{
// 释放锁
RedisLockUtil
.unlock(lockKey);
}
}

/**
     * 无锁测试
     */
privatevoid
 testCount() {
        count--;
        log.info(
"count值："
+count);
}


publicclass
MyRunnable
implements
Runnable
{
/**
         * 计数器
         */
final
CountDownLatch
 countDownLatch;

public
MyRunnable
(
CountDownLatch
 countDownLatch) {
this
.countDownLatch = countDownLatch;
}

@Override
publicvoid
 run() {
try
{
// 阻塞当前线程，直到计时器的值为0
                countDownLatch.
await
();
} 
catch
(
InterruptedException
 e) {
                log.error(e.getMessage(),e);
}
// 无锁操作
            testCount();
// 加锁操作
            testLockCount();
}

}

}