1.Redisson簡介
Redis 是最流行的 NoSQL 數據庫解決方案之一,而 Java 是世界上最流行(注意,我沒有說“最好”)的編程語言之一。雖然兩者看起來很自然地在一起“工作”,但是要知道,Redis 其實並沒有對 Java 提供原生支持。
相反,作爲 Java 開發人員,我們若想在程序中集成 Redis,必須使用 Redis 的第三方庫。而 Redisson 就是用於在 Java 程序中操作 Redis 的庫,它使得我們可以在程序中輕鬆地使用 Redis。Redisson 在 java.util 中常用接口的基礎上,爲我們提供了一系列具有分佈式特性的工具類。
Redisson底層採用的是Netty 框架。支持Redis 2.8以上版本,支持Java1.6+以上版本。
2.Redisson實現分佈式鎖的步驟
2.1.引入依賴
引入重要的兩個依賴,一個是spring-boot-starter-data-redis,一個是redisson:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
<dependency>
<groupId>org.redisson</groupId>
<artifactId>redisson</artifactId>
<version>3.7.5</version>
</dependency>
2.2.application.properties
# Redis服務器地址(默認session使用)
spring.redis.host=127.0.0.1
# Redis服務器連接密碼(默認爲空)
# spring.redis.password=
# Redis服務器連接端口
spring.redis.port=6379
2.3.定義Loker
接口編程的思想還是要保持的。我們定義一個Loker接口,用於分佈式鎖的一些操作:
package com.bruceliu.lock;
/**
* @BelongsProject: RedissonLock
* @BelongsPackage: com.bruceliu.lock
* @Author: bruceliu
* @QQ:1241488705
* @CreateTime: 2020-05-08 10:20
* @Description: 鎖接口
*/
import java.util.concurrent.TimeUnit;
public interface Locker {
/**
* 獲取鎖,如果鎖不可用,則當前線程處於休眠狀態,直到獲得鎖爲止。
*
* @param lockKey
*/
void lock(String lockKey);
/**
* 釋放鎖
*
* @param lockKey
*/
void unlock(String lockKey);
/**
* 獲取鎖,如果鎖不可用,則當前線程處於休眠狀態,直到獲得鎖爲止。如果獲取到鎖後,執行結束後解鎖或達到超時時間後會自動釋放鎖
*
* @param lockKey
* @param timeout
*/
void lock(String lockKey, int timeout);
/**
* 獲取鎖,如果鎖不可用,則當前線程處於休眠狀態,直到獲得鎖爲止。如果獲取到鎖後,執行結束後解鎖或達到超時時間後會自動釋放鎖
*
* @param lockKey
* @param unit
* @param timeout
*/
void lock(String lockKey, TimeUnit unit, int timeout);
/**
* 嘗試獲取鎖,獲取到立即返回true,未獲取到立即返回false
*
* @param lockKey
* @return
*/
boolean tryLock(String lockKey);
/**
* 嘗試獲取鎖,在等待時間內獲取到鎖則返回true,否則返回false,如果獲取到鎖,則要麼執行完後程序釋放鎖,
* 要麼在給定的超時時間leaseTime後釋放鎖
*
* @param lockKey
* @param waitTime
* @param leaseTime
* @param unit
* @return
*/
boolean tryLock(String lockKey, long waitTime, long leaseTime, TimeUnit unit)
throws InterruptedException;
/**
* 鎖是否被任意一個線程鎖持有
*
* @param lockKey
* @return
*/
boolean isLocked(String lockKey);
}
有了Locker接口,我們再添加一個基於Redisson的實現類RedissonLocker,實現Locker中的方法:
package com.bruceliu.lock;
/**
* @BelongsProject: RedissonLock
* @BelongsPackage: com.bruceliu.lock
* @Author: bruceliu
* @QQ:1241488705
* @CreateTime: 2020-05-08 10:20
* @Description: 基於Redisson的分佈式鎖
*/
import java.util.concurrent.TimeUnit;
import org.redisson.api.RLock;
import org.redisson.api.RedissonClient;
public class RedissonLocker implements Locker {
private RedissonClient redissonClient;
public RedissonLocker(RedissonClient redissonClient) {
super();
this.redissonClient = redissonClient;
}
@Override
public void lock(String lockKey) {
RLock lock = redissonClient.getLock(lockKey);
lock.lock();
}
@Override
public void unlock(String lockKey) {
RLock lock = redissonClient.getLock(lockKey);
lock.unlock();
}
@Override
public void lock(String lockKey, int leaseTime) {
RLock lock = redissonClient.getLock(lockKey);
lock.lock(leaseTime, TimeUnit.SECONDS);
}
@Override
public void lock(String lockKey, TimeUnit unit, int timeout) {
RLock lock = redissonClient.getLock(lockKey);
lock.lock(timeout, unit);
}
public void setRedissonClient(RedissonClient redissonClient) {
this.redissonClient = redissonClient;
}
@Override
public boolean tryLock(String lockKey) {
RLock lock = redissonClient.getLock(lockKey);
return lock.tryLock();
}
@Override
public boolean tryLock(String lockKey, long waitTime, long leaseTime,
TimeUnit unit) throws InterruptedException{
RLock lock = redissonClient.getLock(lockKey);
return lock.tryLock(waitTime, leaseTime, unit);
}
@Override
public boolean isLocked(String lockKey) {
RLock lock = redissonClient.getLock(lockKey);
return lock.isLocked();
}
}
2.4.定義工具類
有了Locker和實現類RedissonLocker,我們總不能一直去創建RedissonLocker對象或者不斷的在每個要使用到分佈式鎖的地方都注入RedissonLocker的對象,所以我們定義一個工具類LockUtil,到時候想哪裏使用就直接使用工具類的靜態方法就行了:
package com.bruceliu.utils;
/**
* @BelongsProject: RedissonLock
* @BelongsPackage: com.bruceliu.utils
* @Author: bruceliu
* @QQ:1241488705
* @CreateTime: 2020-05-08 10:21
* @Description: TODO
*/
import com.bruceliu.lock.Locker;
import java.util.concurrent.TimeUnit;
/**
* redis分佈式鎖工具類
*
*/
public final class LockUtil {
private static Locker locker;
/**
* 設置工具類使用的locker
* @param locker
*/
public static void setLocker(Locker locker) {
LockUtil.locker = locker;
}
/**
* 獲取鎖
* @param lockKey
*/
public static void lock(String lockKey) {
locker.lock(lockKey);
}
/**
* 釋放鎖
* @param lockKey
*/
public static void unlock(String lockKey) {
locker.unlock(lockKey);
}
/**
* 獲取鎖,超時釋放
* @param lockKey
* @param timeout
*/
public static void lock(String lockKey, int timeout) {
locker.lock(lockKey, timeout);
}
/**
* 獲取鎖,超時釋放,指定時間單位
* @param lockKey
* @param unit
* @param timeout
*/
public static void lock(String lockKey, TimeUnit unit, int timeout) {
locker.lock(lockKey, unit, timeout);
}
/**
* 嘗試獲取鎖,獲取到立即返回true,獲取失敗立即返回false
* @param lockKey
* @return
*/
public static boolean tryLock(String lockKey) {
return locker.tryLock(lockKey);
}
/**
* 嘗試獲取鎖,在給定的waitTime時間內嘗試,獲取到返回true,獲取失敗返回false,獲取到後再給定的leaseTime時間超時釋放
* @param lockKey
* @param waitTime
* @param leaseTime
* @param unit
* @return
* @throws InterruptedException
*/
public static boolean tryLock(String lockKey, long waitTime, long leaseTime,
TimeUnit unit) throws InterruptedException {
return locker.tryLock(lockKey, waitTime, leaseTime, unit);
}
/**
* 鎖釋放被任意一個線程持有
* @param lockKey
* @return
*/
public static boolean isLocked(String lockKey) {
return locker.isLocked(lockKey);
}
}
2.5.Redisson的配置類
現在我們開始配置吧,創建一個redisson的配置類RedissonConfig,內容如下:
package com.bruceliu.config;
import java.io.IOException;
import com.bruceliu.lock.RedissonLocker;
import com.bruceliu.utils.LockUtil;
import org.redisson.Redisson;
import org.redisson.api.RedissonClient;
import org.redisson.config.Config;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
/**
* @BelongsProject: RedissonLock
* @BelongsPackage: com.bruceliu.config
* @Author: bruceliu
* @QQ:1241488705
* @CreateTime: 2020-05-08 10:22
* @Description: TODO
*/
@Configuration
public class RedissonConfig {
@Value("${spring.redis.host}")
private String host;
@Value("${spring.redis.port}")
private String port;
//@Value("${spring.redis.password}")
//private String password;
/**
* RedissonClient,單機模式
* @return
* @throws IOException
*/
@Bean(destroyMethod = "shutdown")
public RedissonClient redisson() throws IOException {
Config config = new Config();
//config.useSingleServer().setAddress("redis://" + host + ":" + port).setPassword(password);
config.useSingleServer().setAddress("redis://" + host + ":" + port);
return Redisson.create(config);
}
@Bean
public RedissonLocker redissonLocker(RedissonClient redissonClient){
RedissonLocker locker = new RedissonLocker(redissonClient);
//設置LockUtil的鎖處理對象
LockUtil.setLocker(locker);
return locker;
}
}
2.6.Redisson分佈式鎖業務類
package com.bruceliu.service;
import com.bruceliu.utils.LockUtil;
import java.util.concurrent.TimeUnit;
/**
* @BelongsProject: RedissonLock
* @BelongsPackage: com.bruceliu.service
* @Author: bruceliu
* @QQ:1241488705
* @CreateTime: 2020-05-08 10:26
* @Description: TODO
*/
public class SkillService {
int n = 500;
public void seckill() {
//加鎖
LockUtil.lock("resource", TimeUnit.SECONDS,5000);
try {
System.out.println(Thread.currentThread().getName() + "獲得了鎖");
Thread.sleep(3000);
System.out.println(--n);
} catch (Exception e) {
//異常處理
}finally{
//釋放鎖
LockUtil.unlock("resource");
System.out.println(Thread.currentThread().getName() + "釋放了鎖");
}
}
}
2.7.Redisson分佈式鎖測試
package com.bruceliu.test;
import com.bruceliu.App;
import com.bruceliu.service.SkillService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
/**
* @BelongsProject: RedissonLock
* @BelongsPackage: com.bruceliu.test
* @Author: bruceliu
* @QQ:1241488705
* @CreateTime: 2020-05-08 10:29
* @Description: TODO
*/
@RunWith(SpringRunner.class)
@SpringBootTest(classes = App.class)
public class TestLock {
@Test
public void testLock() throws Exception{
SkillService service = new SkillService();
for (int i = 0; i < 10; i++) {
ThreadA threadA = new ThreadA(service);
threadA.setName("ThreadNameA->"+i);
threadA.start();
}
Thread.sleep(50000);
}
}
class ThreadA extends Thread {
private SkillService skillService;
public ThreadA(SkillService skillService) {
this.skillService = skillService;
}
@Override
public void run() {
skillService.seckill();
}
}
運行結果:
註釋文中加鎖代碼:
public void seckill() {
//加鎖
//LockUtil.lock("resource", TimeUnit.SECONDS,5000);
try {
System.out.println(Thread.currentThread().getName() + "獲得了鎖");
Thread.sleep(3000);
System.out.println(--n);
} catch (Exception e) {
//異常處理
}finally{
//釋放鎖
//LockUtil.unlock("resource");
System.out.println(Thread.currentThread().getName() + "釋放了鎖");
}
}
運行結果:
可以看到存在併發的問題!