Redis教程
redis分布式锁
本文主要是介绍redis分布式锁，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！
package lock;
//加锁设置的参数
public class LockParam {
//锁的key
private String lockKey;
//尝试获得锁的时间（单位：毫秒），默认值：3000毫秒
private Long tryLockTime;
//尝试获得锁后，持有锁的时间（单位：毫秒），默认值：5000毫秒
private Long holdLockTime;
public String getLockKey() {
return lockKey;
}
public void setLockKey(String lockKey) {
this.lockKey = lockKey;
}
public Long getTryLockTime() {
return tryLockTime;
}
public void setTryLockTime(Long tryLockTime) {
this.tryLockTime = tryLockTime;
}
public Long getHoldLockTime() {
return holdLockTime;
}
public void setHoldLockTime(Long holdLockTime) {
this.holdLockTime = holdLockTime;
}
public LockParam(String lockKey){
this(lockKey,1000*3L,1000*5L);
};
public LockParam(String lockKey,Long tryLockTime){
this(lockKey,tryLockTime,1000*5L);
};
public LockParam(String lockKey,Long tryLockTime,Long holdLockTime){
this.lockKey = lockKey;
this.tryLockTime = tryLockTime;
this.holdLockTime = holdLockTime;
};
}
//redis分布式锁实现
package lock;
import lombok.extern.slf4j.Slf4j;
import redis.clients.jedis.Jedis;
import java.util.Collections;
import java.util.UUID;
/**
* redis分布式锁
*/
@Slf4j
public class RedisLock {
//锁key的前缀
private final static String prefix_key = "redisLock:";
//释放锁的lua脚本
private final static String unLockScript = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
//执行unLockScript脚本，释放锁成功值
private final static Long unLockSuccess = 1L;
//加锁设置的参数（key值、超时时间、持有锁的时间）
private LockParam lockParam;
//尝试获得锁的截止时间【lockParam.getTryLockTime()+System.currentTimeMillis()】
private Long tryLockEndTime;
//redis加锁的key
private String redisLockKey;
//redis加锁的vlaus
private String redisLockValue;
//redis加锁的成功标示
private Boolean holdLockSuccess= Boolean.FALSE;
//jedis实例
private Jedis jedis;
//获取jedis实例
private Jedis getJedis(){
return this.jedis;
}
//关闭jedis
private void closeJedis(Jedis jedis){
jedis.close();
jedis = null;
}
public RedisLock(LockParam lockParam){
if(lockParam==null){
new RuntimeException("lockParam is null");
}
if(lockParam.getLockKey()==null || lockParam.getLockKey().trim().length()==0){
new RuntimeException("lockParam lockKey is error");
}
this.lockParam = lockParam;
this.tryLockEndTime = lockParam.getTryLockTime()+System.currentTimeMillis();
this.redisLockKey = prefix_key.concat(lockParam.getLockKey());
this.redisLockValue = UUID.randomUUID().toString().replaceAll("-","");
//todo 到时候可以更换获取Jedis实例的实现
jedis = new Jedis("127.0.0.1",6379);
}
/**
* 加锁
* @return 成功返回true，失败返回false
*/
public boolean lock() {
while(true){
//判断是否超过了，尝试获取锁的时间
if(System.currentTimeMillis()>tryLockEndTime){
return false;
}
//尝试获取锁
holdLockSuccess = tryLock();
if(Boolean.TRUE.equals(holdLockSuccess)){
return true;//获取锁成功
}
try {
//获得锁失败，休眠50毫秒再去尝试获得锁,避免一直请求redis，导致redis cpu飙升
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
/**
* 执行一次加锁操作：成功返回true 失败返回false
* @return 成功返回true，失败返回false
*/
private boolean tryLock() {
try {
String result = getJedis().set(redisLockKey,redisLockValue, "NX", "PX", lockParam.getHoldLockTime());
if ("OK".equals(result)) {
return true;
}
}catch (Exception e){
e.printStackTrace();
//log.warn("tryLock failure redisLockKey:{} redisLockValue:{} lockParam:{}",redisLockKey,redisLockValue,lockParam,e);
}
return false;
}
/**
* 解锁
* @return 成功返回true，失败返回false
*/
public Boolean unlock() {
Object result = null;
try {
//获得锁成功，才执行lua脚本
if(Boolean.TRUE.equals(holdLockSuccess)){
//执行Lua脚本
result = getJedis().eval(unLockScript, Collections.singletonList(redisLockKey), Collections.singletonList(redisLockValue));
if (unLockSuccess.equals(result)) {//释放成功
return true;
}
}
} catch (Exception e) {
e.printStackTrace();
//log.warn("unlock failure redisLockKey:{} redisLockValue:{} lockParam:{} result:{}",redisLockKey,redisLockValue,lockParam,result,e);
} finally {
this.closeJedis(jedis);
}
return false;
}
}
//测试类
package lock;
import lombok.extern.slf4j.Slf4j;
@Slf4j
public class test {
static String lockKey = "66688";
public static void main(String[] args) throws InterruptedException {
System.out.println();
System.out.println("下面测试两个线程同时，抢占锁的结果");
Thread thread1 = new Thread(()->{
testRedisLock();
});
thread1.setName("我是线程1");
Thread thread2 = new Thread(()->{
testRedisLock();
});
thread2.setName("我是线程2");
//同时启动线程
thread1.start();
thread2.start();
Thread.sleep(1000*20);
System.out.println("-----------------我是一条分割线----------------");
System.out.println("");
System.out.println("");
System.out.println("");
System.out.println("下面是测试 一个线程获取锁成功后，由于业务执行时间超过了设置持有锁的时间，是否会把其他线程持有的锁给释放掉");
Thread thread3 = new Thread(()->{
testRedisLock2();
});
thread3.setName("我是线程3");
thread3.start();
Thread.sleep(1000*1);//暂停一秒是为了让线程3获的到锁
Thread thread4 = new Thread(()->{
testRedisLock();
});
thread4.setName("我是线程4");
thread4.start();
}
public static void testRedisLock(){
LockParam lockParam = new LockParam(lockKey);
lockParam.setTryLockTime(2000L);//2秒时间尝试获得锁
lockParam.setHoldLockTime(1000*10L);//获得锁成功后持有锁10秒时间
RedisLock redisLock = new RedisLock(lockParam);
try {
Boolean lockFlag = redisLock.lock();
System.out.println("加锁结果：{}"+lockFlag);
if(lockFlag){
try {
//20秒模拟处理业务代码时间
Thread.sleep(1000*5L);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}catch (Exception e) {
System.out.println("testRedisLock e---->"+e);
}finally {
boolean unlockResp = redisLock.unlock();
System.out.println("释放锁结果:{}"+unlockResp);
}
}
public static void testRedisLock2(){
LockParam lockParam = new LockParam(lockKey);
lockParam.setTryLockTime(1000*2L);//2秒时间尝试获得锁
lockParam.setHoldLockTime(1000*2L);//获得锁成功后持有锁2秒时间
RedisLock redisLock = new RedisLock(lockParam);
try {
Boolean lockFlag = redisLock.lock();
System.out.println("加锁结果：{}"+lockFlag);
if(lockFlag){
try {
//10秒模拟处理业务代码时间
Thread.sleep(1000*10L);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}catch (Exception e) {
System.out.println("testRedisLock e---->"+e);
}finally {
boolean unlockResp = redisLock.unlock();
System.out.println("释放锁结果:{}"+unlockResp);
}
}
}
//pom.xml文件
<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>
<groupId>com.cn</groupId>
<artifactId>redisLock</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>war</packaging>
<dependencies>
<dependency>
<groupId>org.redisson</groupId>
<artifactId>redisson-spring-boot-starter</artifactId>
<version>3.11.5</version>
</dependency>
<!-- -->
<dependency>
<groupId>redis.clients</groupId>
<artifactId>jedis</artifactId>
<version>2.9.3</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>RELEASE</version>
<optional>true</optional>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>
这篇关于redis分布式锁的文章就介绍到这儿，希望我们推荐的文章对大家有所帮助，也希望大家多多支持为之网！
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