网站建设域名怎么收费的,二次开发公司,企业在线设计网站,广东茶叶网站建设实战篇9
设立一个在jvm外的锁监视器#xff0c;可以处理多线程的问题 实战篇10 获取锁的时候#xff0c;要同时发生获取锁以及设置到期时间。 实战篇11
thinking#xff1a;JAVA中的自动拆箱与装箱#xff1f; 【Java基础】自动拆装箱_Elephant_King的博客-CSDN博客 TR… 实战篇9
设立一个在jvm外的锁监视器可以处理多线程的问题 实战篇10 获取锁的时候要同时发生获取锁以及设置到期时间。 实战篇11
thinkingJAVA中的自动拆箱与装箱 【Java基础】自动拆装箱_Elephant_King的博客-CSDN博客 TRUE.equals():保证不会有空指针异常。
package com.hmdp.utils;public interface ILock {/*** 尝试获取锁* param timeoutSec 锁持有的超时时间过期后自动释放* return true代表获取锁成功false代表获取锁失败*/boolean tryLock(long timeoutSec);/*** 释放锁*/void unlock();
}
package com.hmdp.utils;
import org.springframework.data.redis.core.StringRedisTemplate;
import java.util.concurrent.TimeUnit;
public class SimpleRedisLock implements ILock {private String name;private StringRedisTemplate stringRedisTemplate;private static final String KEY_PREFIX lock:;public SimpleRedisLock(String name, StringRedisTemplate stringRedisTemplate) {this.name name;this.stringRedisTemplate stringRedisTemplate;}Overridepublic boolean tryLock(long timeoutSec) {//获取线程标示long threadId Thread.currentThread().getId();//释放锁Boolean success stringRedisTemplate.opsForValue().setIfAbsent(KEY_PREFIX name, threadId , timeoutSec, TimeUnit.SECONDS);return Boolean.TRUE.equals(success);}Overridepublic void unlock() {//释放锁stringRedisTemplate.delete(KEY_PREFIX name);}
}
package com.hmdp.service.impl;import com.hmdp.dto.Result;
import com.hmdp.entity.SeckillVoucher;
import com.hmdp.entity.User;
import com.hmdp.entity.Voucher;
import com.hmdp.entity.VoucherOrder;
import com.hmdp.mapper.VoucherOrderMapper;
import com.hmdp.service.ISeckillVoucherService;
import com.hmdp.service.IVoucherOrderService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisIdWorker;
import com.hmdp.utils.SimpleRedisLock;
import com.hmdp.utils.UserHolder;
import org.springframework.aop.framework.AopContext;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;import javax.annotation.Resource;
import java.time.LocalDateTime;/*** p* 服务实现类* /p** author 虎哥* since 2021-12-22*/
Service
public class VoucherOrderServiceImpl extends ServiceImplVoucherOrderMapper, VoucherOrder implements IVoucherOrderService {Resourceprivate ISeckillVoucherService seckillVoucherService;Resourceprivate RedisIdWorker redisIdWorker;Resourceprivate StringRedisTemplate stringRedisTemplate;Overridepublic Result seckillVoucher(Long voucherId) {//1查询优惠券SeckillVoucher voucher seckillVoucherService.getById(voucherId);//2判断秒杀是否开始if (voucher.getBeginTime().isAfter(LocalDateTime.now())) {//尚未开始return Result.fail(秒杀尚未开始);}//3判断秒杀是否已经结束if (voucher.getBeginTime().isBefore(LocalDateTime.now())) {//已经结束return Result.fail(秒杀已经结束);}//4判断库存是否充足if (voucher.getStock() 1) {//库存不足return Result.fail(库存不足);}//一人一锁提高效率//intern 保证指定的userId对应指定的锁//先获取锁再完成以下方法先完成方法再释放锁才能确保线程安全Long userId UserHolder.getUser().getId();//synchronized(userId.toString().intern()){//获取代理对象事务//创建锁对象SimpleRedisLock lock new SimpleRedisLock(order userId, stringRedisTemplate);//获取锁boolean isLock lock.tryLock(1200);//判断是否获取锁成功if(!isLock){//获取锁失败返回错误或重试return Result.fail(不允许重复下单);}try {//获取代理对象事务IVoucherOrderService proxy (IVoucherOrderService) AopContext.currentProxy();return proxy.createVoucherOrder(voucherId);} finally {//释放锁lock.unlock();}// }}//加上事务因为这里有两张表Transactionalpublic Result createVoucherOrder(Long voucherId) {//5一人一单Long userId UserHolder.getUser().getId();//5.1 查询订单int count query().eq(user_id, userId).eq(voucher_id, voucherId).count();//5.2 判断是否存在if (count 0) {// 用户已经购买过了return Result.fail(用户已经购买过一次);}//6扣减库存boolean success seckillVoucherService.update().setSql(stock stock - 1).eq(voucher_id, voucherId).gt(stock, 0).update();if (!success) {//扣除失败return Result.fail(库存不足);}//7创建订单VoucherOrder voucherOrder new VoucherOrder();//7.1 订单idlong orderId redisIdWorker.nextId(order);voucherOrder.setId(orderId);//7.2 用户idvoucherOrder.setUserId(userId);//7.3 优惠券idvoucherOrder.setVoucherId(voucherId);save(voucherOrder);//8返回订单idreturn Result.ok(orderId);}}
thinking我怎么知道什么时候要处理异常 最全最详细的Java异常处理机制_两个系统对接 另一个系统有异常_我是波哩个波的博客-CSDN博客 实战篇12 设置锁的标识避免误删别人的锁以达到避免多线程并发的情况发生 实战篇13 thinkinghutool的UUID 【工具类用法】Hutool里的生成唯一Id唯的工具类_hutool生成uuid-CSDN博客 thinkingjava中long和string互转 java中long和string互转_long转换string-CSDN博客 package com.hmdp.utils;
import cn.hutool.core.lang.UUID;
import org.springframework.data.redis.core.StringRedisTemplate;
import java.util.concurrent.TimeUnit;
public class SimpleRedisLock implements ILock {private String name;private StringRedisTemplate stringRedisTemplate;private static final String KEY_PREFIX lock:;private static final String ID_PREFIX UUID.randomUUID().toString(true)-;public SimpleRedisLock(String name, StringRedisTemplate stringRedisTemplate) {this.name name;this.stringRedisTemplate stringRedisTemplate;}Overridepublic boolean tryLock(long timeoutSec) {//获取线程标示String threadId ID_PREFIX Thread.currentThread().getId();//释放锁Boolean success stringRedisTemplate.opsForValue().setIfAbsent(KEY_PREFIX name, threadId, timeoutSec, TimeUnit.SECONDS);return Boolean.TRUE.equals(success);}Overridepublic void unlock() {//获取线程标示String threadId ID_PREFIX Thread.currentThread().getId();//获取锁中的标示String id stringRedisTemplate.opsForValue().get(KEY_PREFIX name);//判断标示是否一致if(threadId.equals(id)){//释放锁stringRedisTemplate.delete(KEY_PREFIX name);}}
}
实战篇14
如果仅仅用id 两个不同的jvm就会出现两个相同的id 也有可能出现bug。因此要将这块原子性因为当线程一因为回收垃圾产生阻塞情况而锁因为超时而释放时线程二就有机会趁机而入从而获取锁从而发生多线程并发的情况 实战篇15
lua的使用手册 Lua 教程 | 菜鸟教程 实战篇16 thinking没有lua标志 解决方案下载其中一个就好不要两个都下载两个插件效果是一样的。两个都下载会导致idea卡死的哦。 LUA
--比较线程标示与锁中的标示是否一致
if(redis.call(get,KEYS[1]) ARGV[1])then--释放锁 del keyreturn redis.call(del,KEYS[1])
end
return 0JAVA
package com.hmdp.utils;
import cn.hutool.core.lang.UUID;
import org.apache.ibatis.javassist.ClassPath;
import org.springframework.core.io.ClassPathResource;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;import java.util.Collection;
import java.util.Collections;
import java.util.concurrent.TimeUnit;
public class SimpleRedisLock implements ILock {private String name;private StringRedisTemplate stringRedisTemplate;private static final String KEY_PREFIX lock:;private static final String ID_PREFIX UUID.randomUUID().toString(true)-;//提前读好这个文件避免多次读取private static final DefaultRedisScriptLong UNLOCK_SCRIPT;//因为是静态的因此在静态代码块里面搞static {UNLOCK_SCRIPT new DefaultRedisScript();UNLOCK_SCRIPT.setLocation(new ClassPathResource(unlock.lua));UNLOCK_SCRIPT.setResultType(Long.class);}public SimpleRedisLock(String name, StringRedisTemplate stringRedisTemplate) {this.name name;this.stringRedisTemplate stringRedisTemplate;}Overridepublic boolean tryLock(long timeoutSec) {//获取线程标示String threadId ID_PREFIX Thread.currentThread().getId();//释放锁Boolean success stringRedisTemplate.opsForValue().setIfAbsent(KEY_PREFIX name, threadId, timeoutSec, TimeUnit.SECONDS);return Boolean.TRUE.equals(success);}Overridepublic void unlock() {//调用lua脚本stringRedisTemplate.execute(UNLOCK_SCRIPT, Collections.singletonList(KEY_PREFIXname),ID_PREFIX Thread.currentThread().getId());}
// Override
// public void unlock() {
// //获取线程标示
// String threadId ID_PREFIX Thread.currentThread().getId();
// //获取锁中的标示
// String id stringRedisTemplate.opsForValue().get(KEY_PREFIX name);
// //判断标示是否一致
// if(threadId.equals(id)){
// //释放锁
// stringRedisTemplate.delete(KEY_PREFIX name);
// }} 实战篇17 这个网站不知道为什么打不开。。
实战篇18 dependencygroupIdorg.redisson/groupIdartifactIdredisson/artifactIdversion3.13.6/version/dependency
package com.hmdp.config;import org.redisson.Redisson;
import org.redisson.api.RedissonClient;
import org.redisson.config.Config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;Configuration
public class RedissonConfig {Beanpublic RedissonClient redissonClient(){//配置Config config new Config();config.useSingleServer().setAddress(redis://localhost:6379);//创建RedissonClient对象return Redisson.create(config);}
}
package com.hmdp.service.impl;import com.hmdp.dto.Result;
import com.hmdp.entity.SeckillVoucher;
import com.hmdp.entity.User;
import com.hmdp.entity.Voucher;
import com.hmdp.entity.VoucherOrder;
import com.hmdp.mapper.VoucherOrderMapper;
import com.hmdp.service.ISeckillVoucherService;
import com.hmdp.service.IVoucherOrderService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisIdWorker;
import com.hmdp.utils.SimpleRedisLock;
import com.hmdp.utils.UserHolder;
import org.redisson.api.RLock;
import org.redisson.api.RedissonClient;
import org.springframework.aop.framework.AopContext;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;import javax.annotation.Resource;
import java.time.LocalDateTime;/*** p* 服务实现类* /p** author 虎哥* since 2021-12-22*/
Service
public class VoucherOrderServiceImpl extends ServiceImplVoucherOrderMapper, VoucherOrder implements IVoucherOrderService {Resourceprivate ISeckillVoucherService seckillVoucherService;Resourceprivate RedisIdWorker redisIdWorker;Resourceprivate StringRedisTemplate stringRedisTemplate;Resourceprivate RedissonClient redissonClient;Overridepublic Result seckillVoucher(Long voucherId) {//1查询优惠券SeckillVoucher voucher seckillVoucherService.getById(voucherId);//2判断秒杀是否开始if (voucher.getBeginTime().isAfter(LocalDateTime.now())) {//尚未开始return Result.fail(秒杀尚未开始);}//3判断秒杀是否已经结束if (voucher.getBeginTime().isBefore(LocalDateTime.now())) {//已经结束return Result.fail(秒杀已经结束);}//4判断库存是否充足if (voucher.getStock() 1) {//库存不足return Result.fail(库存不足);}//一人一锁提高效率//intern 保证指定的userId对应指定的锁//先获取锁再完成以下方法先完成方法再释放锁才能确保线程安全Long userId UserHolder.getUser().getId();//synchronized(userId.toString().intern()){//获取代理对象事务//创建锁对象// SimpleRedisLock lock new SimpleRedisLock(order: userId, stringRedisTemplate);RLock lock redissonClient.getLock(lock:order: userId);//获取锁//不传参数代表我失败了立即返回boolean isLock lock.tryLock();//判断是否获取锁成功if(!isLock){//获取锁失败返回错误或重试return Result.fail(不允许重复下单);}try {//获取代理对象事务IVoucherOrderService proxy (IVoucherOrderService) AopContext.currentProxy();return proxy.createVoucherOrder(voucherId);} finally {//释放锁lock.unlock();}// }}//加上事务因为这里有两张表Transactionalpublic Result createVoucherOrder(Long voucherId) {//5一人一单Long userId UserHolder.getUser().getId();//5.1 查询订单int count query().eq(user_id, userId).eq(voucher_id, voucherId).count();//5.2 判断是否存在if (count 0) {// 用户已经购买过了return Result.fail(用户已经购买过一次);}//6扣减库存boolean success seckillVoucherService.update().setSql(stock stock - 1).eq(voucher_id, voucherId).gt(stock, 0).update();if (!success) {//扣除失败return Result.fail(库存不足);}//7创建订单VoucherOrder voucherOrder new VoucherOrder();//7.1 订单idlong orderId redisIdWorker.nextId(order);voucherOrder.setId(orderId);//7.2 用户idvoucherOrder.setUserId(userId);//7.3 优惠券idvoucherOrder.setVoucherId(voucherId);save(voucherOrder);//8返回订单idreturn Result.ok(orderId);}}
实战篇20 实战篇21
