feat(cache): 添加店铺服务的 Redis 缓存功能

- 新增 RedisIdWorker 工具类，用于生成分布式 ID
- 在 ShopServiceImpl 中基于互斥锁解决缓存击穿问题
- 添加测试用例验证 ID 生成和缓存功能

src/main/java/com/hmdp/service/impl/ShopServiceImpl.java

@@ -1,5 +1,7 @@
 package com.hmdp.service.impl;
 
+import cn.hutool.core.bean.BeanUtil;
+import cn.hutool.core.util.BooleanUtil;
 import cn.hutool.core.util.StrUtil;
 import cn.hutool.json.JSONUtil;
 import com.hmdp.dto.Result;
@@ -32,6 +34,14 @@ public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IS
     private StringRedisTemplate stringRedisTemplate;
     @Override
     public Result queryById(Long id) {
+        Shop shop = queryByIdWithMutex(id);
+        if (shop == null){
+            return Result.fail("店铺不存在");
+        }
+        return Result.ok(shop);
+    }
+
+    public Shop queryByIdWithRedis(Long id) {
         // 使用redis缓存
         // 查询缓存
         String cacheShop = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
@@ -40,16 +50,73 @@ public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IS
         if(StrUtil.isNotBlank(cacheShop)){
             // 存在直接返回
             shop = JSONUtil.toBean(cacheShop, Shop.class);
-            return Result.ok(shop);
+            return shop;
         }
         // 不存在，查询数据库
         shop = getById(id);
         if(shop == null){
             // 数据库不存在，返回错误
-            return Result.fail("店铺不存在");
+            return null;
+            // 解决缓存穿透的话，就在这往redis存一个null
         }
         stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
-        return Result.ok(shop);
+        return shop;
+    }
+
+    public Shop queryByIdWithMutex(Long id) {
+        String key = CACHE_SHOP_KEY + id;
+        // 使用redis缓存
+        // 查询缓存
+        String cacheShop = stringRedisTemplate.opsForValue().get(key);
+        // 判断是否存在
+        Shop shop = new Shop();
+        if(StrUtil.isNotBlank(cacheShop)){
+            // 存在直接返回
+            shop = JSONUtil.toBean(cacheShop, Shop.class);
+            return shop;
+        }
+
+        boolean isLock =  false;
+        try {
+            isLock =tryLock(id);
+            // 不存在，尝试获取互斥锁
+            if(isLock){
+                // 获取到互斥锁，查询数据库
+                shop = getById(id);
+                Thread.sleep(200); //模拟重建时的延迟
+                if(shop == null){
+                    // 解决缓存穿透的话，就在这往redis存一个null
+                    stringRedisTemplate.opsForValue().set(key, "",CACHE_SHOP_TTL, TimeUnit.MINUTES);
+                    // 数据库不存在，返回错误
+                    return null;
+                }
+                // 存入缓存
+                stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
+            }
+            // 没有获取到互斥锁
+            // 休眠后重新执行
+            Thread.sleep(50);
+            return queryByIdWithMutex (id);
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        } finally {
+            // 释放互斥锁
+            if (isLock) {
+                delectLock(id);
+            }
+            
+        }
+    }
+
+    private boolean tryLock(Long id) {
+        // 本质就是设置一个redis缓存，key任意
+        // 设置10秒过期时间防止死锁，10秒就够，因为这些请求一半都很快
+        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent("lock:shop:"+id, "1",10, TimeUnit.SECONDS);
+        return BooleanUtil.isTrue(flag);
+    }
+    private void delectLock(Long id) {
+        // 本质就是删除上面key对应的缓存
+        stringRedisTemplate.delete("lock:shop:"+id);
     }
 
     @Override

src/main/java/com/hmdp/utils/RedisIdWorker.java

@@ -0,0 +1,31 @@
+package com.hmdp.utils;
+
+import org.springframework.data.redis.core.StringRedisTemplate;
+import org.springframework.stereotype.Component;
+
+import javax.annotation.Resource;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.time.format.DateTimeFormatter;
+
+@Component
+public class RedisIdWorker {
+    private static final long BEGIN_TIMESTAMP = 1640995200L;
+    private static final long COUNT_BITS = 32;
+    @Resource
+    private StringRedisTemplate stringRedisTemplate;
+    // 拼接一个时间戳，再加一个根据输入的字符串自增长的32位id
+    public long nextId(String prefix) {
+        LocalDateTime now = LocalDateTime.now();
+        long GapSecond = now.toEpochSecond(ZoneOffset.UTC)-BEGIN_TIMESTAMP;
+        String date = now.format(DateTimeFormatter.ofPattern("yyyyMMdd"));
+        long count = stringRedisTemplate.opsForValue().increment("icr:" + prefix+date);
+        return GapSecond <<32 | count;
+    }
+
+
+//    public static void main(String[] args) {
+//        LocalDateTime localDateTime = LocalDateTime.of(2022, 1, 1, 0, 0, 0);
+//        System.out.println(localDateTime.toEpochSecond(ZoneOffset.UTC)); //获取这个时间的秒数
+//    }
+}

src/test/java/com/hmdp/HmDianPingApplicationTests.java

@@ -1,9 +1,27 @@
 package com.hmdp;
 
+import com.hmdp.utils.RedisIdWorker;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
-@SpringBootTest
+import javax.annotation.Resource;
-class HmDianPingApplicationTests {
 
 
+@SpringBootTest()
+@RunWith(SpringJUnit4ClassRunner.class)
+public class HmDianPingApplicationTests {
+    @Autowired
+    RedisIdWorker redisIdWorker;
+
+    @Test
+    public void testIdWorker() {
+        for (int i = 0; i < 100; i++) {
+            long id = redisIdWorker.nextId("order");
+            System.out.println("id = " + id);
+        }
+    }
+
 }