7.22 数据缓存与缓存降级

group-buying-sys-app/src/main/java/edu/whut/config/DCCValueBeanFactory.java

@@ -53,7 +53,7 @@ public class DCCValueBeanFactory implements BeanPostProcessor {
      */
     @Bean("dccTopic")
     public RTopic dccRedisTopicListener(RedissonClient redissonClient) {
-        RTopic topic = redissonClient.getTopic("group_buy_market_dcc");
+        RTopic topic = redissonClient.getTopic("group_buy_market_dcc"); //只要有任何客户端往 group_buy_market_dcc 发布消息，这个监听回调就会被触发
 
         topic.addListener(String.class, (channel, message) -> {
             // message 示例： "cutRange:30"

group-buying-sys-app/src/test/java/edu/whut/test/ApiTest.java

@@ -10,6 +10,7 @@ import org.springframework.test.context.junit4.SpringRunner;
 
 import javax.annotation.Resource;
 import java.util.concurrent.CountDownLatch;
+import java.util.function.Supplier;
 
 @Slf4j
 @RunWith(SpringRunner.class)
@@ -36,5 +37,25 @@ public class ApiTest {
         countDownLatch.await();
     }
 
+    @Test
+    public void test_Supplier(){
+        // 创建一个 Supplier 实例，返回一个字符串
+        Supplier<String> stringSupplier = () -> "Hello, smile!";
+
+        // 使用 get() 方法获取 Supplier 提供的值
+        String result = stringSupplier.get();
+
+        // 输出结果
+        System.out.println(result);
+
+        // 另一个示例，使用 Supplier 提供当前时间
+        Supplier<Long> currentTimeSupplier = System::currentTimeMillis;
+
+        // 获取当前时间
+        Long currentTime = currentTimeSupplier.get();
+
+        // 输出当前时间
+        System.out.println("Current time in milliseconds: " + currentTime);
+    }
 
 }

group-buying-sys-infrastructure/src/main/java/edu/whut/infrastructure/adapter/repository/AbstractRepository.java

@@ -0,0 +1,92 @@
+package edu.whut.infrastructure.adapter.repository;
+import edu.whut.infrastructure.dcc.DCCService;
+import edu.whut.infrastructure.redis.IRedisService;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.annotation.Resource;
+import java.util.function.Supplier;
+
+/**
+ * 仓储抽象类
+ */
+public abstract class AbstractRepository {
+
+    private final Logger logger = LoggerFactory.getLogger(AbstractRepository.class);
+
+    @Resource
+    protected IRedisService redisService;
+
+    @Resource
+    protected DCCService dccService;
+
+    /**
+     * 通用缓存处理方法
+     * 优先从缓存获取，缓存不存在则从数据库获取并写入缓存
+     *
+     * @param cacheKey      缓存键
+     * @param dbFallback    数据库查询函数
+     * @param <T>           返回类型
+     * @return              查询结果
+     */
+    protected <T> T getFromCacheOrDb(String cacheKey, Supplier<T> dbFallback) {
+        // 判断是否开启缓存
+        if (dccService.isCacheOpenSwitch()) {
+            // 从缓存获取
+            T cacheResult = redisService.getValue(cacheKey);
+            // 缓存存在则直接返回
+            if (null != cacheResult) {
+                return cacheResult;
+            }
+            // 缓存不存在则从数据库获取
+            T dbResult = dbFallback.get();
+            // 数据库查询结果为空则直接返回
+            if (null == dbResult) {
+                return null;
+            }
+            // 写入缓存
+            redisService.setValue(cacheKey, dbResult);
+            return dbResult;
+        } else {
+            // 缓存未开启，直接从数据库获取
+            logger.warn("缓存降级 {}", cacheKey);
+            return dbFallback.get();
+        }
+    }
+
+    /**
+     * 通用缓存处理方法（带过期时间）
+     * 优先从缓存获取，缓存不存在则从数据库获取并写入缓存
+     *
+     * @param cacheKey      缓存键
+     * @param dbFallback    数据库查询函数
+     * @param expired       过期时间
+     * @param <T>           返回类型
+     * @return              查询结果
+     */
+    protected <T> T getFromCacheOrDb(String cacheKey, Supplier<T> dbFallback, long expired) {
+        // 判断是否开启缓存
+        if (dccService.isCacheOpenSwitch()) {
+            // 从缓存获取
+            T cacheResult = redisService.getValue(cacheKey);
+            // 缓存存在则直接返回
+            if (null != cacheResult) {
+                return cacheResult;
+            }
+            // 缓存不存在则从数据库获取
+            T dbResult = dbFallback.get();
+            // 数据库查询结果为空则直接返回
+            if (null == dbResult) {
+                return null;
+            }
+            // 写入缓存（带过期时间）
+            redisService.setValue(cacheKey, dbResult, expired);
+            return dbResult;
+        } else {
+            // 缓存未开启，直接从数据库获取
+            logger.warn("缓存降级 {}", cacheKey);
+            return dbFallback.get();
+        }
+    }
+
+}

group-buying-sys-infrastructure/src/main/java/edu/whut/infrastructure/adapter/repository/ActivityRepository.java

@@ -25,7 +25,7 @@ import java.util.stream.Collectors;
 @Repository
 @RequiredArgsConstructor
 @Slf4j
-public class ActivityRepository implements IActivityRepository {
+public class ActivityRepository extends AbstractRepository implements IActivityRepository {
 
     private final IGroupBuyActivityDao groupBuyActivityDao;
 
@@ -45,12 +45,17 @@ public class ActivityRepository implements IActivityRepository {
 
     @Override
     public GroupBuyActivityDiscountVO queryGroupBuyActivityDiscountVO(Long activityId) {
-        GroupBuyActivity groupBuyActivityRes = groupBuyActivityDao.queryValidGroupBuyActivityId(activityId);
+        // 优先从缓存获取&写缓存，注意如果实现了后台配置，在更新时要更库，删缓存。
+        // TODO:数据更新时更库，删缓存还未实现
+        GroupBuyActivity groupBuyActivityRes = getFromCacheOrDb(GroupBuyActivity.cacheRedisKey(activityId),
+                () -> groupBuyActivityDao.queryValidGroupBuyActivityId(activityId));
         if (null == groupBuyActivityRes) return null;
 
         String discountId = groupBuyActivityRes.getDiscountId();
 
-        GroupBuyDiscount groupBuyDiscountRes = groupBuyDiscountDao.queryGroupBuyActivityDiscountByDiscountId(discountId);
+        // 优先从缓存获取&写缓存
+        GroupBuyDiscount groupBuyDiscountRes = getFromCacheOrDb(GroupBuyDiscount.cacheRedisKey(discountId),
+                () -> groupBuyDiscountDao.queryGroupBuyActivityDiscountByDiscountId(discountId));
         if (null == groupBuyDiscountRes) return null;
 
         GroupBuyActivityDiscountVO.GroupBuyDiscount groupBuyDiscount = GroupBuyActivityDiscountVO.GroupBuyDiscount.builder()

group-buying-sys-infrastructure/src/main/java/edu/whut/infrastructure/dao/po/GroupBuyActivity.java

@@ -46,5 +46,8 @@ public class GroupBuyActivity {
     private Date createTime;
     /** 更新时间 */
     private Date updateTime;
+    public static String cacheRedisKey(Long activityId) {
+        return "group_buy_market_edu.whut.infrastructure.dao.po.GroupBuyActivity_" + activityId;
+    }
 
 }

group-buying-sys-infrastructure/src/main/java/edu/whut/infrastructure/dao/po/GroupBuyDiscount.java

@@ -24,7 +24,7 @@ public class GroupBuyDiscount {
     /**
      * 折扣ID
      */
-    private Integer discountId;
+    private String discountId;
 
     /**
      * 折扣标题
@@ -66,4 +66,8 @@ public class GroupBuyDiscount {
      */
     private Date updateTime;
 
+    public static String cacheRedisKey(String discountId) {
+        return "group_buy_market_edu.whut.infrastructure.dao.po.GroupBuyDiscount_" + discountId;
+    }
+
 }

group-buying-sys-infrastructure/src/main/java/edu/whut/infrastructure/dcc/DCCService.java

@@ -32,6 +32,9 @@ public class DCCService {
     @DCCValue("scBlacklist:s02c02,s03c03")
     private String scBlacklist;
 
+    @DCCValue("cacheSwitch:1")
+    private String cacheOpenSwitch;
+
     /**
      * 判断是否降级
      * @return
@@ -63,4 +66,11 @@ public class DCCService {
         return list.contains(source + channel);
     }
 
+    /**
+     * 缓存开启开关，true为开启，0为关闭
+     */
+    public boolean isCacheOpenSwitch(){
+        return "1".equals(cacheOpenSwitch);
+    }
+
 }