目录1. 方法要求1.1 方法一1.2 方法二1.3 方法三1.4 方法四2. 完整工具类代码将 StringRedisTemplate 封装成一个缓存工具类,方便以后重复使用。 1. 方法要求 在这个工具类中我们完成四
将 StringRedisTemplate 封装成一个缓存工具类,方便以后重复使用。
在这个工具类中我们完成四个方法:
我们新建一个类,先把大致框架写出来,方法的参数可以边写边完善,但是我的方法参数已经完善好了:
@Component
public class CacheClient {
private final StringRedisTemplate stringRedisTemplate;
public CacheClient(StringRedisTemplate stringRedisTemplate) {
this.stringRedisTemplate = stringRedisTemplate;
}
//方法一
public void set(String key, Object value, Long time, TimeUnit unit) {
}
//方法二
public void setWithLogicExpire(String key, Object value, Long time, TimeUnit unit) {
}
//方法三
public <R, ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type,
Long time, TimeUnit unit, Function<ID, R> dbFallback) {
}
//方法四
public <R, ID> R queryWithLogicalExpire(String prefix, ID id, String lockPre, Class<R> type,
Long time, TimeUnit unit, Function<ID, R> dbFallback) {
}
//线程池
private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
//获取锁
private boolean tryLock(String key) {
Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", LOCK_SHOP_TTL, TimeUnit.SECONDS);
return BooleanUtil.isTrue(flag);
}
//释放锁
private void unLock(String key) {
stringRedisTemplate.delete(key);
}
}
接下来我们可以不断完善这些方法。
public void set(String key, Object value, Long time, TimeUnit unit) {
stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
}
public void setWithLogicExpire(String key, Object value, Long time, TimeUnit unit) {
RedisData redisData = new RedisData();
redisData.setData(value);
redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
}
public <R, ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type,
Long time, TimeUnit unit, Function<ID, R> dbFallback) {
String key = keyPrefix + id;
//1.从redis中查询商铺缓存
String json = stringRedisTemplate.opsForValue().get(key);
//2.判断是否存在
if (StrUtil.isNotBlank(json)) {
//2.1.存在
return JSONUtil.toBean(json, type);
}
//2.2.不存在
//判断是否为空值
if (json != null) {
//不为null,则必为空
return null;
}
//3.查询数据库
R r = dbFallback.apply(id);
if (r == null) {
//3.1.不存在,缓存空值
stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
} else {
//3.2.存在,缓存数据
this.set(key, r, time, unit);
}
return r;
}
方法三用到了函数式编程,这里非常巧妙,顺便再贴一下调用方法是怎样调用的:
Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY,id,Shop.class,CACHE_SHOP_TTL,TimeUnit.MINUTES,this::getById);
public <R, ID> R queryWithLogicalExpire(String prefix, ID id, String lockPre, Class<R> type,
Long time, TimeUnit unit, Function<ID, R> dbFallback) {
//1.从redis查询商铺缓存
String key = prefix + id;
String json = stringRedisTemplate.opsForValue().get(key);
//2.判断是否存在
if (StrUtil.isBlank(json)) {
//未命中,直接返回空
return null;
}
//3.命中,判断是否过期
RedisData redisData = JSONUtil.toBean(json, RedisData.class);
R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
if (redisData.getExpireTime().isAfter(LocalDateTime.now())) {
//3.1未过期,直接返回店铺信息
return r;
}
//3.2.已过期,缓存重建
//3.3.获取锁
String lockKey = lockPre + id;
boolean flag = tryLock(lockKey);
if (flag) {
//3.4.获取成功
//4再次检查redis缓存是否过期,做double check
json = stringRedisTemplate.opsForValue().get(key);
//4.1.判断是否存在
if (StrUtil.isBlank(json)) {
//未命中,直接返回空
return null;
}
//4.2.命中,判断是否过期
redisData = JSONUtil.toBean(json, RedisData.class);
r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
if (redisData.getExpireTime().isAfter(LocalDateTime.now())) {
//4.3.未过期,直接返回店铺信息
return r;
}
//4.4过期,返回旧数据
CACHE_REBUILD_EXECUTOR.submit(() -> {
//5.重建缓存
try {
R r1 = dbFallback.apply(id);
this.setWithLogicExpire(key, r1, time, unit);
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
//释放锁
unLock(lockKey);
}
});
}
//7.获取失败,返回旧数据
return r;
}
@Component
@Slf4j
public class CacheClient {
private final StringRedisTemplate stringRedisTemplate;
public CacheClient(StringRedisTemplate stringRedisTemplate) {
this.stringRedisTemplate = stringRedisTemplate;
}
public void set(String key, Object value, Long time, TimeUnit unit) {
stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
}
public void setWithLogicExpire(String key, Object value, Long time, TimeUnit unit) {
RedisData redisData = new RedisData();
redisData.setData(value);
redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
}
public <R, ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type,
Long time, TimeUnit unit, Function<ID, R> dbFallback) {
String key = keyPrefix + id;
//1.从redis中查询商铺缓存
String json = stringRedisTemplate.opsForValue().get(key);
//2.判断是否存在
if (StrUtil.isNotBlank(json)) {
//2.1.存在
return JSONUtil.toBean(json, type);
}
//2.2.不存在
//判断是否为空值
if (json != null) {
//不为null,则必为空
return null;
}
//3.查询数据库
R r = dbFallback.apply(id);
if (r == null) {
//3.1.不存在,缓存空值
stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
} else {
//3.2.存在,缓存数据
this.set(key, r, time, unit);
}
return r;
}
public <R, ID> R queryWithLogicalExpire(String prefix, ID id, String lockPre, Class<R> type,
Long time, TimeUnit unit, Function<ID, R> dbFallback) {
//1.从redis查询商铺缓存
String key = prefix + id;
String json = stringRedisTemplate.opsForValue().get(key);
//2.判断是否存在
if (StrUtil.isBlank(json)) {
//未命中,直接返回空
return null;
}
//3.命中,判断是否过期
RedisData redisData = JSONUtil.toBean(json, RedisData.class);
R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
if (redisData.getExpireTime().isAfter(LocalDateTime.now())) {
//3.1未过期,直接返回店铺信息
return r;
}
//3.2.已过期,缓存重建
//3.3.获取锁
String lockKey = lockPre + id;
boolean flag = tryLock(lockKey);
if (flag) {
//3.4.获取成功
//4再次检查redis缓存是否过期,做double check
json = stringRedisTemplate.opsForValue().get(key);
//4.1.判断是否存在
if (StrUtil.isBlank(json)) {
//未命中,直接返回空
return null;
}
//4.2.命中,判断是否过期
redisData = JSONUtil.toBean(json, RedisData.class);
r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
if (redisData.getExpireTime().isAfter(LocalDateTime.now())) {
//4.3.未过期,直接返回店铺信息
return r;
}
//4.4过期,返回旧数据
CACHE_REBUILD_EXECUTOR.submit(() -> {
//5.重建缓存
try {
R r1 = dbFallback.apply(id);
this.setWithLogicExpire(key, r1, time, unit);
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
//释放锁
unLock(lockKey);
}
});
}
//7.获取失败,返回旧数据
return r;
}
private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
//获取锁
private boolean tryLock(String key) {
Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", LOCK_SHOP_TTL, TimeUnit.SECONDS);
return BooleanUtil.isTrue(flag);
}
//释放锁
private void unLock(String key) {
stringRedisTemplate.delete(key);
}
}
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