優(yōu)雅地處理重復(fù)請(qǐng)求（并發(fā)請(qǐng)求）

????String?KEY?=?"REQ12343456788";//請(qǐng)求唯一編號(hào)
????long?expireTime?=??1000;//?1000毫秒過(guò)期，1000ms內(nèi)的重復(fù)請(qǐng)求會(huì)認(rèn)為重復(fù)
????long?expireAt?=?System.currentTimeMillis()?+?expireTime;
????String?val?=?"expireAt@"?+?expireAt;

????//redis?key還存在的話要就認(rèn)為請(qǐng)求是重復(fù)的
????Boolean?firstSet?=?stringRedisTemplate.execute((RedisCallback)?connection?->?connection.set(KEY.getBytes(),?val.getBytes(),?Expiration.milliseconds(expireTime),?RedisStringCommands.SetOption.SET_IF_ABSENT));

????final?boolean?isConsiderDup;
????if?(firstSet?!=?null?&&?firstSet)?{//?第一次訪問(wèn)
????????isConsiderDup?=?false;
????}?else?{//?redis值已存在，認(rèn)為是重復(fù)了
????????isConsiderDup?=?true;
????}

????//兩個(gè)請(qǐng)求一樣，但是請(qǐng)求時(shí)間差一秒
????String?req?=?"{\n"?+
????????????"\"requestTime\"?:\"20190101120001\",\n"?+
????????????"\"requestValue\"?:\"1000\",\n"?+
????????????"\"requestKey\"?:\"key\"\n"?+
????????????"}";

????String?req2?=?"{\n"?+
????????????"\"requestTime\"?:\"20190101120002\",\n"?+
????????????"\"requestValue\"?:\"1000\",\n"?+
????????????"\"requestKey\"?:\"key\"\n"?+
????????????"}";

public?class?ReqDedupHelper?{

????/**
?????*
?????*?@param?reqJSON?請(qǐng)求的參數(shù)，這里通常是JSON
?????*?@param?excludeKeys?請(qǐng)求參數(shù)里面要去除哪些字段再求摘要
?????*?@return?去除參數(shù)的MD5摘要
?????*/
????public?String?dedupParamMD5(final?String?reqJSON,?String...?excludeKeys)?{
????????String?decreptParam?=?reqJSON;

????????TreeMap?paramTreeMap?=?JSON.parseObject(decreptParam,?TreeMap.class);
????????if?(excludeKeys!=null)?{
????????????List?dedupExcludeKeys?=?Arrays.asList(excludeKeys);
????????????if?(!dedupExcludeKeys.isEmpty())?{
????????????????for?(String?dedupExcludeKey?:?dedupExcludeKeys)?{
????????????????????paramTreeMap.remove(dedupExcludeKey);
????????????????}
????????????}
????????}

????????String?paramTreeMapJSON?=?JSON.toJSONString(paramTreeMap);
????????String?md5deDupParam?=?jdkMD5(paramTreeMapJSON);
????????log.debug("md5deDupParam?=?{},?excludeKeys?=?{}?{}",?md5deDupParam,?Arrays.deepToString(excludeKeys),?paramTreeMapJSON);
????????return?md5deDupParam;
????}

????private?static?String?jdkMD5(String?src)?{
????????String?res?=?null;
????????try?{
????????????MessageDigest?messageDigest?=?MessageDigest.getInstance("MD5");
????????????byte[]?mdBytes?=?messageDigest.digest(src.getBytes());
????????????res?=?DatatypeConverter.printHexBinary(mdBytes);
????????}?catch?(Exception?e)?{
????????????log.error("",e);
????????}
????????return?res;
????}
}

public?static?void?main(String[]?args)?{
????//兩個(gè)請(qǐng)求一樣，但是請(qǐng)求時(shí)間差一秒
????String?req?=?"{\n"?+
????????????"\"requestTime\"?:\"20190101120001\",\n"?+
????????????"\"requestValue\"?:\"1000\",\n"?+
????????????"\"requestKey\"?:\"key\"\n"?+
????????????"}";

????String?req2?=?"{\n"?+
????????????"\"requestTime\"?:\"20190101120002\",\n"?+
????????????"\"requestValue\"?:\"1000\",\n"?+
????????????"\"requestKey\"?:\"key\"\n"?+
????????????"}";

????//全參數(shù)比對(duì)，所以兩個(gè)參數(shù)MD5不同
????String?dedupMD5?=?new?ReqDedupHelper().dedupParamMD5(req);
????String?dedupMD52?=?new?ReqDedupHelper().dedupParamMD5(req2);
????System.out.println("req1MD5?=?"+?dedupMD5+"?,?req2MD5="+dedupMD52);

????//去除時(shí)間參數(shù)比對(duì)，MD5相同
????String?dedupMD53?=?new?ReqDedupHelper().dedupParamMD5(req,"requestTime");
????String?dedupMD54?=?new?ReqDedupHelper().dedupParamMD5(req2,"requestTime");
????System.out.println("req1MD5?=?"+?dedupMD53+"?,?req2MD5="+dedupMD54);

}

String?userId=?"12345678";//用戶
String?method?=?"pay";//接口名
String?dedupMD5?=?new?ReqDedupHelper().dedupParamMD5(req,"requestTime");//計(jì)算請(qǐng)求參數(shù)摘要，其中剔除里面請(qǐng)求時(shí)間的干擾
String?KEY?=?"dedup:U="?+?userId?+?"M="?+?method?+?"P="?+?dedupMD5;

long?expireTime?=??1000;//?1000毫秒過(guò)期，1000ms內(nèi)的重復(fù)請(qǐng)求會(huì)認(rèn)為重復(fù)
long?expireAt?=?System.currentTimeMillis()?+?expireTime;
String?val?=?"expireAt@"?+?expireAt;

//?NOTE:直接SETNX不支持帶過(guò)期時(shí)間，所以設(shè)置+過(guò)期不是原子操作，極端情況下可能設(shè)置了就不過(guò)期了，后面相同請(qǐng)求可能會(huì)誤以為需要去重，所以這里使用底層API，保證SETNX+過(guò)期時(shí)間是原子操作
Boolean?firstSet?=?stringRedisTemplate.execute((RedisCallback)?connection?->?connection.set(KEY.getBytes(),?val.getBytes(),?Expiration.milliseconds(expireTime),
????????RedisStringCommands.SetOption.SET_IF_ABSENT));

final?boolean?isConsiderDup;
if?(firstSet?!=?null?&&?firstSet)?{
????isConsiderDup?=?false;
}?else?{
????isConsiderDup?=?true;
}