Talk about the pit of cache Boolean value

Preface

There is such a business scenario ： department A The service needs the user department B Business data of the service , department A Service user department B The business data precondition of the service is B The Department must give A to grant authorization .B The authorization and business data of the Department belong to different services . The request process is as follows

because A The request value of authentication information is fixed , Therefore, the probability of authentication results is also a fixed value . at that time B Business service development colleagues in the Department , In order to improve efficiency . Add cache , namely B Our business services will A Cache the authentication results . At that time, it was written as follows

 private final LoadingCache<String,Boolean> checkSvcCache = Caffeine            .newBuilder().maximumSize(Constants.MAX_SIZE)            .expireAfterWrite(Conastants.EXPIRE, TimeUnit.DAYS)            .build(key -> loadCache(key));    @Nullable    private Boolean loadCache(@NonNull String key) {        if(key.contains(Constant.UNDER_LINE)){            try {                String[] arr = key.split(Constant.UNDER_LINE);                Integer ak = Integer.parseInt(arr[0]);                String sk = arr[1];                RPCResult<Boolean> result = authService.checkSvc(ak, sk);                if(result.getSuccess()){                    Boolean data = result.getData();                    return data;                }                return false;            } catch (Exception e) {                log.error("{}",e);            }        }        return false;    }

reflection

Let's see if there is any problem with the writing of the above code block ？

At first glance, there seems to be no problem , But there is actually a little problem . When making a remote call , If there is an anomaly , The Boolean will return false. In this way, the correct result may be covered up , For example, they all follow the agreement ak,sk It's worth it , Result: authentication failed .

Repair

How to fix it ？ A little philosophical stuff , The world is not black or white , In fact, there may still be gray areas . Boolean values are in java In the world of , It's not just true perhaps false, When the Boolean value is a wrapper class , He also has a state of null. So it can be changed to

@Nullable    private Boolean loadCache(@NonNull String key) {        if(key.contains(Constant.UNDER_LINE)){            try {                String[] arr = key.split(Constant.UNDER_LINE);                Integer ak = Integer.parseInt(arr[0]);                String sk = arr[1];                RPCResult<Boolean> result = authService.checkSvc(ak, sk);                if(result.getSuccess()){                    Boolean data = result.getData();                    return data;                }                return false;            } catch (Exception e) {                log.error("{}",e);            }        }        return null;    }

But is there no problem with this change , In fact, there are still problems , because null The value is not the correct result . But we can use null To do some extra abnormal disclosure . For example, it appears null when , There's just a problem , We can A Give friendly tips , Instead of returning authentication failure , It is also convenient to expose problems in advance , And the next time you ask to come in , The cache will be because the value is null, Trigger the remote call again

summary

Abnormal process thinking is important ...