我为我的应用程序不期望的每个条件创建了异常。UserNameNotValidException, PasswordNotCorrectException等。
然而,我被告知我不应该为这些条件创造例外。在我的UML中,那些是主要流程的异常,那么为什么它不应该是异常呢?
是否有创建异常的指导或最佳实践?
我为我的应用程序不期望的每个条件创建了异常。UserNameNotValidException, PasswordNotCorrectException等。
然而,我被告知我不应该为这些条件创造例外。在我的UML中,那些是主要流程的异常,那么为什么它不应该是异常呢?
是否有创建异常的指导或最佳实践?
当前回答
我有三种情况。
Bad or missing input should not be an exception. Use both client side js and server side regex to detect, set attributes and forward back to the same page with messages. The AppException. This is usually an exception that you detect and throw with in your code. In other words these are ones you expect (the file does not exist). Log it, set the message, and forward back to the general error page. This page usually has a bit of info about what happened. The unexpected Exception. These are the ones you don't know about. Log it with details and forward them to a general error page.
希望这能有所帮助
其他回答
首先,如果API的用户对特定的、细粒度的故障不感兴趣,那么为他们设置特定的异常就没有任何价值。
由于通常不可能知道什么可能对用户有用,一个更好的方法是有特定的异常,但确保它们继承自一个公共类(例如,std::exception或其在c++中的派生类)。这允许您的客户端捕获特定的异常(如果他们愿意的话),或者捕获更一般的异常(如果他们不关心的话)。
我认为只有在无法摆脱当前状态时才应该抛出异常。例如,如果您正在分配内存,但没有任何内存可以分配。在您提到的情况下,您可以清楚地从这些状态中恢复,并相应地将错误代码返回给调用者。
You will see plenty of advice, including in answers to this question, that you should throw exceptions only in "exceptional" circumstances. That seems superficially reasonable, but is flawed advice, because it replaces one question ("when should I throw an exception") with another subjective question ("what is exceptional"). Instead, follow the advice of Herb Sutter (for C++, available in the Dr Dobbs article When and How to Use Exceptions, and also in his book with Andrei Alexandrescu, C++ Coding Standards): throw an exception if, and only if
没有满足先决条件(通常会出现以下情况之一 不可能的)或 替代方案将无法满足后置条件或 替代方案将无法保持不变式。
为什么这样更好呢?它不是用几个关于前置条件,后置条件和不变量的问题代替了这个问题吗?这是更好的几个相关的原因。
Preconditions, postconditions and invariants are design characteristics of our program (its internal API), whereas the decision to throw is an implementation detail. It forces us to bear in mind that we must consider the design and its implementation separately, and our job while implementing a method is to produce something that satisfies the design constraints. It forces us to think in terms of preconditions, postconditions and invariants, which are the only assumptions that callers of our method should make, and are expressed precisely, enabling loose coupling between the components of our program. That loose coupling then allows us to refactor the implementation, if necessary. The post-conditions and invariants are testable; it results in code that can be easily unit tested, because the post-conditions are predicates our unit-test code can check (assert). Thinking in terms of post-conditions naturally produces a design that has success as a post-condition, which is the natural style for using exceptions. The normal ("happy") execution path of your program is laid out linearly, with all the error handling code moved to the catch clauses.
If it's code running inside a loop that will likely cause an exception over and over again, then throwing exceptions is not a good thing, because they are pretty slow for large N. But there is nothing wrong with throwing custom exceptions if the performance is not an issue. Just make sure that you have a base exception that they all inherite, called BaseException or something like that. BaseException inherits System.Exception, but all of your exceptions inherit BaseException. You can even have a tree of Exception types to group similar types, but this may or may not be overkill.
因此,简短的回答是,如果它不会导致显著的性能损失(除非抛出大量异常,否则不应该如此),那么就继续执行。
异常是一种代价高昂的效果,例如,如果您有一个用户提供了无效的密码,那么通常更好的方法是返回一个失败标志,或其他一些无效的指示。
这是由于异常处理的方式,真正的错误输入和唯一的关键停止项应该是异常,而不是失败的登录信息。
异常与返回错误代码参数应该是关于流控制的,而不是哲学(错误有多“异常”):
void f1() throws ExceptionType1, ExceptionType2 {}
void catchFunction() {
try{
while(someCondition){
try{
f1();
}catch(ExceptionType2 e2){
//do something, don't break the loop
}
}
}catch(ExceptionType1 e1){
//break the loop, do something else
}
}