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

避免抛出异常的主要原因是抛出异常涉及大量开销。

下面这篇文章指出的一件事是，例外是针对异常条件和错误的。

错误的用户名不一定是程序错误，而是用户错误……

下面是关于。net中的异常的一个不错的起点: http://msdn.microsoft.com/en-us/library/ms229030 (VS.80) . aspx

安全性与您的示例混为一谈:您不应该告诉攻击者用户名存在，但密码是错误的。这是你不需要分享的额外信息。只要说“用户名或密码不正确”。

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.

我想说的是，如果发生了意想不到的行为，应该抛出异常。

比如试图更新或删除一个不存在的实体。它应该在异常可以处理并且有意义的地方被捕获。如果要以另一种方式继续工作，请在Api级别上添加日志记录或返回特定的结果。

如果您期望某些事情是这样的，那么您应该构建代码来检查并确保它是正确的。

在决定异常是否合适时，需要考虑一些有用的事情:

what level of code you want to have run after the exception candidate occurs - that is, how many layers of the call stack should unwind. You generally want to handle an exception as close as possible to where it occurs. For username/password validation, you would normally handle failures in the same block of code, rather than letting an exception bubble up. So an exception is probably not appropriate. (OTOH, after three failed login attempts, control flow may shift elsewhere, and an exception may be appropriate here.) Is this event something you would want to see in an error log? Not every exception is written to an error log, but it's useful to ask whether this entry in an error log would be useful - i.e., you would try to do something about it, or would be the garbage you ignore.