To my mind, the fundamental question should be whether one would expect that the caller would want to continue normal program flow if a condition occurs. If you don't know, either have separate doSomething and trySomething methods, where the former returns an error and the latter does not, or have a routine that accepts a parameter to indicate whether an exception should be thrown if it fails). Consider a class to send commands to a remote system and report responses. Certain commands (e.g. restart) will cause the remote system to send a response but then be non-responsive for a certain length of time. It is thus useful to be able to send a "ping" command and find out whether the remote system responds in a reasonable length of time without having to throw an exception if it doesn't (the caller would probably expect that the first few "ping" attempts would fail, but one would eventually work). On the other hand, if one has a sequence of commands like:

  exchange_command("open tempfile");
  exchange_command("write tempfile data {whatever}");
  exchange_command("write tempfile data {whatever}");
  exchange_command("write tempfile data {whatever}");
  exchange_command("write tempfile data {whatever}");
  exchange_command("close tempfile");
  exchange_command("copy tempfile to realfile");

人们会希望任何操作的失败都能中止整个序列。虽然可以检查每个操作以确保操作成功，但如果命令失败，让exchange_command()例程抛出异常会更有帮助。

实际上，在上面的场景中，有一个参数来选择一些失败处理模式可能会有所帮助:从不抛出异常，仅为通信错误抛出异常，或者在命令没有返回“成功”指示的任何情况下抛出异常。

异常类就像“正常”类。当一个新类“是”一个不同类型的对象，具有不同的字段和不同的操作时，您可以创建一个新类。

As a rule of thumb, you should try balance between the number of exceptions and the granularity of the exceptions. If your method throws more than 4-5 different exceptions, you can probably merge some of them into more "general" exceptions, (e.g. in your case "AuthenticationFailedException"), and using the exception message to detail what went wrong. Unless your code handles each of them differently, you needn't creates many exception classes. And if it does, may you should just return an enum with the error that occured. It's a bit cleaner this way.

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

一个经验法则是在您通常无法预测的情况下使用异常。例如数据库连接、磁盘上丢失的文件等。对于您可以预测的场景，例如用户试图使用错误的密码登录，您应该使用返回布尔值的函数，并知道如何优雅地处理这种情况。您不希望仅仅因为有人输入了密码错误而抛出异常，从而突然结束执行。

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)。

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”。