如何附加到 Java 异常？
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How do I append to a Java exception?
提问by kevinarpe
I am new to Java and exceptions in general.
我对 Java 和一般的异常不熟悉。
In my prior C/Perl programming days, when I wrote a library function, errors were passed back by a boolean flag, plus some kind of string with a human-friendly (or programmer-friendly) error message. Java and C++ have exceptions, which is handy because they include stack traces.
在我之前的 C/Perl 编程时代，当我编写一个库函数时，错误通过一个布尔标志传回，加上某种带有人类友好（或程序员友好）错误消息的字符串。Java 和 C++ 有异常，这很方便，因为它们包含堆栈跟踪。
I often find when I catch an exception, I want to add my two cents, then pass it along.
我经常发现，当我捕获异常时，我想添加我的两分钱，然后传递它。
How can this be done? I don't want to throw away the whole stack trace... I don't know how deep the failure occurred and for what reason.
如何才能做到这一点？我不想扔掉整个堆栈跟踪......我不知道失败发生的深度和原因。
I have a little utility library to convert a stack track (from an Exception object) into a string. I guess I could append this to my new exception message, but it seems like a hack.
我有一个小实用程序库来将堆栈轨道（从异常对象）转换为字符串。我想我可以将它附加到我的新异常消息中，但这似乎是一种黑客攻击。
Below is an example method. Advices?
下面是一个示例方法。建议？
public void foo(String[] input_array) {
for (int i = 0; i < input_array.length; ++i) {
String input = input_array[i];
try {
bar(input);
}
catch (Exception e) {
throw new Exception("Failed to process input ["
+ ((null == input) ? "null" : input)
+ "] at index " + i + ": " + Arrays.toString(input_array)
+ "\n" + e);
}
}
}
回答by axtavt
Exceptions can be chained:
异常可以被链接：
try {
...
} catch (Exception ex) {
throw new Exception("Something bad happened", ex);
}
It makes original exception the causeof the new one. Cause of exception can be obtained using getCause(), and calling printStackTrace()on the new exception will print:
它使原始异常成为新异常的原因。可以使用 获取异常原因getCause()，调用printStackTrace()新异常将打印：
Something bad happened ... its stacktrace ... Caused by: ... original exception, its stacktrace and causes ...
回答by Jon Skeet
Typically you throw a new exception which includes the oldexception as a "cause". Most exception classes have a constructor which accept a "cause" exception. (You can get at this via Throwable.getCause().)
通常，您会抛出一个新异常，其中包含旧异常作为“原因”。大多数异常类都有一个接受“原因”异常的构造函数。（您可以通过 获得此信息Throwable.getCause()。）
Note that you should almost never be catching just Exception- generally you should be catching a more specific type of exception.
请注意，您几乎永远不应该只捕获Exception- 通常您应该捕获更具体类型的异常。
回答by Andreas Dolk
Just use a different constructor:
只需使用不同的构造函数：
Exception(String message, Throwable cause)
The message is your "two cent" and you include the catched exception, which will be shown in a stacktrace printout
该消息是您的“两分钱”，您包括捕获的异常，该异常将显示在堆栈跟踪打印输出中
回答by Janick Bernet
You can add the underlying cause to a newly created exception:
您可以将根本原因添加到新创建的异常中：
throw new Exception("Failed to process input ["
+ ((null == input) ? "null" : input)
+ "] at index " + i + ": " + Arrays.toString(input_array)
+ "\n" + e.getMessage(), e);
