在Java中设置异常原因 [英] Setting an exception cause in Java

问题描述

我看到捕获了一个可以打印e.getCause()的异常，尽管它总是null.

I can see on catching an exception that I can print e.getCause(), though it is always null.

我是否需要将其设置在某个地方，或者缺少将原因设置为null的东西?

Do I need to set it somewhere, or is something missing which is setting the cause to null?

推荐答案

异常具有属性message和cause.该消息是一种描述，或多或少准确地告诉人类读者出了什么问题. cause有所不同:它是另一个(嵌套的)Throwable(如果有).

An Exception has the attributes message and cause. The message is a description, telling a human reader more or less exactly, what went wrong. The cause is something different: it is, if available, another (nested) Throwable.

如果我们使用这样的自定义异常，通常会使用该概念:

The concept is often used if we use custom exceptions like this:

catch(IOException e) {
  throw new ApplicationException("Failed on reading file soandso", e);
  //                              ^ Message                        ^ Cause
}

针对 djangofan的评论:

标准是嵌套表达式(原因)也将打印其堆栈跟踪信息.

The standard is that the nested expression (the cause) is printed with its stack trace too.

运行这个小应用程序

public class Exceptions {
    public static void main(String[] args) {
        Exception r = new RuntimeException("Some message");
        throw new RuntimeException("Some other message", r);
    }
}

将输出

Exception in thread "main" java.lang.RuntimeException: Some other message
    at Exceptions.main(Exceptions.java:4)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: java.lang.RuntimeException: Some message
    at Exceptions.main(Exceptions.java:3)
    ... 5 more

两个消息都包括在内.

这篇关于在Java中设置异常原因的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！