java - 在所有内部异常中查找特定类型的自定义异常

Question

我正在尝试从顶级异常中递归查找所有内部异常(getCause 的)...特定实例类型。

public class MyCustomRunTimeException extends RuntimeException {

    public MyCustomRunTimeException() {
    }

    public MyCustomRunTimeException(Exception innerException) {
        super(innerException);
    }
}

这是我尝试过的:

和我早期的“查找”方法:

private void findAllSpecificTypeOfInnerExceptions(Exception ex)
{

            Collection<MyCustomRunTimeException> MyCustomRunTimeExceptions = Stream.iterate(ex, Throwable::getCause)
                    .filter(element ->
                            element != null
                                    && element instanceof MyCustomRunTimeException
                    )
                    .map(obj -> (MyCustomRunTimeException) obj)
                    .collect(Collectors.toList());

}

它不起作用。 :( 我已经尝试了其他几种方法(尚未显示)......如果我得到任何不会引发异常的东西，我会将它们作为“附加”发布到这个问题。不工作....我收到 NullPointers 异常。和(取决于我的调整)java.lang.reflect.InvocationTargetException 异常。

下面是一些可以找到 1:N“匹配项”的示例。

    Exception exampleOne = new MyCustomRunTimeException();

    Exception exampleTwo = new Exception(new MyCustomRunTimeException());

    Exception exampleThree =new Exception(new Exception(new MyCustomRunTimeException()));

    Exception exampleFour =new Exception(new Exception(new MyCustomRunTimeException(new ArithmeticException())));

Answer 1

在这种情况下，我真的认为在循环中执行递归位比完全使用流更简单:

List<Throwable> exlist = new ArrayList<>();
while(ex.getCause()!=null) {
    exlist.add(ex.getCause());
    ex = ex.getCause();
}
exlist = exlist.stream().filter(e -> e instanceof MyCustomRunTimeException).collect(Collectors.toList());

在 Java 9+ 中有更好的选择，如果你使用外部库，但在核心 Java 8 中不是真的(黑客确实存在，但这使得它比上面的更不清楚，恕我直言，我真的不看到为此目的引入外部库是值得的。)

或者这个变体:

private <T extends Throwable> Collection<T> aggregateSubClassExceptions(Throwable inputEx, Class<T> type) {

    Collection<T> returnItems = new ArrayList<>();
    Throwable exc = inputEx;
    while (exc != null) {
        if (type.isInstance(exc)) {
            returnItems.add(type.cast(exc));
        }
        exc = exc.getCause();
    }

    return returnItems;
}

此代码获取特定类型和任何子类:

    Collection<MyCustomRunTimeException> testItOutCollection;



    Exception exampleOne = new MyCustomRunTimeException();
    Exception exampleTwo = new Exception(new MyCustomRunTimeException());
    Exception exampleThree = new Exception(new Exception(new MyCustomRunTimeException()));
    Exception exampleFour = new Exception(new Exception(new MyCustomRunTimeException(new ArithmeticException())));
    MyCustomRunTimeException exampleFive = new MyCustomRunTimeException(new MySubMyCustomRunTimeException(new MyCustomRunTimeException(new ArithmeticException())));

    testItOutCollection = this.aggregateSubClassExceptions(exampleOne, MyCustomRunTimeException.class);
    testItOutCollection = this.aggregateSubClassExceptions(exampleTwo, MyCustomRunTimeException.class);
    testItOutCollection = this.aggregateSubClassExceptions(exampleThree, MyCustomRunTimeException.class);
    testItOutCollection = this.aggregateSubClassExceptions(exampleFour, MyCustomRunTimeException.class);
    testItOutCollection = this.aggregateSubClassExceptions(exampleFive, MyCustomRunTimeException.class);