在Java中捕获通用异常？ [英] Catch a generic exception in Java?

问题描述

我们在工作中使用JUnit 3，没有 ExpectedException 注释。我想在我们的代码中添加一个实用程序来包装：

We use JUnit 3 at work and there is no ExpectedException annotation. I wanted to add a utility to our code to wrap this:

 try {
     someCode();
     fail("some error message");
 } catch (SomeSpecificExceptionType ex) {
 }

所以我试过这个：

public static class ExpectedExceptionUtility {
  public static <T extends Exception> void checkForExpectedException(String message, ExpectedExceptionBlock<T> block) {
     try {
        block.exceptionThrowingCode();
        fail(message);
    } catch (T ex) {
    }
  }
}

但是，Java不能在catch块中使用泛型异常类型。

However, Java cannot use generic exception types in a catch block, I think.

如何处理Java限制？

How can I do something like this, working around the Java limitation?

有没有办法检查 ex 变量是否类型为 T ？

Is there a way to check that the ex variable is of type T?

推荐答案

您可以传递Class对象，并以编程方式检查。

You could pass the Class object in and check that programatically.

public static <T extends Exception> void checkForException(String message, 
        Class<T> exceptionType, ExpectedExceptionBlock<T> block) {
    try {
       block.exceptionThrowingCode();
   } catch (Exception ex) {
       if ( exceptionType.isInstance(ex) ) {
           return;
       } else {
          throw ex;  //optional?
       }
   }
   fail(message);
}

//...
checkForException("Expected an NPE", NullPointerException.class, //...

我不知道你是否想要重新抛出;推翻会同样失败/错误的测试，但语义上我不会，因为它基本上意味着我们没有得到我们预期的异常，所以代表一个编程错误，而不是测试环境错误。

I'm not sure if you'd want the rethrow or not; rethrowing would equally fail/error the test but semantically I wouldn't, since it basically means "we didn't get the exception we expected" and so that represents a programming error, instead of a test environment error.

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