我们可以在抛出中使用泛型异常吗？

Question

I have a silly doubt. While using throws I know we specify multiple exceptions. My query is can we include Exception (generic) also along with other specific exceptions? Is that right coding approach?

public String display() throws IOException, FileNotFoundException, Exception {
    ...
}

Here using Exception is right approach??

Answer 1

It is legal code.

It is a bad idea.

The reason that it is a bad idea is that the caller now has to handle (or propagate) Exception . But an Exception could be almost anything. How can you do anything sensible ¹ with an exception in an exception handler if you don't know what it could be?

I would argue that if you don't know what the cause of an exception is, the only totally safe thing you can do is to log it and terminate the application. In some contexts you could try to log the exception, "fail" the request and carry on with the next one. That may be a sensible strategy, if service availability is the highest priority, and the system is designed to be robust (eg idempotent requests, transactional implementation). However, there is a risk that this approach will increase the damage. But the problem with throwing Exception is that you make it much harder to discriminate between errors that are recoverable and those that are not.

Answer 2

It is legal Java code.

First part for the usage of Exception in throws declaration.

It should seldom be written in production code, before it suggests that the method could throw absolutely any checked exception, which is quite uncommon.

But it is currently used in Junit tests. The aim of a test function is to test one single feature, and should be as simple as possible because it is expected to not contain logic errors. So it is common to write the test as:

@Test
public void testFeature() throws Exception {
    //actual test that can call any function declaring checked exception
}

Here this just means that you do not want to worry for possible exception declared in functions used in the test body.

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But your code declares Exception in addition to other exception (sub-)classes. That is useless because all exception classes are subclasses of Exception , thus IOException and FileNotFoundException are Exception s.

So even if legal, this does not make sense: if you put Exception in throws declaration, you should remove all other exception classes because they are already contained in the Exception declaration.

Answer 3

In my opinion method can throw generic Exception, when you business logic and your pipeline works like application has to continue work even after fatal error, log this error as FFDC and continue works. If your application has to shutdown after fatal eror, then your method has not to throw generic Exception.