Re: Exception handling

Lew <>
Wed, 2 Dec 2009 14:56:15 -0800 (PST)
Lew says...

You are mistaken. The LoD doesn't apply
here because exceptions are "neighbor" classes to the caller; chaining s=


retrieves multiple instances of those neighbor classes.

 Pitch wrote:

So you think PassswordException from user's Password-Service and
SqlException [sic] from JDBC are friend classes? :)

No, I think 'Throwable' is a "friend" type. 'getCause()' doesn't
return 'PasswordException' or 'SQLException'.

Citation from the Wiki page:

"an object should avoid invoking methods of a member object returned by
another method"

Since 'Throwable' is a friend, it's always OK to call methods on a

You've missed the point of LoD. Since the caller knows about
'Throwable' and that it has a 'getCause()' method, it is not reaching
into the member object's implementation to call 'getCause()' again,
therefore it is not violating LoD. It is using only the knowledge it
has of 'Throwable' to call 'getCause()' in a chain.

Anyway, 'getCause()' is far too useful to let foolish dogma restrict
one's use of it.


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