This was covered in either/both of the ND 3->4 migration course and the ND
3->4 conversion guide
You wrote breakable code. Sometimes breakable code breaks, and sometimes
it doesn't.
If X is an abstract class that is extended by concrete classes X1, X2, X3,
etc., and there is a method getX() that returns an object of class X, it
could be any one of the concrete classes. In fact, it might even be an
anonymous inner class that you've never heard of. If you just cast the
return to X1 without checking, and, if it is X1, then stuff will work. If
it is not X1, then a class cast exception will be thrown.
In ND3, 99% of the time, methods that returned CSpValues actually returned
CSpStrings. But there was never a guarantee that you would get a CSpString
and not a CSpInteger or whatever. In ND4, you are getting more returns
that are not CSpStrings. It has to do with the new architecture that
employs tndValues and stuff (not well documented IMHO) under the hood.
I would also suggest that you look at how you are using CSpValues in
general. There's not much point to them, any more. I'm hoping that in the
future ND will give us the option of using Object (and its children String,
Integer, Vector, etc.) instead of CSpValue. If you need to deal with a
CSpValue as a specific concrete extension (e.g. CSpString), think about
just using the generic java equivalent (e.g. String), instead.
-- Curt Springer, Team ND
At 07:19 AM 4/16/99 -0800, Pat_ORourke wrote:
>Curt,
>
>Thanks for that. That appeared to work fine. However, would you have any
idea why the previous
>casting code would work in ND3 and not in ND4. I am currently migrating an
ND3 project to ND4 and the
>casting that I described earlier is dotted all over the place and this
would involve quite of lot
>of searching and replacing if this is the case.
>
>Thanks,
>Pat.
>
>Curt Springer <[EMAIL PROTECTED]> wrote:
>>At least in this instance, your method is returning a CSpValue that
is>_not_ a CSpString.
>>
>>If you want to guarantee that you get a CSpString result, you would have to
>>do:
>>CSpString min = new CSpString(fdMinInputSizeBank.get( fieldName )
>>.stringValue());
>>
>>If you have reason to believe that the method would actually return a
>>CSpString a good deal of the time, and don't want to incur the overhead of
>>instantiating a new one all the time, you could test:
>>CSpValue min1 = ( fdMinInputSizeBank.get( fieldName ));
>>CSpString min = min1 instanceof CSpString ? min1 : new
>>CSpString(min1.stringValue());
>>
>>-- Curt Springer, Team ND
>>
>>At 05:15 AM 4/16/99 -0800, Pat_ORourke wrote:
>>>I am trying to cast a CSpValue to a CSpString and the below code is giving
>>me the following error.
>>>
>>>'Unexpected Exception (java.lang.ClassCastException:
>>spider.session.CSpLong) caught.
>>>Top of stack: |java.lang.ClassCastException: spider.session.CSpLong'
>>>
>>>
>>>// Exception thrown here
>>>CSpString min = (CSpString) (fdMinInputSizeBank.get( fieldName ) );
>>>
>>>// I placed this debug code in the function to check that a value exists.
>>>// This prints the value from the database table (eg '10') to the log
>>file with no exception
>>>CSpValue min1 = ( fdMinInputSizeBank.get( fieldName ));
>>>CSpLog.send( "pgBoResellerDetails", CSpLog.ERROR, min1 );
>>>
>>>
>>>(Aside : fdMinInputSizeBank is a hash table that stores the minimum value
>>>for a particular field)
>>>
>>>Any ideas would be appreciated,
>>>Thanks,
>>>Pat.
>>>_________________________________________________________________________
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>>>
>
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