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From "Ivanov, Alexey A" <alexey.a.iva...@intel.com>
Subject [classlib][swing] compatibility: j.s.text.GapContent.replace() behaviour
Date Thu, 02 Nov 2006 09:09:28 GMT
Hi all,

I've started fixing HARMONY-1809. To remove throws clause from the
declaration of replace method, as it was proposed by Oleg in
HARMONY-1975, I placed removeItems() and insertItems() calls into
try-catch block. This would work OK for any valid arguments.

I was going to handle invalid arguments by making adjustments so that
the following removeItems() and insertItems() will not throw the
exception. After I wrote several tests, I faced strange behaviour of RI
with regards to invalid arguments to replace.

(The Javadoc say nothing about which valid ranges for replace()
parameters as well as any exceptions.)

RI accepts invalid arguments but the result differs from what I'd
expect.
For example, if the content has "text" in it, I'd expect that
content.replace(-2, 4, null, 0) would give "xt" as the result. I mean
the invalid start position is adjusted to 0, and the length of remove is
adjusted to be 2 accordingly. But this is not the case. As the result of
this call, all characters are removed leaving "" in the content.

Moreover the content object becomes unusable after that:
content.insertString(0, "1") throws ArrayIndexOutOfBoundsException.

Similarly if number of characters to be removed is greater than the
length of the content (content.replace(2, 4, null, 0) with "text" in
it), the object will throw ArrayIndexOutOfBoundsException when doing
insertString.


Considering the fact that GapContent is pretty low-level class in text
representation model and that it is protected, I think that Harmony
implementation can silently ignore BadLocationException possible thrown
from insertItems() and removeItems(). Taking into account erroneous
behaviour of RI's replace, we can do that until an application is
broken.

As another option, we can throw an Error from catch block to make
application which depends on implementation of replace() fast-fail.


Any objections, comments, opinions?

Thanks,
Alexey.


P.S. The related JIRA issues:
https://issues.apache.org/jira/browse/HARMONY-1809
https://issues.apache.org/jira/browse/HARMONY-1975

GapContent Javadoc:
http://java.sun.com/j2se/1.5.0/docs/api/javax/swing/text/GapContent.html
Description of GapContent.replace:
http://java.sun.com/j2se/1.5.0/docs/api/javax/swing/text/GapContent.html
#replace(int,%20int,%20java.lang.Object,%20int)


--
Alexey A. Ivanov
Intel Middleware Product Division

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