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https://issues.apache.org/jira/browse/IBATIS-494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12577589#action_12577589
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Jeff Butler commented on IBATIS-494:
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Interesting and convoluted.
Every type handler except the Blob and Clob type handlers call the "wasNull()"
function to determine if the returned value was null. This seems to me like
the proper way to fix this in the getResult() methods of those two type
handlers.
None of the other type handlers call the setNull() function, although I think
they probably should. For most other type handlers, there is other code in
iBATIS that does a null check before calling the type handler and calls the
appropriate setNull() function (see
com.ibatis.sqlmap.engine.mapping.parameter.ParameterMap, the setParameter
method). This check does not apply to the BLOB or CLOB handlers because they
turn out to be implementations of CustomTypeHandler.
Long story.
So, will you verify that calling wasNull() in the getResult() method works in
your instance (instead of the method you use in your patch)? See any other
type handler for an example of how to implement this. If it works (as I think
it should), I'll commit the change (and fix some of the other type handlers too
while I'm at it).
> ClobTypeHandlerCallback handles NULLs incorrectly
> -------------------------------------------------
>
> Key: IBATIS-494
> URL: https://issues.apache.org/jira/browse/IBATIS-494
> Project: iBatis for Java
> Issue Type: Bug
> Components: SQL Maps
> Affects Versions: 2.3.0
> Environment: WebSphere Application Server 6, DB2/390
> Reporter: Aaron Craven
> Attachments: ClobTypeHandlerCallback.diff
>
>
> After getting some very strange corruption issues with CLOBs in our
> production environment, I did some digging and I believe
> ClobTypeHandlerCallback to be improperly handling NULLs (though I'm not
> sure). The attached patch fixed our problem.
> Please note that I believe our corruption issues to be aggravated by a poorly
> implemented JDBC driver. I certainly don't think iBatis is corrupting our
> CLOB fields directly. But still, I believe these changes more properly handle
> values in CLOBs.
> There are two main modifications:
> - in getResult(), the method was defaulting to an empty string if the CLOB
> was null.
> - in setParameter, I replaced setString(null) with setNull(Types.CLOB), which
> I believe to be a more appropriate way to set a column to null in most
> drivers.
> As I said, I'm not a JDBC expert, so I could be wrong on these changes.
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