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From "Christian Schwanke (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2550) Types.NULL is not accepted when using setNull on a PreparedStatment
Date Mon, 16 Apr 2007 10:55:15 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12489074

Christian Schwanke commented on DERBY-2550:

sorry, I missed that one on the mailing list (although I searched quite a bit using the error
message on JIRA and the web :-()

The way I see it now, this error is not derby related but is some kind of spring-bug, since
using a sql-value-constant as a type parameter seems to be wrong (On the other hand, specifying
value-constants in a class named "Types" isn't consistent either :-))
Since this is not derby's fault, I'm closing this issue.

Thanks for your quick help!


> Types.NULL is not accepted when using setNull on a PreparedStatment
> -------------------------------------------------------------------
>                 Key: DERBY-2550
>                 URL: https://issues.apache.org/jira/browse/DERBY-2550
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC
>    Affects Versions:
>         Environment: Ubuntu 6.10, Java 5 and Mac OSX 10.4, Java5
> Spring 2.x
> Derby "Embedded" mode
>            Reporter: Christian Schwanke
>         Attachments: SimpleEmbeddedTestCase.java
> Inserting data into table using a PreparedStatement will fail, if the setNull() method
is used with Types.NULL.
> I have tracked down the problem to the method "isJDBCTypeEquivalent(int existingType,
int jdbcTypeId)" in class "org.apache.derby.iapi.types.DataTypeDescriptor" (Line 922).
> This method checks the current column type against the type specified by the application.
The setNull() method will throw an error, if the types do not match. The problem here is,
that isJDBCTypeEquivalent will not accept Types.NULL as an valid equivalent to the column
> When writing the JDBC code by hand one can avoid the problem - but this is quite annoying
since the Jdbc-Support provided by the Spring-Framework will use setNull() with Types.NULL
making it impossible to use Derby with Spring's plain JdbcTemplate.
> Example:
> String preparedSql = "INSERT INTO demo (stringValue) VALUES (?)";
> PreparedStatement pstmt = con.prepareStatement(preparedSql);
> // this will work, since the given type is equivalent
> pstmt.setString(1, null);
> pstmt.execute();
> // this will fail, since Types.NULL is not recognized as equivalent
> pstmt.setNull(1, Types.NULL);
> pstmt.execute();
> The exception thrown is 
> "java.sql.SQLException: An attempt was made to get a data value of type 'VARCHAR' from
a data value of type '0'"
> As far as I can see, it is sufficient to modify the first part of the isJDBCTypeEquivalent-method.
At least, it solved my problems.
> Current:
> 		// Any type matches itself.
> 		if (existingType == jdbcTypeId)
> 			return true;
> Fix:
> 		// Any type matches itself.
> 		if (existingType == jdbcTypeId || jdbcTypeId == Types.NULL)
> 			return true;
> I've attached a simple TestCase to reproduce the problem. 

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