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From "Knut Anders Hatlen (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 09:16:18 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12489050

Knut Anders Hatlen commented on DERBY-2550:

Hi Christian,

This Spring issue has been discussed earlier. See this thread: http://mail-archives.apache.org/mod_mbox/db-derby-user/200607.mbox/%3ce8d7dh$5an$1@sea.gmane.org%3e

Note that Types.NULL identifies an SQL value (NULL), not an SQL type (http://java.sun.com/javase/6/docs/api/java/sql/Types.html#NULL).

> 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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