Details
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Bug
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Status: Closed
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Major
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Resolution: Won't Fix
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10.2.2.0
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None
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None
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Ubuntu 6.10, Java 5 and Mac OSX 10.4, Java5
Spring 2.x
Derby "Embedded" mode
Description
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 type.
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.