Types.NULL is not accepted when using setNull on a PreparedStatment
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Key: DERBY-2550
URL: https://issues.apache.org/jira/browse/DERBY-2550
Project: Derby
Issue Type: Bug
Components: JDBC
Affects Versions: 10.2.2.0
Environment: Ubuntu 6.10, Java 5 and Mac OSX 10.4, Java5
Spring 2.x
Derby "Embedded" mode
Reporter: Christian Schwanke
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.
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