I need to clarify the first statement that I made in my previous post (see below). I claim that parameter sqlType in method PreparedStatement.setNull(int parameterIndex, int sqlType) is redundant because a NULL SQL parameter has no intrinsic type. A NULL SQL value applies to any column type, so it is unnecessary to identify its type.
Derek -----Original Message----- From: Derek Mahar Sent: May 20, 2004 2:08 PM To: Tag Libraries Users List Subject: RE: [JSTL] How do I enter a null value with <sql:param>? Thank you. I appreciate your attention and quick response. After reading JDBC Specification Section 13.2.2.3, Setting NULL Parameters, I understand now why Kris suggested that the JSTL specification add the sqlType attribute to <sql:param>: method PreparedStatement.setNull(int parameterIndex, int sqlType) requires the type of the parameter that you want to set to NULL. However, why does method setNull require this parameter? A NULL parameter has no intrinsic type! In order to determine the "type" of a NULL parameter, you must consider its expression or assignment context. That is, in order to determine the "type" of a NULL parameter, must consider the type of the column to which you are assigning the parameter in a SET clause or the column or literal value to which you are comparing the parameter in a WHERE clause. Or, you must assign it a type using a new attribute like sqlType. According to JDBC Specification Section 13.2.3, Describing Outputs and Inputs of a PreparedStatement Object, ParameterMetaData.getParameterMetaData(int param) returns the type of each parameter in a parameterized query. What "type" does this method return for a NULL parameter? If it does, in fact, return a NULL parameter's contextual type, then I can change the <sql:param> implementation so that it invokes PreparedStatement.setNull instead of PreparedStatement.setObject for NULL parameters. Otherwise, I cannot see how I can supply setNull with a correct "type". Consequently, I'll just have to wait for Microsoft to fix its JDBC driver so that it correctly handles the case PreparedStatement.setObject(index,null). Derek -----Original Message----- From: Justyna Horwat [mailto:[EMAIL PROTECTED] Sent: May 20, 2004 1:10 PM To: Tag Libraries Users List Subject: Re: [JSTL] How do I enter a null value with <sql:param>? Derek, I forwarded your comments to the JDBC specification lead. He said that now is a good time to bring up all of these annoyances in the specification. He will look into clarifying this area in the upcoming version of the spec. Thanks, Justyna Derek Mahar wrote: > After reading Section 17.7 of the JDBC specification (available at > http://java.sun.com/products/jdbc/download.html), I now agree that > there is a problem with the Microsoft SQL JDBC driver, but there is > also a problem with the official Java JDBC API documentation that does > not mention how PreparedStatement.setObject() handles the case > PreparedStatement.setObject(index, null). I guess we should ask Sun > to correct (or complete) its JDBC API documentation and I need to ask > Microsoft to fix its JDBC driver. > > However, I still need to fix my problem now. So, as I have Standard > Tag Library source code, but do not have the source of the Microsoft > SQL Server JDBC driver, I will likely change the <sql:param> > implementation so that it invokes PreparedStatement.setNull() when it > receives a null value. Here is a perfect case where having source > code is of tremendous benefit. > > Thank you for pointing me in the right direction and being patient > with my posts as I worked through my problem. > > Derek > > -----Original Message----- > From: Wolfgang Röckelein > [mailto:[EMAIL PROTECTED] > Sent: May 19, 2004 10:40 AM > To: Tag Libraries Users List > Subject: Re: [JSTL] How do I enter a null value with <sql:param>? > > > Keith wrote: > >>This was on the Users list and was my problem. But mine had to do >>specifically with the <sql:dateParam> and the Oracle JDBC driver. The >>regular <sql:param> worked fine for me when I passed it a null value. >> >>Link to the starting thread in the archive: >>http://www.mail-archive.com/[EMAIL PROTECTED]/msg06748.h >>tml > > > Thanks for digging this out. Both problems boil down to the case that > "when setObject(index, null) is passed in a null value this should be converted > by the driver to an SQL null" does not work with the JDBC driver (perhaps only > for certain data types, which could be the cause why you see it only with > <sql:dateParam>). From my experience I know that the MS SQL JDBC driver has/had > problems in this area... > > Regards, > Wolfgang > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > > NOTICE: This email contains privileged and confidential information > and is intended only for the individual to whom it is addressed. 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