Support optional parameters in stored procedures

[mwisnicki]

As per https://stackoverflow.com/questions/13162043/spring-simplejdbccall-default-optional-arguments there seems to be no straightforward way to call stored procedure with optional parameters.

I would expect there to be something like SqlDefaultParamaterValue for explicit binding to default value (in SQL Server this would generate DEFAULT).
Additionally SimpleJdbcCall should do it automatically for missing parameters based on metadata (COLUMN_DEF)

[mwisnicki]

The latter part seems to be a deficiency of JDBC drivers - microsoft/mssql-jdbc#553 but looks like it's also a problem in postgres so it would be great if spring-jdbc did the right thing to make it work in every case.

[mwisnicki]

I'm not sure how IntelliJ's database code is dealing with it but somehow they let me use placeholder param and allow setting DEFAULT in parameter binding form.

[sbrannen]

I've labeled this as pending design work for possible inclusion in 5.3.x.

Brainstorming idea from @jhoeller: maybe there could be a DEFAULT_VALUE constant on SqlParameterValue rather than a subclass.