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From: Knut Anders Hatlen <knut.hatlen@oracle.com>
To: Tim Dudgeon <tdudgeon@informaticsmatters.com>
Cc: derby-user@db.apache.org
Subject: Re: varargs with functions
References: <l8ul9v$165$1@ger.gmane.org>
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Date: Thu, 19 Dec 2013 14:20:23 +0100
In-Reply-To: <l8ul9v$165$1@ger.gmane.org> (Tim Dudgeon's message of "Thu, 19
	Dec 2013 11:29:17 +0000")
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Tim Dudgeon <tdudgeon@informaticsmatters.com> writes:

> I'm struggling with getting a function working that uses a Java static
> method that uses varargs.
> I understand this should work with 10.10.1.1?
>
> I create function like this:
>
> CREATE FUNCTION FORMAT_CPD_CODE
> ( FORMAT VARCHAR(100), VAL INT ... )
> RETURNS VARCHAR(20)
> PARAMETER STYLE DERBY
> NO SQL LANGUAGE JAVA
> EXTERNAL NAME 'java.lang.String.format'
>
> and use it like this:
>
> values(FORMAT_CPD_CODE('XYZ%08d', 123))
>
>
> But I get error:
>
> java.sql.SQLSyntaxErrorException: No method was found that matched the
> method call java.lang.String.format(java.lang.String, int...), tried
> all combinations of object and primitive types and any possible type
> conversion for any  parameters the method call may have. The method
> might exist but it is not public and/or static, or the parameter types
> are not method invocation convertible.
>
> Any suggestions on how to get this working?

Hi Tim,

Derby's method resolution currently requires the types in the signature
to match exactly. That is, it doesn't accept Object for an INT
parameter; it has to be int or java.lang.Integer. I think it should work
if you create a thin wrapper method around String.format() with the
correct signature. Something like this:

    public static String format(String format, Integer... args) {
        return String.format(format, (Object[]) args);
    }

And then point to the wrapper method in the CREATE FUNCTION call.

Hope this helps,

-- 
Knut Anders