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Date: Tue, 19 May 2009 13:49:22 +0200
From: Kristian Waagan <Kristian.Waagan@Sun.COM>
Subject: Re: Problems create SQL Function
In-reply-to: <23614219.post@talk.nabble.com>
Sender: Kristian.Waagan@Sun.COM
To: Derby Discussion <derby-user@db.apache.org>
Message-id: <4A129CC2.8010708@Sun.COM>
References: <23595863.post@talk.nabble.com> <4A1156B1.3000501@Sun.COM>
 <23614219.post@talk.nabble.com>
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dacia wrote:
> Hi Kristian
> 
> I tried this:
> 
> java code:
> public class DateFunctions {
> 
>   public static java.util.Date getDate(long instant) {
>       return new java.util.Date(instant);
>   }
> }
> 
> in ij:
> ij>call sqlj.install_jar('DateFunctions.jar','DateFunctions',0);
> Statement executed.
> ij> create function getDate(timeNumber bigint) returns date
>> language java external name
>> 'DateFunctions.getDate'
>> parameter style java no sql;
> 0 rows inserted/updated/deleted
> 
> ij>values getDate(123456789123456789);
> ERROR 42X50: No method was found that matched the method call
> DateFunctions.getDate(long), 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.

Would be good if also the expected return type was included in the error 
message here...

> 
> ij>values getDate(Cast(123456789123456789 as bigint));
> ERROR 42X50:......
> 
> ij>select s.schemaname, f.filename
>> from sys.sysschemas s, sys.sysfiles f
>> where s.schemaid=f.schemaid; 
> SCHEMANAME | FILENAME                                                                                                                        
> APP |DATEFUNCTIONS                                                                                                                   
> 1 row selected
> 
> Is there any way to verify, if the function is loaded and which parameters
> are expected ?

Not that I'm aware of, except for looking in the system tables. Anyone?

> Or what did I wrong ?

Sorry, I didn't think about the fact that you have to return a data type 
that Derby can handle (SQL). These are described in the Reference Manual 
under "Data types".

In this case, java.util.Date was specified, but one of java.sql.Date, 
java.sql.Time or java.sql.Timestamp should be used.

I had no problems invoking the function when doing that. I didn't create 
a Jar, just put the class on the classpath:

ij version 10.6
ij> connect 'jdbc:derby:memory:mydb;create=true';
ij> create function getDate(timeNumber bigint) returns date
 > language java external name
 > 'DateFunctions.getDate'
 > parameter style java no sql;
0 rows inserted/updated/deleted
ij> values getDate(23423423432);
1
----------
1970-09-29

1 row selected
ij>


Cheers,
-- 
Kristian

> 
> 
> 
> 
> Kristian Waagan-4 wrote:
>> dacia wrote:
>>> Hi there
>>>
>>> I try to create some SQL function, but I stuck:
>>>
>>> [code]
>>> create function getDate(timeNumber bigint) returns date
>>>   
>>>> language java external name
>>>> 'java.util.Date(time)'
>>>> parameter style java no sql;
>>>>     
>>> 0 rows inserted/updated/deleted
>>> [/code]
>>>
>>> now:
>>>
>>> [code]
>>> ij> values getDate(1234566712345667789);
>>> ERROR 42X51: The class 'java.util' does not exist or is inaccessible.
>>> This
>>> can happen if the class is not public.
>>> ERROR XJ001: Java exception: 'java.util:
>>> java.lang.ClassNotFoundException'.
>>> [/code]
>>>
>>>
>>> What is wrong ?
>>>   
>> Hi,
>>
>> You have to specify a public static method as the external name.
>> In the code you posted, Derby tries to find the class java.util and the 
>> static method Date. Since there is no such class nor method, it fails.
>>
>> Unless you find a public static method in the Java API that returns a 
>> Date, I think you need to write your own wrapper method, for instance:
>> public class MyClass {
>>     public static java.util.Date getDate(long instant) {
>>        return new java.util.Date(instant);
>>     }
>> }
>>
>> The external name here would be 'MyClass.getDate', or 
>> 'MyClass.getDate(long)' (I think).
>> Note that the method doesn't need to have the same name as the function 
>> you declare. The class you write has to be on the classpath for Derby to 
>> access it (unless you install a Jar file in the database).
>>
>>
>> Hope this helps,
>> -- 
>> Kristian
>>
>>>  Thanx
>>>   
>>
>>
>