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Re: Type of a generic class?

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  To: markspace
From: Donkey Hottie <donkey@fredriksson.dy.fi>

03.08.2012 00:08, markspace kirjoitti:
> On 8/2/2012 12:04 PM, Donkey Hottie wrote:
>
>> First problem I have is to translate the type to a lower level
>> application API call. I can not leave the cast or type conversion to
>> compiler only.
>
>
> I'm going to ignore other obvious problems and simply focus on the big
> picture here.  You idea how to accomplish this looks *TERRIBLE*.  Why
> aren't you using some kind of ORM?  At least use a light-weight library
> for translating data base entities into objects.
>

I am not trying to translate database tables to objects. I have an ORM for 
that.

I am trying to convert a simple { String name, String value } pair in database 
to a Global<T>(name) so that it will convert the Java simple datatypes to a 
string and back. This is for system parameters, configuration parameters.

It is indeed kind of spooky and strange idea, after all what is so wrong about 
simple

    String value = SystemProperties.getString("ParamName") ;

It is OK, but I'm kind of toying with idea of strong typing of System 
Parameters: A Date can not be stored as Long or Double etc..

The back end of the system parameters is simply

CREATE TABLE SystemParameters
(
    name varchar(64) not null primary_key,
    value varchar(512)
) ;

That's it. That is have the table is given to me. But I want to make the Java 
code bit more pedantic on the types of the parameters it uses and maintains.

This idea just occurred to me when I stubled against MUMPS language when 
learning InterSystems Ensemble. It is based on their Cacho NoSQL/SQL hybrid 
database, and while being an ancient language, MUMPS/M has lots of interesting 
features, including threading and database persistence in the old Programming 
Language Core!

I just thought I might as well copy their Global variable idea and include it 
in my toolbox of Java commons. It is not an ORM. I do not know about dbutils, 
but JPA I am very familiar with. It maps Java Objects to Relational Database 
records. There one attribute can have just one type. I want many types to my 
value attribute, but only for Java code. Just to force the apps to store at 
least correct type of values for properties, so that compiler stops my fellow 
programmer if he is about to generate a runtime error later somewhere, for 
example if he is trying to store 'NOW' for a value that is needed as Date.

Not a big deal, but this is my idea here.

> <http://commons.apache.org/dbutils/>
>
> Also JPA will do some kinds of automatic instantiation for you:
>
> <http://openjpa.apache.org/builds/1.0.4/apache-openjpa-1.0.4/docs/manual/jpa_
overview_mapping_inher.html>
>
>
> I didn't check to see if those are the most recent docs (I don't use
> this sort of feature).  Google for "JPA table inheritance" and check
> through the results carefully.
>
>
>> Class is a simple version containg only the important parts.
>
>
> Honestly, while we all appreciate the attempt, you example is far from
> complete.  We can guess at a few things, but you should think much more
> carefully at what the real problem is and design something to illustrate
> it.
>
>
>

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Thread

Type of a generic class? "Donkey Hottie" <donkey.hottie@1:261/38.remove-yy0-this> - 2012-08-03 18:54 +0000
  Re: Type of a generic class? "Lew" <lew@1:261/38.remove-yy0-this> - 2012-08-03 18:54 +0000
  Re: Type of a generic class? "markspace" <markspace@1:261/38.remove-yy0-this> - 2012-08-03 18:54 +0000
    Re: Type of a generic class? "Donkey Hottie" <donkey.hottie@1:261/38.remove-yy0-this> - 2012-08-03 18:54 +0000
      Re: Type of a generic class? "Lew" <lew@1:261/38.remove-yy0-this> - 2012-08-03 18:54 +0000
      Re: Type of a generic class? "markspace" <markspace@1:261/38.remove-yy0-this> - 2012-08-03 18:54 +0000
        Re: Type of a generic class? "Donkey Hottie" <donkey.hottie@1:261/38.remove-yy0-this> - 2012-08-03 18:54 +0000
  Re: Type of a generic class? "Donkey Hottie" <donkey.hottie@1:261/38.remove-5qr-this> - 2012-08-04 18:41 +0000

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