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From: Kevin Nathan <knathan@project54.com>
Newsgroups: comp.lang.java.databases
Subject: Re: Local database library
Date: Tue, 1 Oct 2013 15:41:57 -0700
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On Tue, 01 Oct 2013 17:38:01 -0400
Arne Vajh=C3=B8j <arne@vajhoej.dk> wrote:

>On 10/1/2013 4:52 PM, Kevin Nathan wrote:
>> I'm a Java newbie, but have been programming for many years. I'm
>> converting an existing application from C++ to Java. In an effort to
>> clean it up a bit, I would like to build a local library of database
>> access routines because right now everyone does their own connecting
>> and SQL writing, with way too much duplication.
>
>Create one or more classes that in more or less OOP style encapsulate
>the JDBC code.
>
>That should not be much different between Java and C++.
>

It's not, and that is what I am doing now, but at present it needs to
be copied into source files (at least, that's what the other
developers have done -- I'm trying to find a better way). I am more
interested in learning about the file structure I would use for a
library. I think I have it started, but a tutorial on building a
library from scratch would be advantageous at this point. It's a lot of
trial and error right now from the little bit of info I have found on
the internet.


>Often in Java you would not use JDBC and SQL but instead an ORM,
>given a time crunch that may not be an option for you even if the
>task at hand leaned towards it (and that is not give since you
>did not specify what you are working on).
>

I am a self-taught programmer and have never been involved with an ORM
so that's another whole level of instruction I will need! :-) I am
using NetBeans and that is helping a bit. But again, a tutorial on
building a Java library would be the best. This is the best I've found
on that, so far:

http://stackoverflow.com/questions/6205483/creating-accessing-libraries-in-=
netbeans

which is why I am still doing a lot of trial and error.

We have about 30 tables in the database (for livestock auction markets)
and I want to be able to just call a function from the main programs to
get the data, like:=20

  getTransData()
  getBuyerData()...

instead of having this in the main file:

try {
    Statement st =3D (Statement) con.createStatement();
    String command =3D
    "SELECT "
      + "SELLERID, HEAD, DESCRIP, "
      + "ROUND(WEIGHT/HEAD) AS AVG_WGT, "
      + "WEIGHT, BUYERID, PRICE, BUYERPEN, "
      + "(SELECT name FROM seller "
      + "WHERE date=3D(SELECT MAX(start) FROM sales WHERE sel=3D1) "
      + "AND number=3Dtrans.sellerid) AS NAME, "
      + "(SELECT GROUP_CONCAT(tag_num) FROM backtags "
      + "WHERE trans_id=3Dtrans.trans_id and ckin_date=3D"
      + "(SELECT MAX(start) FROM sales WHERE sel=3D1)=20
      + "GROUP BY trans_id) AS ALLTAGS "
      + "FROM trans "
      + "WHERE TRANS_ID =3D '" + transNum + "' "
      + "AND date=3D(SELECT MAX(start) FROM sales WHERE sel=3D1)";
    ResultSet rs =3D st.executeQuery(command);=20
} else {
    return;
}

So, I know what I *want* to do, just not the best way to do it in Java.
If that makes any sense.


--=20
Kevin Nathan (Arizona, USA) =20
Linux is not a destination, it's a journey -- enjoy the trip!

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