Velocity Reviews

Velocity Reviews (http://www.velocityreviews.com/forums/index.php)
-   Java (http://www.velocityreviews.com/forums/f30-java.html)
-   -   Dynamicly generate class from foreign key lookup table, referencevalues (http://www.velocityreviews.com/forums/t633379-dynamicly-generate-class-from-foreign-key-lookup-table-referencevalues.html)

Adam 09-02-2008 04:59 PM

Dynamicly generate class from foreign key lookup table, referencevalues
 
Hello,

I'm generally new to Java and have a project where I've got a db
schema with normalized reference tables with static/readonly lookup
values.. I've also generated a Bean mapping from the overall schema
and was wondering how to tag(?) or annotate the reference types
(corresponding to the normalized reference/lookup tables) with their
readonly content, for example:
table:
FK_Ref_Table1
"SomeKey", "Value"
"SomeOtherKey", "someOtherValue"
....

And in the mapped bean class
FK_Ref_TableObject.SomeKey
FK_Ref_TableObject.SomeOtherKey
....
where these object.property resolves to the "Value" and
"someOtherValue" ...
What I'd like to avoid is hard-coding the keys into the project but to
be able to reference them as a class; and without having to hard-code
the class... a data access layer might provide inserts, updates, etc.
to the FK reference values which would then reflect in the generated
class, automatically.

Not even sure what to call what I'm talking about.


Thanks for any help.

Stefan Ram 09-02-2008 05:10 PM

Re: Dynamicly generate class from foreign key lookup table, reference values
 
Adam <meyer.adam@gmail.com> writes:
>Not even sure what to call what I'm talking about.


You can write and load a class file at run-time.

In this case, you should adhere to the Java Class file format:

http://java.sun.com/docs/books/jvms/...sFile.doc.html

However, it usually is recommended to use code (classes) for
everything static (things that never change at run time,
that never change during the lifetime of the software).

What changes at run time is considered to be data.

Data is handled by the dynamic means intended for it,
for example container objects and so.

So your program would read the scheam from the DB and then
build everything it needs at run time from the schema as data,
not as classes. When the schema changes, it re-reads it and
re-builds what needs to be rebuilt.

For example, when you want to convert from Celsius to
Fahrenheit, and the user has input the value 32, you store
this in a variable and then use it. You do not generate a
class with this value, then load the class and use it.


dontlikenicknames 09-02-2008 06:20 PM

Re: Dynamicly generate class from foreign key lookup table, referencevalues
 
Sounds like a great candidate for Hibernate. If you're new to Java,
you can check out their site at http://www.hibernate.org/. I'm not
sure how complicated your project is, but hibernate will do exactly
what I think you are looking to do...Load DB values into POJOs, and
vice versa?

The basic concept is that you map out your DB to Java objects in an
XML document and Hibernate takes care of a lot of the details for you.

Hope I helped.

--
Michael
http://javaconfessions.blogspot.com


All times are GMT. The time now is 07:33 PM.

Powered by vBulletin®. Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO ©2010, Crawlability, Inc.