Re: Field length control

[Gus Heck]

What I seem to have found regarding this is that OJB wants you to tell 
it what the field length is in the database, and this is not related to 
any of the JDO api or the .jdo files. If you want to determine the field 
length outside of your database, you need to use Torque or some other 
tool to push the database schema into the db. Currently I am doing this 
by using Xdoclet to generate a torque style xml schema for my database, 
though you can certainly code one by hand too. The JDO stuff is not 
related, and does not change OJB's understanding of what is in the 
database (which sits behind the JDO API). The JDO API wraps the existing 
OJB mechanisms.

You may wish to check out this link which will point you at a variety of 
options for working with OJB including xdoclet:

http://db.apache.org/ojb/howto-build-mappings.html

The xdoclet task for ojb is in the contrib directory of the ojb source 
download. I have heard that it will eventually become part of the 
xdoclet distro, but this has not yet happend as far as I know.

The reason I chose xdoclet is cause It will generate, the JDO 
descriptors, the torque schema and the repository.xml from a class that 
looks like this:

/**
* The actual data that needs to be persisted for a location.
*
* @ojb.class     
* @jdo.persistence-capable
*/
public class LocationBase implements Location {
  
   /**
    * @ojb.field primarykey="true"
    */
   Integer id;
   /**
    * @ojb.field length="40"
    */
   String country;
   /**
    * @ojb.field length="60"
    */
   String stateOrRegion;
   /**
    * @ojb.field length="60"
    */
   String subRegion;
   /**
    * @ojb.field length="60"
    */
   String city;

(Rest of class is irrelevant)

in my Ant build I use a target like:

<!-- ==================== Xdoclet OJB stuff 
================================== -->

   <target name="repository-files"  depends="init">
       <taskdef name="ojbdoclet" 
classname="xdoclet.modules.ojb.OjbDocletTask">
          <classpath refid="compile.classpath"/>
       </taskdef>

       <ojbdoclet destdir="${build.home}/WEB-INF/classes/">
           <fileset dir="./src" excludes=".nb*"/>
           <ojbrepository destinationFile="repository_user.xml"/>
           <torqueschema databaseName="fdbtest2" 
destinationFile="project_schema.xml"/>
       </ojbdoclet>
   </target>

I get an entry for Country that looks like this in my 
repository_user.xml file:

   <field-descriptor
       name="country"
       column="country"
       jdbc-type="VARCHAR"
       length="40"
   >
which matches this entry in my project_schema.xml:

       <column name="country"
               javaName="country"
               type="VARCHAR"
               size="40"
       />
This puts the information in one place. which is very nice and easy to 
maintain.

-Gus

Emmanuel Dupont wrote:

All,



What is the best solution to control the field length of a JSP application
with OJB.


The repository. Xml doesn't contain any information about the database field
length.


Anyway if it would do it, I would have the same trouble. All the jdo
attribute I use are String, etc.and in database I have Varchar(20), Varchar
(4) etc..




Any help, please...









 



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