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From Thomas Fischer <tfisc...@apache.org>
Subject RE: SetByName, SetByPeerName, SetByPostion support / Generic String to Column Object utility class.
Date Thu, 15 Jun 2006 15:36:34 GMT
Thanks a lot for your explanation, now I see what you have in mind.

My current feeling is that this is outside the scope of Torque. I do not 
see any additional benefit to include the ColumnValueConverter into Torque 
as compared to using it standalone. It is not the job of a Object 
relational mapper to provide String representations of objects; there are 
other libraries which do this, e.g. jakarta common's betwixt.

    Thomas

On Mon, 5 Jun 2006, Greg Monroe wrote:

>
>
>> -----Original Message-----
>> From: Thomas Fischer [mailto:tfischer@apache.org]
>>
>> Greg, I like the first improvement and think it will improve Torque.
>
> Kewl.. It's about ready to go except for packaging and testing against
> the SVN repository head code.
>
>> I have read the second improvement thrice now but still do
>> not understand what it does and what it is for. Can you
>> please enlighten us earth-bound spirits by giving some example ?
>>
> Don't you mean straighten out my confusing.. in a hurry to finish this
> ... end of note verbage?  LOL
>
> First, I think I need to revise the potential class / method
> signatures: ( FWIW: I'm still trying to find good name...)
>
> public class ColumnValueConverter {
>
>  public static parseColumnObject( ColumnMap cMap, String Value);
>
>  public static toString( ColumnMap cMap, Object value );
>
> }
>
> Here's an example using my specific need for this.  (You guessed it)...
> doing XML imports using the Torque generated DTD.  So, for example, I
> might have have records represented in XML like the ones below that
> need to be parsed and converted to a list of OM classes that my
> application can process.
>
> <dataset name="default">
>  <UserTable UserId="bob" Password="thePenguin" ClientId="101"
>     Expires="1 Jan 2007 00:00:00 EST" Rate="99.99"
>     Disabled="false"/>
>  <RolesTable UserId="bob" RoleId="student" CourseId="666"/>
> </dataset>
>
> Parsing the XML will get string representations of the Torque DB name,
> e.g. default; Table Name(s), e.g. UserTable; Column names, e.g. UserId;
> and values, e.g. bob.  Converting these String values into an OM class
> needs some XML Parser code (sans a lot of error checking) like:
>
> public void startElement(....
>
>    if ( rawname.equals("dataset") {
>        String dbName = attributes.getValue("name");
>        dbMap = Torque.getDatabase(dbName);
>        dbMap.initialize();
>    } else {
>       String table = rawName;
>       TableMap tMap = dbMap.getTable(table);
>       BaseObject record = tMap.getOMClass().newInstance();
>       for ( int i=0; I < attributes.getLength(); i++)
>         String columnName = attributes.getQName(i);
>         String value = attributes.getValue(i);
> // getColumnByJavaName searchs thru Columns[] to find match...
>        ColumnMap cMap = getColumnByJavaName(columnName)
>
> //*****************
> // *** Need to convert String to Column Appropriate object.
> //*****************
>        Object oValue =
>            ColumnValueConverter.parseColumnObject(cMap, value);
>
>        record.setByName(columnName, oValue);
>      }
>      recordList.add(record);
>   }
> }
>
> Having a ColumnValueConverter class will centralize all the
> logic needed to convert between String data representations and
> column specific object types (e.g. Date, Boolean, Float, and the
> like).
>
> I have used an XML import example, but I can see it being used in
> many different application needs.. e.g. Import/Export using Comma
> Separated Values format or processing a web form request that needs
> to return more than String values.
>
> Another possible use for it is to improve the way that default values
> get set from the default XML schema attribute.  E.g., have you ever
> tried to define a default value for a Date field?  You have to use
> long integer milliseconds format to get it to work.  Not nice.
>
> On the output side, having a central object that generates consistant
> string representation of data is also useful.  E.g., always generating
> true / false for booleans, or Numeric field strings with the right
> precision and scale, and the like.
>
> In addition, I can see the need for dealing export and import of
> binary data (e.g., picture Blob of user).  This might be a good place
> to have "safe string" encode/decode methods, e.g. Hex and/or base64
> encoding support.
>
> Well hopefully this is clearer and better stated.
>
> Greg
>
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