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From Clinton Begin <clinton.be...@gmail.com>
Subject Re: java.util.HashMap as resultClass
Date Mon, 24 Jan 2005 21:58:24 GMT
Final point:

Most any POJO that I can imagine is cheaper to serialize than any
typical Map implementation.  This stands to reason simply based on
that a serialized Map must contain both the metadata and the data...a
serialized POJO (JavaBean) only needs to save the data.

Cheers,
Clinton


On Mon, 24 Jan 2005 13:46:52 -0800, Pascal DeMilly
<list.ibatis@newgenesys.com> wrote:
> Prashanth.
> 
> This is exactly what and why I am implementing it. Basically since my
> application would be remote to my business and DAO layer, I need to
> simplify the exchange. Moving the whole set of POJO just to get the ID
> and name doesn't seem efficient. My choice of keywords was certainly the
> best. I tried using key/value (I used to be a Smalltalk developer) but
> SQL didn't like that. I was going to use MapKey and MapValue as a
> replacement.
> 
> Contrary to Clinton remarks, I don't think I have brought my
> presentation layer into my persistance layer, since the keywords
> (ID=>name or MayKey,MapValue) are only a contract between the DAO and
> the SqlMap.
> 
> When it gets to the presentation layer or actually even the business
> logic layer, it is just a Map of object key/value with no reference to
> the key/value keyword used in the DAO layer.
> 
> On Mon, 2005-01-24 at 12:44, Prashanth Sukumaran wrote:
> > Hi Pascal,
> >
> > I think i understand what Brandon is trying to say. He is talking about using the
right pattern
> > for the kind of job you are trying to achieve.
> >
> > If my guess is right. Looks like you trying to do this for your dropdowns.  I do
it this way and i
> > feel it is much cleaner this way.
> >
> >
> > public interface ValueObject{
> >
> >     /**
> >      * Gets the iD attribute of the KeyValueObject object
> >      *
> >      * @return   The iD value
> >      */
> >     String getID();
> >
> >     /**
> >      * Gets the value attribute of the KeyValueObject object
> >      *
> >      * @return   The value value
> >      */
> >     String getValue();
> >
> >   /**
> >    * This method returns sort field
> >    *
> >    *
> >    * @return value of sort field
> >      */
> >     public Object getSortFieldValue();
> > }
> >
> > All Objects that you are using for Dropdowns will extend the ValueObject, and they
will implement
> > the three methods.  In your case getID() will return SKU, getValue will return Description.
 and
> > for the getSortFieldValue() have an empty implementation.  This way the bean can
be used for other
> > things and also used for dropdowns.
> >
> > For the dropdowns have a common method that handles them or even struts has the
LabelValue bean.
> >
> > Rgds
> > Prashanth.
> >
> >
> > --- Pascal DeMilly <list.ibatis@newgenesys.com> wrote:
> >
> > > Well. It seems logical to me. Why would iBatis go into great length at
> > > trying to map result in the SqlMap file then if it was not to limit the
> > > knowledge of your database to that XML file. The dependency have to stop
> > > somewhere and it seems to me the SqlMap file is the place where it
> > > should stop. The DAO implementation classes should only know about the
> > > iBatis map id and its expected POJO results not how your database
> > > columns are named or it seems to me.
> > >
> > > Anyway, in my case while this solve one of my problem, queryForMap is
> > > still not as efficient as it could be since it relies on queryForList.
> > > So basically it is building two list. One with each element being a Map
> > > of column name/value, then another map of only values. Would it be more
> > > efficient to rewrite queryForMap to use a RowHandler?
> > >
> > >
> > >
> > > On Mon, 2005-01-24 at 10:15, Brandon Goodin wrote:
> > > > Why is it a problem to have a code dependency in an "implementation"
> > > > class? It is suppossed to be aware of IBatis SQLMap semantics. You
> > > > interface over your DAO class should hide the specifics of your
> > > > implementation code within your Dao.
> > > >
> > > > Brandon
> > > >
> > > >
> > > >
> > > >
> > > > On Mon, 24 Jan 2005 09:22:49 -0800, Pascal DeMilly
> > > > <list.ibatis@newgenesys.com> wrote:
> > > > > Thanks Larry,
> > > > >
> > > > > I tried it and it works. However this still leave some dependencies
in
> > > > > my DAO code as I have to specify the column names there as in:
> > > > >
> > > > > return getSqlMapClientTemplate().queryForMap("getItemNameMap", null,
"SKU", "Description");
> > > > >
> > > > > How will you do about moving that code into the SqlMap. Should I
create
> > > > > a custom resultMap with key/value as properties and refer to it in
my
> > > > > DAO code?
> > > > >
> > > > > I am going to give it a try and see what happened.
> > > > >
> > > > > Thanks for you help.
> > > > >
> > > > > Pascal
> > > > >
> > > > > On Mon, 2005-01-24 at 08:44, Larry Meadors wrote:
> > > > > > Try executeQueryForMap() instead.
> > > > > >
> > > > > >
> > > > > > On Mon, 24 Jan 2005 08:42:25 -0800, Pascal DeMilly
> > > > > > <list.ibatis@newgenesys.com> wrote:
> > > > > > > Hi,
> > > > > > >
> > > > > > > I would like to retrieve a Map with whose key is the 1st
column of my
> > > > > > > query and the value is the 2nd column. For example right
now I do:
> > > > > > >
> > > > > > > <select id="getItemNameMap" resultClass="java.util.HashMap">
> > > > > > >         select SKU, Description from Items
> > > > > > > </select>
> > > > > > >
> > > > > > > However this returns a list of maps with the key being
the column name
> > > > > > > and the value the column value which seems wasteful in
term of space (I
> > > > > > > am using remoting to retrieve that info).
> > > > > > >
> > > > > > > I currently solve it by using a custom rowHandler in my
DAO as follow:
> > > > > > >
> > > > > > >     public Map getItemNames () throws DataAccessException
{
> > > > > > >         final KeyValueHandler rowHandler = new KeyValueHandler
();
> > > > > > >         getSqlMapClientTemplate().queryWithRowHandler("getItemNameMap",
null,
> > > rowHandler);
> > > > > > >         return rowHandler.getMap();
> > > > > > >     }
> > > > > > >
> > > > > > >     private class KeyValueHandler implements RowHandler
{
> > > > > > >         final Map map = new HashMap ();
> > > > > > >
> > > > > > >         public void handleRow(Object valueObject) {
> > > > > > >             final Map row = (Map) valueObject;
> > > > > > >             map.put (row.get("SKU"), row.get("Description"));
> > > > > > >         }
> > > > > > >
> > > > > > >         public Map getMap () {
> > > > > > >             return map;
> > > > > > >         }
> > > > > > >
> > > > > > >     }
> > > > > > >
> > > > > > > But I would like to move possibly that code out of my DAO
code and into
> > > > > > > iBatis SqlMap file.
> > > > > > >
> > > > > > > How could I do that
> > > > > > >
> > > > > > > TIA
> > > > > > >
> > > > > > > Pascal
> > > > > > >
> > > > > > >
> > > > >
> > > > >
> > >
> > >
> >
> >
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>

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