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From Brice Ruth <bdr...@gmail.com>
Subject Re: java.util.HashMap as resultClass
Date Mon, 24 Jan 2005 21:21:34 GMT
For the record, this recommendation is far better than using a
LabelValueBean in iBATIS SqlMaps ... I still do it, because its easy,
but Clinton's suggestion is far superior :)


On Mon, 24 Jan 2005 14:04:42 -0700, Clinton Begin
<clinton.begin@gmail.com> wrote:
> Pascal,
> 
> Another approach is to use a wrapper class at your presentation layer.
>  After all, this is a presentation layer problem, that is probably
> best solved in the presentation layer -- not in the persistence layer.
> 
> By aliasing your columns to ID and Value, you've made a change to your
> persistence for the sake of a presentation requirement.
> 
> Here's my recommendation:
> 
> 1) Use a real domain model.  Avoid Maps.  Create a real class that
> represents your domain.  In this case it looks like a Product class or
> something (with properties such as  SKU, Description etc.)
> 
> 2) Map that class with iBATIS properly, using a real parameter class
> and result class, with columns mapped to the JavaBean properties.
> 
> 3) Use that domain object throughout your application.  When a
> requirement such as a droplist manifests itself, use a wrapper class
> to manage special behavior.  For example, given a Product class, you
> could have a ProductDropListItem that knows how to provide the
> appropriate identifier and value to the drop list.
> 
> Don't worry about having to make a matching DropListItem for each
> class.  It's very easy to make a generic one that will work with any
> domain class (passed into the constructor).  E.g. new DropListItem
> (aProduct).
> 
> This keeps presentation layer problems out of the persistence layer.
> It's also pretty easy to implement.
> 
> Cheers,
> Clinton
> 
> On Mon, 24 Jan 2005 12:44:27 -0800 (PST), Prashanth Sukumaran
> <prashanthsukumaran@yahoo.com> 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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