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From Stefan Langer <mailtolan...@googlemail.com>
Subject How to handle null objects in nested ResultMaps
Date Wed, 29 Nov 2006 16:13:16 GMT

I new to IBatis and for a small project of mine I'm using only the 
datamapper framework from Ibatis.

I have a fairly simple data structure where a notebook contains several 

For simplicity assume this domainmodel:

Notebook           Page
   [id]     1 -> N   [id]

The corresponding Map looks like this ( this is not a complete example 
as I only want to make clear what my situation is)

<resultMap class="notebook" groupBy="id" id="notebookResult">
    <result column="NB_ID" jdbcType="VARCHAR" property="id"/>
    <result javaType="java.util.List" property="pages" 

<resultMap class="page" groupBy="id" id="pageResult">
   <result column="P_ID" jdbcType="VARCHAR" property="id"/>

I'm using the following select statement to get the notebooks and 
corresponding pages

<select id="selectNotebook" parameterClass="java.lang.String" 
SELECT nb.id as nb_id, p.id as p_id, 	
FROM notebook nb LEFT JOIN page p ON nb.id = p.notebook_id
WHERE nb.id = #id#

When I have a notebook that has no pages IBatis sets a page object with 
ID = null in the pages property of notebook.
I need to get notebooks that do not have pages but in those cases I do 
not wish to have a page object at all.

Is there an easy way around this situations? I have tried to Google and 
looked at the archive but all the threads that I found dealing with this 
didn't give me any information on how this is solved.

Thanks for any help


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