Map containing Lists of Maps

Gary Bradshaw Wed, 09 Nov 2005 08:16:40 -0800

My compliments on a most useful product. I'm always thinking about ways to improve the signal-to-noise ratio in business software, and SqlMaps seems like a simple way to reuse a wide variety of familiar real-world Java objects by linking them directly to SQL parameters and results.

One of the first things to catch my eye was the ability to use Maps as parameters and result sets. I realize that a lot of the time you need a level of indirection between Java objects and SQL fields, and JavaBeans are a fine place for it, but if you don't need the indirection at this level in your architecture, usings Maps instead of JavaBeans could save a lot of otherwise useless code made up of nothing but thousands of getter and setter methods.

I tried a 1:N select the non-join way, and I found that everything worked as advertised when I mapped my primary result set to a Bean class. But when I tried to map it to a java.util.Map, I couldn't get iBatis to return the secondary objects as a java.util.List, even though I specified a javaType attribute in the primary result map. Can anyone tell me what I did wrong? Can I put a "[]" someplace or something?

<?xml version="1.0"?>
<!DOCTYPE sqlMap PUBLIC
"-//iBATIS.com//DTD SQL Map 2.0//EN"
"http://www.ibatis.com/dtd/sql-map-2.dtd">


<sqlMap>
    <resultMap id="mapUserObject" class="Release">
        <result property="id" column="ID"/>
        <result property="description" column="DESCRIPTION"/>
        <result property="application" column="APPLICATION"/>
        <result property="version" column="VERSION"/>
        <result property="issueList" column="ID" select="getIssues"/>
    </resultMap>
    <resultMap id="mapToMap" class="java.util.HashMap">
        <result property="id" column="ID"/>
        <result property="description" column="DESCRIPTION"/>
        <result property="application" column="APPLICATION"/>
        <result property="version" column="VERSION"/>
        <result property="issueList" column="ID" select="getIssues"
         javaType="java.util.ArrayList"/>
    </resultMap>
    <select id="getNestedObjects" parameterClass="int"
     resultMap="mapUserObject">
        SELECT ID, APPLICATION, VERSION, DESCRIPTION FROM TEST.RELEASE
        WHERE ID = #value#
    </select>
    <select id="getNestedMaps" parameterClass="int"
     resultMap="mapToMap">
        SELECT ID, APPLICATION, VERSION, DESCRIPTION FROM TEST.RELEASE
        WHERE ID = #value#
    </select>
    <select id="getIssues" parameterClass="int"
     resultClass="java.util.HashMap">
        SELECT A.ISSUE_ID, DESCRIPTION FROM TEST.ISSUE AS A
        INNER JOIN TEST.ISSUE_RELEASE AS B ON (A.ID = B.ISSUE_ID)
        WHERE RELEASE_ID = #value#
    </select>
</sqlMap>

"getNestedObjects" works fine, but "getNestedMaps" returns a HashMap for the issueList property instead of an ArrayList, or it fails with "executeQueryForObject returned too many results" when there is more than one issue for a release. I read the documentation several times and I can't find anything that says that this shouldn't work, but I can't seem to make it happen.

Thanks in advance.

- gary
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Map containing Lists of Maps

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