MyBatis - Returning a HashMap - mybatis

Question

I want the returned result of the select statement below to be Map<String, Profile>:
<select id="getLatestProfiles" parameterType="string" resultMap="descProfileMap">
select ml.layerdescription, p1.*
from ( select max(profile_id) as profile_id
from SyncProfiles
group by map_layer_id) p2
inner join SyncProfiles p1 on p1.profile_id = p2.profile_id
inner join maplayers ml on ml.LAYERID = p1.MAP_LAYER_ID
where ml.maxsite = #{site}
</select>
I have seen this post which maps a String to a custom class, but the key was part of the custom class. In my query above, the layerdescription field is not part of the Profile class since I'm aiming to have the Profile class strictly represent the syncprofiles table and the layerdescription field is in another table.
My interface looks like:
public Map<String, Profile> getLatestProfiles(final String site);
How should descProfileMap be defined? I want to do something like:
<resultMap id="descProfileMap" type="java.util.HashMap">
<id property="key" column="layerdescription" />
<result property="value" javaType="Profile"/>
</resultMap>
But this is clearly wrong. Thanks for your help!

Answer 1

Achieving this requires 2 steps:
-Use association and nested resultMap:
<resultMap type="Profile" id="profileResultMap">
<!-- columns to properties mapping -->
</resultMap
<resultMap type="map" id="descProfileMap">
<id property="key" column="layerdescription" />
<association property="value" resultMap="profileResultMap" />
</resultMap>
-Add every record to a Map with expected structure using ResultHandler:
final Map<String, Profile> finalMap = new HashMap<String, Profile>();
ResultHandler handler = new ResultHandler() {
#Override
public void handleResult(ResultContext resultContext) {
Map<String, Object> map = (Map) resultContext.getResultObject();
finalMap.put(map.get("key").toString()), (Profile)map.get("value"));
}
};
session.select("getLatestProfiles", handler);
If you run that as is, expect this exception will likely be raised:
org.apache.ibatis.executor.ExecutorException: Mapped Statements with
nested result mappings cannot be safely used with a custom
ResultHandler. Use safeResultHandlerEnabled=false setting to bypass
this check or ensure your statement returns ordered data and set
resultOrdered=true on it.
Then following the suggestion, you can either disable the check globally in Mybatis config:
According to the documentation:
safeResultHandlerEnabled: Allows using ResultHandler on nested statements. If allow, set the
false. Default: true.
<settings>
<setting name="safeResultHandlerEnabled" value="false"/>
</settings>
or specify your result is ordered in the statement:
The documentation states:
resultOrdered This is only applicable for nested result select
statements: If this is true, it is assumed that nested results are
contained or grouped together such that when a new main result row is
returned, no references to a previous result row will occur anymore.
This allows nested results to be filled much more memory friendly.
Default: false.
<select id="getLatestProfiles" parameterType="string" resultMap="descProfileMap" resultOrdered="true">
But I have not found anyway to specify this statement option when using annotations.