Question

I am stacked. I would like to replace direct use of sql in favor of mybatis faramework.
I would like to select list of accounts with filled properties map.

But lets start from the beginning, first Account class

public class Account {
     private int id;
     ...
     private Map<String, String> properties;
     ...
     //setters / getters
}

Mapper interface for Account is obvious and mapping file contains selects

<select id="getAccountById" resultMap="account">
       select ... from account where id = #{id}
</select>

<select id="getAccountProperties" resultType=map>
       select * from properties where id=#{id}
</select>

First selection returns Account object, second java.util.Map contains column name / value pair.

I would like that each account object contain map with properties, so I iterate over list of accounts and selects its properties by id

for(Account account : accountList) {
    int id = account.getId();
    Map properites = mapper.getAccountProperties(id);
    account.setProperties(properties);
}

And basically it works, but for 200 accounts it takes about 2 minutes, and it is not acceptable.

I hope that using resultMap with collection will speed it up. But the question is how
to do it. How should resultMap="account" looks like

<resultMap id="account" type="Account">
   <id property="id" column="id">
   ...
   <collection property="properties" javaType="map" column="id" select="getAccountProperties" />
</resultMap>

In this case selected account object does not contain any properties.
The big question is: How to associate properties with account object?

Answer 1

If you use the following resultmap

<resultMap id="account" type="Account">
    <result property="id" column="id">
    <result property="properties" column="id" select="getAccountProperties" />
</resultMap>

Then for each account MyBatis executes the getAccountProperties statement passing the value of the column id as a parameter, but you must allow to accept it in the select tag:

<select id="getAccountProperties" resultClass="java.util.Map" parameterClass="java.lang.Integer" >
    select * from properties where id=#value#
</select>