如何在MyBatis foreach中迭代HashMap？

Question

I'm trying to produce a sql which is as below in mybatis.

SELECT COL_C
FROM TBLE_1
WHERE (COL_A, COL_B) in ( ('kp','kar'),('srt','sach'));

And my input parameter type is HashMap. Now How do I generate SQL from mapper xml file. The below code throws exception saying map evaluated to null.

<select id="selectCOLC" parameterType="java.util.HashMap" resultType="String">
    SELECT COL_C
    FROM TBLE_1
    WHERE (COL_A, COL_B) in 
    <foreach item="item" collection="#{map.keySet()}" open="((" separator="),(" close="))">
        #{item},#{item.get(item)}
    </foreach>
</select>

One of the other approach is to create a class with key value fields, create a list of object and then pass the parameterType as list which would look like following.

<select id="selectCOLC" parameterType="list" resultType="String">
        SELECT COL_C
        FROM TBLE_1
        WHERE (COL_A, COL_B) in 
        <foreach item="item" collection="list" open="((" separator="),(" close="))">
            #{item.getKey()},#{item.getVal()}
        </foreach>
    </select>

But is there any way to my mapper work for the first approach? other than changing the query to union

Answer 1

This solution doesn't work since version 3.2 - see more in Issue #208 !

Finally I've the solution for HashMap

I Should use entrySet() in order to make it iteratable

<select id="selectCOLC" parameterType="map" resultType="kpMap">
    SELECT COL_C
    FROM TBLE_1
    WHERE (COL_A, COL_B) in 
    <foreach item="item" collection="entries.entrySet()" open="((" separator="),(" close="))">
        #{item.key},#{item.value}
    </foreach>
</select>

One more Isue I was facing parameter name was not getting injected, Hence added @Param annotation

Hence mapper interface looks like below.

List<TblData> selectCOLC(@Param("entries")
            HashMap<String, String> entries)

Answer 2

this is an example in my project and it works fine

<select id="getObject" parameterType="Map" resultType="hashmap">    
    select * from TABL where 
    <foreach  collection="dataMap"  index="key" item="value"  open=""  separator=" and "  close="">
        #{key}=#{value}
    </foreach>
</select>

Answer 3

In your first example mybatis is looking for an entry in the parameterMap with the key "map". I suspect that you are actually trying to iterate the key set of the parameterMap. If you nested the map within the parameter map using the key "map" it should work.

In the second example you should just be able to pass the HashMap.entrySet() which provides a getKey and getValue.

Answer 4

As a user of mybatis 3.5, I came through this.

Unfortunately, none of the solutions posted here worked for me but this does:

<foreach collection="_parameter.entrySet()" index="key" item="element" separator=",">
    MY_COLUMN = #{key} AND MY_OTHER_COLUMN = #{element}
</foreach>

So, in my case collection="_parameter.entrySet()" did the trick!

Moreover, none specification regarding the parameterType was needed.