MyBatise传入带list集合或数组的map参数问题记录'cardnums' evaluated to a null value

项目中遇到一个需求，查询条件里有一个是下拉复选，需要在map集合里传一个list或者数组，总结一下

1，传一个普通的map

java代码里

HashMap<String,Object> map = new HashMap<String, Object>();
map.put("gender", "男");
map.put("name", "a");

xml里接收

<select id="findUser" parameterType="Map" resultType="user">
    select from user
    where 
    1=1
    <if test="gender !=null and gender !=''">
        and gender = #{gender}
    </if>
    <if test="name !=null and name !=''">
        and name = #{name}
    </if>
</select>

2，传一个数组

java

String arrayIds[] = {"1","3","5"};

xml

<delete id="deleteAll" parameterType="String">
        delete from
        user
        where
        id in
        <foreach item="item" index="index" collection="array" open="(" separator="," close=")">
        #{item}
        </foreach>
</delete>

item名称可以自定义，collection名称传入数组时固定为'array'

3，传入list集合

java

List<String> ids = Arrays.asList("1","2","3");

xml

<delete id="deleteByIds" parameterType="java.util.List">
        delete from
        user
        where
        id in
        <foreach item="item" index="index" collection="list" open="(" separator="," close=")">
        #{item}
        </foreach>
</delete>

这里跟传入数组差不多，不过list集合在mybatis里的key是'list'

3，传入带数组或list的map集合

java

HashMap<String,Object> map = new HashMap<String, Object>();
String cardnums[] = {"001","002","005"};
List<Sring> ids = Arrays.asList("1","2","3");
map.put("gender", "男");
map.put("cardnums",cardnums);
map.put("ids",ids);

xml

<select id="findUser" parameterType="map" resultType="user">
    select from user
    where 
    1=1
    <if test="gender !=null and gender !=''">
        and gender = #{gender}
    </if>
    <if test="cardnums !=null and cardnums.size() >0">
        and cardnum in
        <foreach collection="cardnums" item="num" index="index" open="(" separator="," close=")">
        #{num}
        </foreach>
    </if>
    <if test="ids !=null and ids.length >0">
        and id in
        <foreach collection="ids" item="id" index="index" open="(" separator="," close=")">
        ${id}
        </foreach>
    </if>
</select>

执行这一段的时候发现始终没有进去数组部分的判断条件，删除判断空数组的控制再尝试后，有报错提示

'cardnums' evaluated to a null value

查找原因后发现mybatis不支持map传数组参数，需要把数组转换成list

map传list参数有几个注意点

1. 以map参数的形式传入数组和list集合，此时collection里的key为map集合里定义的key
2. list遍历时用的是${itemName} 或者#{listName}[index]