不能直接遍歷map么？

我看了下網上的，只能使用嵌套的方式

聲明一個value為map的map，然后在foreach的時候

collection="key"

比如

????public?static?void?main(String[]?args)?{
????????MybatisDao?dao?=?new?MybatisDao();
??????Map<String,Map<String,Integer>>?map?=?new?HashMap<>();
????????Map<String,Integer>?map1?=?new?HashMap<>();
????????map1.put("aaa",1);
????????map1.put("bbb",2);
????????map.put("first",map1);
????????List<Message>?lis?=?dao.queryMessageByMap(map);
????}

????public?List<Message>?queryMessageByMap(Map<String,Map<String,Integer>>?params){
????????DBAccess?dbAccess?=?new?DBAccess();
????????SqlSession?sqlSession?=?null;
????????List<Message>?messageList?=?null;
????????try?{
????????????sqlSession?=?dbAccess.getSqlSession();
????????????messageList?=?sqlSession.selectList("Message.selectMap",params);
????????}?catch?(IOException?e)?{
????????????e.printStackTrace();
????????}
????????return?messageList;
????}

對應的mapper中的sql：
<select?id="selectMap"?parameterType="map"?resultType="com.imooc.bean.Message">
????select?ID,COMMAND,DESCRIPTION,CONTENT?from?message?WHERE?id?IN
????????<foreach?collection="first"?index="index"?item="value"?open="("?close=")"?separator=",">
????????????#{value}
????????</foreach>
</select>

有能直接就遍歷的方法么？