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Description
This issue is based on my post https://groups.google.com/forum/#!topic/mybatis-user/Enju_-c8SbQ
Currently @mapkey cant be used for nested collections in result map. The problem is that developers put @mapkey() in interface. I dont' know why they did this but it was wrong solution as it's clear that there can be more that one Map. The solution of this problem is very simple - move MapKey from interface to resultMap so it could be used in association,collections etc.
So I suggest to make this changes in MyBatis.