Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for**

mybatis初学的异常如下

在出现该异常时大体意思为：

###查询数据库时出错。原因：java.lang.illegalargumentException:映射语句集合不包含tk.mybatis.simple.mapper.countrymapper.selectAll的值

###原因：java.lang.illegalargumentException:映射语句集合不包含***

及找不到所对应的mapper.xml文件，在mybatis-config.xml文件中的mappers标签中看是否写入了mapper文件。比如：

<mappers>
        <mapper resource="tk/mybatis/simple/mapper/CountryMapper.xml"></mapper>
</mappers>

Error querying database. Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for tk.mybatis.simple.mapper.CountryMapper.selectAll

Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for tk.mybatis.simple.mapper.CountryMapper.selectAll