"Type class is not known to the MapperRegistry" in MyBatis - mybatis

Question

My Problem
I'm getting the error Type class myPackage.MyClass is not known to the MapperRegistry.
I successfully acquired a session, and upon debugging I can see that it otherwise appears to be configured correctly so the interface association seems to be working; therefor I'm confident this error is distinct from the stack-overflow-suggested Type interface is not known... question.
I'm new to myBatis but from the documentation I understood that the following was all that was required to get resultType auto-mapping to work.
Update: This also happens when mapping the mapper resources by xml file instead of by class.
My Mapper
public interface MyClassMapper{
MyClass getMyClass(Integer id);
}
My Model
public class MyClass{
private String itemValue;
public String getItemValue() {
return itemValue;
}
public void setItemValue(String itemValue) {
this.itemValue = itemValue;
}
}
My Sql Map
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="myPackage.orm.sqlMap.MyClassMapper" >
<select id="getMyClass" resultType="myPackage.MyClass" >
select itemValue
from SOME_TABLE
WHERE id = #{id}
</select>
</mapper>
My mybatis-config.xml
...
<mappers>
<mapper class="myPackage.MyClass" />
</mappers>
...

Answer 1

Fixed:
public MyClass getMyClassValue(Integer id) throws Exception{
SqlSession session = MyBatisSessionFactory.openSession();
MyClassMapper mapper = (MyClassMapper) session.getMapper(MyClass.class);
return mapper.getMyClass(id);
}
Here is the code I was using to execute the query, discovered that I was looking up the mapper in the mapper registry by the model class name, rather than the mapper interface name. Works just fine now.

Answer 2

In your mapper.xml file mapper's namespace should be the path to the mapper interface.
for example:
<mapper namespace="com.mapper.LineMapper">
<select id="selectLine" resultType="com.jiaotong114.jiaotong.beans.Line">
select * from bus_line where id = #{id}
</select>
</mapper>
your mapper interface should be in com.mapper package and the name of it is LineMapper.
hope help.

Answer 3

I solved this issue by adding the mapper XML to the mybatis xml configuration file
<mappers>
<mapper resource="com/java/Mapper.xml"/>
</mappers>