“Type interface is not known to the MapperRegistry” exception using mybatis

Question

I\'m setting up mybatis using annotations, and getting this helpful exception

org.apache.ibatis.binding.BindingException: Type interface org.foo.Bar is

Answer 1

It may be that your mapper.xml file is using the incorrect namespace (perhaps because of a copy paste error).

For instance, let's say you have a Java interface called MyEntityMapper.java that should be linked to a mybatis mapper xml config called MyEntityMapper.xml:

MyEntityMapper.java

package my.mappers;

public interface MyEntityMapper {
    MyEntity getById(@Param("id") String id);
}

MyEntityMapper.xml

Notice that the namespace attribute on the element in MyEntityMapper.xml is pointing to some non-existent mapper non.existent.package.NonExistentMapper, when really it should be pointing to my.mappers.MyEntityMapper.