問題描述：寫了一個BillMapper.xml檔案，相應的寫了一個dao層操作介面BillMapper.java介面，全部寫完ok，在測試類中測試，執行後console視窗報以下異常：

org.apache.ibatis.binding.BindingException:
Type interface com.testmybatis.dao.bill.BillMapper is not known to the
MapperRegistry.

      at
org.apache.ibatis.binding.MapperRegistry.getMapper(MapperRegistry.java:42)

      at
org.apache.ibatis.session.Configuration.getMapper(Configuration.java:639)

      at org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper(DefaultSqlSession.java:218)

      at com.testmybatis.test.BillTest.test3(BillTest.java:75)

      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

      at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)


 

  異常的字面意思是com.testmybatis.dao.bill型別介面。MapperRegistry不認識BillMapper。通過字面意思覺得應該是mapper.xml檔案未被配置，遂去mybatis-config.xml下去檢視<mappers>元素中的mapper對映

<mappers>

       <mapper resource="com/testmybatis/dao/UserMapper.xml"></mapper>

       <mapper resource="com/testmybatis/dao/provider/ProviderMapper.xml"></mapper>

       <mapper resource="com/testmybatis/dao/bill/BillMapper.xml"></mapper>

    </mappers>


 

，發現對映路徑無誤，正納悶問題出在哪裡呢，遂靈機一動，即然對映路徑沒錯，會不會是BillMapper.xml的namespace命名空間出錯了呢？果然：

由於之前加過一層包，導致了namespace配置的和包的路徑不一致，改為正確的路徑後
 執行正常