Resolve the error: org.apache.ibatis.binding.bindingexception

Project scenario ：

I'm learning mybatis This problem occurred during the agent development of

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Problem description

I'm learning today mybatis There was a mistake ：

Exception in thread "main" org.apache.ibatis.binding.BindingException: Type interface com.wxy.dao.UserMapper is not known to the MapperRegistry.
	at org.apache.ibatis.binding.MapperRegistry.getMapper(MapperRegistry.java:47)
	at org.apache.ibatis.session.Configuration.getMapper(Configuration.java:745)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper(DefaultSqlSession.java:292)
	at com.wxy.service.ServiceDemo.main(ServiceDemo.java:31)

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Cause analysis ：

1. We need to know that this sentence means Yours Mapper Interface , By Spring After injection , But it can't be used normally mapper.xml Of sql;

2. there Spring After injection, it means , Your interface has been successfully scanned , But when Spring Try injecting a proxy （MyBatista Realization ） After the implementation class of , But it doesn't work . There are several possible situations here ;

① The interface has been scanned , But the proxy object was not found , Even if you try to inject , Also inject a wrong object （ It could be null）
② The interface has been scanned , Proxy object found , Also injected into the interface , But when calling a specific method , But I can't use （ Maybe other methods are normal ）

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Solution ：

How to solve ？

1. Check your mapping file for namespace Is it consistent with the path of the interface file

For example, the fully qualified name of your interface is com.dao, Class called UserDao, Then in your mapping file namespace The parameter of should be com.dao.UserDao

【 Be careful ： The path to direct replication is com/dao/UserDao.java  This is not allowed , Only use . Connect 】

2. Check your mapping file for id Is it consistent with the method name in the interface ？

For example, your method is named findAll(), Then in your mapping file id It needs to be findAll

3. Check whether the output of your interface is consistent with yours resultType Agreement ？

Such as your resultType yes user class , Then the output of your interface 【 Suppose the method in your interface is List<xxx> findAll() ;】 That is, here you are xxx Need to be User

Pay attention , I'm going to use User Because I have renamed it in the core configuration file , So if you didn't rename , Yours resultType It needs to be the package name +User, Then your output inside xxx Still User Can , It won't make any difference

Give me a screenshot

① There is no core profile custom alias

② Customize the alias

 

 ​​​​​​​ 4. Check the input of your interface and your paramType Is it consistent ？

【 Suppose the method in your interface is List<User> findAll(xxx) ;】, The mapping file is paramType="int", So you have xxx Need to be int i【 This parameter is arbitrary , As long as the parameter type is int Just go 】

I hope it helps you ！

I wish you a job soon ！ Come on together ！