Mybatis 异常 Error Type interface com.wanghwei.dao.IUserDao is not known to the MapperRegistry 或者 Could not find resource *

1.Error

对于新手来说也许会遇到的问题

 

 

 

解决方案

配置mybatis-config.xml ---><mapper>

代码:

<mappers>
    <mapper resource="src/main/resources/mapper/UserMapper.xml"/>
</mappers>

之后测试又报错,说是没有找到src/main/resources/mapper/UserMapper.xml。

我遇到的是俩个问题：

1.首先要配置pom.xml，如果有父子工程最好都配置上，一般正常情况下只配置父工程就可以了

<build>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
    </resources>
</build>

2.对于新手来说可能会遗忘resources是maven默认配置文件，所以不需要在<mapper resource="src/main/resources/mapper/UserMapper.xml"/>配置完整的路径，只配置resources下面的路径就可以了,对于我自己的项目正确路径是mapper/UserMapper.xml。

 

解决问题

我的项目结构

 

 

2.Error

org.apache.ibatis.binding.BindingException: Type interface com.wanghwei.dao.IUserMapper is not known to the MapperRegistry.

 

 问题原因

 

 

3.Error

org.apache.ibatis.binding.BindingException: Type interface com.wanghwei.dao.IUserMapper is not known to the MapperRegistry.这个错误的原因是<mapper>中  namespace的命名空间有误

4.Error

Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'mapper/UserMapper.xml'. Cause: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for com.wanghwei.dao.IUserMapper.getUserList. please check mapper/UserMapper.xml and mapper/UserMapper.xml 

这个是由<select>中的id 方法名重复使用,在错误信息中就可以看出来